The unit of noise level is decibel definition. Noise, its characteristics. Measurement units of noise. How to keep your hearing

"Noise" is a disorderly mixture of sounds.

Low and high pitched sounds seem quieter than midrange sounds of the same intensity. Taking this into account, the uneven sensitivity of the human ear to sounds of different frequencies is modulated using a special electronic frequency filter, resulting in the normalization of measurements, the so-called equivalent (in energy, "weighted") sound level with the dimension dBA (dB (A), then yes - with filter "A").

A person, in the daytime, can hear sounds with a loudness and higher. The maximum frequency range for the human ear, on average, is from 20 to Hz (possible range of values: from up to 00 Hz). In youth, a mid-frequency sound with a frequency of 3 KHz is better heard, in middle age - 2-3 KHz, in old age - 1 KHz. Such frequencies, in the first kilohertz (up to Hz - the zone of speech communication) - are common in telephones and on the radio on the MW and LW bands. With age, the audible range of sounds narrows: for high-frequency sounds - decreasing to 18 kilohertz or less (in older people, every ten years - by about 1000 Hz), and for low-frequency sounds - increasing from 20 Hz or more.

In a sleeping person, the ears become the main source of sensory information about the environment ("light sleep"). Hearing sensitivity, at night and with closed eyes, increases overB (up to the first decibels, on the dBA scale), compared with the daytime, therefore - a loud, sharp noise with large jumps in volume can wake sleeping people.

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(SNiP3 "Protection against noise").

more death (noise weapon)

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The maximum permissible sound levels (LAmax, dBA) are 15 decibels more than "normal" ones. For example, for living rooms of apartments, the permissible constant sound level in the daytime is 40 decibels, and the temporary maximum is 55. With constantly operating engineering equipment, an amendment of minus 5 is taken into account.

Inaudible noise - sounds with frequencies less than Hz (infrasound) and more than 20 kHz (ultrasound). Low-frequency vibrations of 5-10 hertz can cause resonance, vibration of internal organs and affect the functioning of the brain. Low-frequency acoustic vibrations intensify aching pain in bones and joints in sick people. Sources of infrasound: cars, wagons, thunder from lightning, etc.

At workplaces the maximum permissible, by law, equivalent sound levels for intermittent noise: the maximum sound level should not exceed 110 dBA, and for impulse noise dBAI. Even a short stay in areas with sound pressure levels exceeding 135 dB in any octave band is prohibited.

For fire alarm: the sound pressure level of the useful audio signal provided by the siren must be at least 75 dBA at a distance of 3 m from the siren and not more than 120 dba at any point in the protected room (clause 3.14 of the airbag).

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A device is used to measure the noise level sound level meter (pictured), which is produced in different modifications: household (approximate price, measurement ranges: dB, 31.5 Hz - 8 kHz, filters A and C), industrial (integrating, etc.) The most common models: SL, octave, svan. For measurements of infrasonic and ultrasonic noises, wide-range noise meters are used.

Sound frequency ranges

mid-frequency 0 Hz;

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sand dry / wet0 /

They reduce the range of sound propagation, along the surface of the earth - high obstacles (mountains, buildings and structures), the opposite direction of the wind and its speed, as well as other factors (low atmospheric pressure, high temperature and humidity). Distances at which the source of loud noise is almost inaudible - usually, from 100 meters (in the presence of high obstacles or in a dense forest), house. - in an open area (with a favorable average wind - the range increases to a kilometer or more). With distance, higher frequencies are "lost" (they are damped and dissipated faster) and low-frequency sounds remain. The maximum propagation range of medium-intensity infrasound (a person does not hear it, but there is an effect on the body) is tens and hundreds of kilometers from the source.

The noisiest cities in Russia

These are many regional and district centers of the country, almost all territories of major transport hubs and urban residential buildings along avenues and near airports. This category includes: Moscow, St. Petersburg, Krasnoyarsk, Rostov-on-Don, Chelyabinsk, Yekaterinburg, Perm, Irkutsk, Yaroslavl, Voronezh, Novokuznetsk, Nizhny Tagil, Magnitogorsk, Omsk, Ufa, Samara, Nizhny Novgorod, Novosibirsk, Murmansk , Perm, Tula, Ulyanovsk, Kemerovo and others.

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When the right and left ears hear sounds (for example, from the headphones of the player, fhertz), the sounds decay, in perception, to the original ones, with their actual frequency, and the bin effect disappears. The phase difference of sound waves arriving at the right and left ear - allows you to determine the direction to the sound / noise source, volume and timbre - the distance to it.

International standardization of physical parameters

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A reaction to prolonged and strong noise exposure is "tinnitus" - ringing in the ears, "noise in the head", which can develop into progressive hearing loss. Typical for ages over 30, with a weakened body, stress, alcohol abuse and smoking. In the simplest case, ear noise or hearing loss can be caused by a wax plug in the ear, which can be easily removed by a specialist doctor (rinsing or removing). If the auditory nerve is inflamed, it can be cured, also relatively easily (with drugs, acupuncture). Pulsating noise is a more difficult case for treatment (possible causes: narrowing of blood vessels in atherosclerosis or tumors, as well as subluxation of the cervical vertebrae).

To protect your hearing:

In a noisy place, to protect your hearing - use anti-noise soft "earplugs", earbuds or earphones (noise reduction is more effective at high sound frequencies). They must be individually adjusted to fit the ear. In the field, they also use bulbs from a flashlight (they are not for everyone, but they are suitable in size). In shooting sports, individually cast "active earplugs" with electronic filling are used, for the price - like a telephone. Store them in packaging. It is better to choose bershhes made of hypoallergenic polymer with good SNR (noise reduction), at a level of 30 dB or more. In case of sudden changes in pressure (in an airplane), to equalize it and reduce pain, you need to use special pins with micro-holes;

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Techniques typically used to equalize the pressure on both sides of the ear drum: swallowing, yawning, blowing with closed nose. Frenzel's method - by pinching the nostrils, with an effort to pull the tongue back, along the palate (with muscle contraction, the nasal cavities and Eustachian tubes will open). Artillerymen, firing a shot, open their mouths or cover their ears with the palms of their hands.

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Sound level meter SL. Household and industrial sound level meters.

Noise level - what and how

In the parameters of climatic equipment, the noise level is indicated separately for the outdoor and indoor units. The noise of the indoor unit is caused by the sound of the air passing by the fan. Therefore, more expensive models of air conditioners, as a rule, have a larger size of the indoor unit compared to more budgetary models of the same capacity. The explanation is simple: a similar air volume passing through a larger fan rotating at a lower speed creates less noise.

Outdoor unit noise is primarily caused by compressor noise. Inverter air conditioners benefit greatly from this. Although the noise level of on / off air conditioners (not inverter) has also dropped significantly recently.

Note: The table is based on the manufacturers' data

From the point of view of the human ear, "noise" is a disorderly mixing of sounds that is unfavorable for human perception. The physical characteristic of sound loudness is the sound pressure level, in decibels (dB).

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A decibel is a dimensionless unit used to measure the ratio of certain quantities, in our case, the loudness of a sound. It is important to remember that this is not an absolute value, such as a watt or a volt, but the same relative value as a multiple ("threefold increase") or a percentage, intended to measure the ratio of two other quantities. In this case, in contrast to percent or multiplicity, a logarithmic scale is applied to the resulting ratio.

Decibels are widely used in the fields of technology where it is required to measure quantities varying in a wide range: in radio engineering, antenna technology, in information transmission systems, automatic regulation and control, in optics, acoustics, etc.

For a better understanding, consider two cases:

1. What happens if you increase the noise by 25 dB by another 25 dB? Noise with a total intensity of 50 dB? No - after all, when the number is doubled, its logarithm increases by

0.3 (accurate to two decimal places). Then, when the sound intensity is doubled, the intensity level increases by

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0.3 bela, that is, on

3dB, up to 28dB. This is true for any intensity level: doubling the sound intensity increases the intensity level by 3 dB.

2. How many times is the noise level of 20 and 32 dB different? If we were dealing with linear growth, then the answer would be simple: 32/20 \u003d

1.5 times. This is the mistake buyers make most often.

Note: Please note the difference between dB and dBA. dBA - acoustic decibel, a unit of measurement of the noise level, taking into account the perception of sound by humans. When measured in dBA, doubling the loudness roughly corresponds to a 10 dBA increase in noise level. Those. for 25 dBA an increase of 25 dBA

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Low and high pitched sounds seem quieter than midrange sounds of the same intensity.

A person, in the daytime, can hear sounds with a loudness of 10 - 15 dB and higher. The maximum frequency range for the human ear, on average from 20 to Hz (possible range of values: from 12 - 24 to – hertz). In youth, a mid-frequency sound with a frequency of 3 kHz is better heard, at an average age 2 - 3 kHz, in old age 1 kHz. Such frequencies, in the first kilohertz (up to 1000 - 3000 Hz speech communication zone) - are common in telephones. With age, the audible range of sounds narrows: for high-frequency sounds, it decreases to 18 kilohertz or less (in the elderly, every ten years by about 1000 Hz), and for low-frequency sounds it increases from 20 Hz or more.

For a sleeping person, the main source of information about the world around him is his ears. Hearing sensitivity sharply aggravates compared to the daytime, so noise that is imperceptible during the day, and especially noise with loudness jumps, can easily wake up sleeping people.

The absence of sound-absorbing materials (carpets, special coatings) on the walls of the premises, the sound will be louder due to multiple reflections (echoes) from walls, ceilings, furniture), which will increase the final noise level by several decibels.

Noise scale (sound levels in dBA - acoustic decibel, a unit of measurement of the noise level, taking into account human perception of sound)

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The permissible maximum according to the norms for residential premises at night, from 23 to 7 o'clock.

(SNiP3 "Protection against noise").

The norm for residential premises during the day, from 7 to 23 o'clock (SNiP3 "Protection against noise").

The maximum allowable sound pressure for the player's headphones.

At sound levels above 160 decibels, rupture of the eardrums and lungs is possible, more than 200 - death

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Spoken speech ranges from 45 decibels (dB) to 60 decibels (dB), depending on the volume of the voice;

The maximum permissible sound levels are 15 decibels higher than "normal". For example, for living rooms of apartments, the permissible constant sound level in the daytime is 40 decibels, and the temporary maximum is 55. With constantly operating engineering equipment, an amendment is taken into account: minus 5.

How and by what noise is measured

A sound level meter is used to measure the noise level. Sound level meters are household (measuring ranges 30 - 130 dB, 31.5 Hz - 8 kHz) and industrial. Wide-range sound level meters are used to measure infrasonic and ultrasonic noise.

One of the most important issues is the dependence of the sound level on its frequency. The lower frequency limit of human perception of sound is about 30 Hz, and the upper one is not higher than 18 kHz; therefore, the sound level meter would have to register sounds in the same frequency range. But here a serious difficulty arises. The fact is that the sensitivity of the human ear for different frequencies is not the same; So, for example, for sounds with a frequency of 30 Hz and 1 kHz to sound equally loud, the sound pressure level of the first of them should be 40 dB higher than the second. And therefore, the readings of the sound level meter alone are not worth much.

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Therefore, all modern sound level meters are equipped with correction circuits, thanks to which it is possible to reduce the sensitivity of the sound level meter to low-frequency and very high-frequency sounds and thereby bring the frequency characteristics of the device closer to the properties of the human ear. Usually the sound level meter contains three correction loops, designated A, B and C; correction A is most useful; correction B is used only occasionally; and even less often correction C.

Most often, the level of domestic and industrial noise is taken equal to the level measured in dB using a sound level meter with correction A, and expressed in units of dBA. Although the human ear perceives sound incomparably more subtly than the sound level meter, and therefore the sound levels expressed in dBA in no way correspond exactly to the physiological response, the simplicity of this unit makes it extremely convenient for practical use.

Another advantage of the dBA scale is the fact that doubling the volume roughly corresponds to an increase in the noise level by 10 dBA.

For an approximate assessment of the noise level, you can use "handy tools" in the form of a desktop computer, laptop, tablet and or smartphone. Of course, such a measurement will be rougher than that performed at least with the help of a household specialized sound level meter, but practically free of charge.

We measure the noise level using a desktop computer or laptop:

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For PCs with MS Windows 8, you can use the free Decibel Meter or Asa Tempo application. They can be downloaded from the Microsoft App Store (https://www.microsoft.com/en-us/store/apps/windows). These applications use a microphone connected to your computer, external or built-in, and can measure sounds up to 96 dB (Decibel Meter).
There are similar programs for Apple products in the iTunes App Store (Decibel 10th - Professional Noise Meter).
You can also use sound editors to measure noise volume. The main thing is that the program can work with a microphone as a sound source. For example, Audacity, a free sound editor (GNU GPL v2 license), has an input level metering function. It is available for a variety of operating systems: MS Windows (10/8/7 / Vista / XP), GNU / Linux, Mac OS X. You can download it from the developers website at http://www.audacityteam.org/ Users of the OS family GNU / Linux can in most cases install it directly from the repository of its distribution.

For tablet and smartphone:

A microphone in a mobile device will certainly not provide the same quality as an external microphone, but you will get the ability to measure the sound level almost anywhere. Nevertheless, this accuracy will be sufficient for estimating the noise level in most domestic cases.

For Apple devices: Decibel 10th, Decibel Meter Pro, dB Meter, Sound Level Meter;
For Android devices: deciBel, Decibel Meter, Noise Meter, Sound Meter;
For devices running MS Windows Phone: Cyberx Decibel Meter, Decibel Meter Free, Decibel Meter Pro.

What and how makes noise in the air conditioner

Compressor. It is also a source of low-frequency (including infra-low, propagating primarily along building structures) noise.

In split systems, its contribution is lower than in window or mobile models. Also in mobile and window systems, it is combined with the noise of the fan and the noise of the air flow.

2. Fan of the indoor unit. The motor should not be heard.

3. Swing sash. If you can hear it, contact the service

4. Relay for switching modes. Heard on non-inverter ("on / off") models

The noise of the refrigerant: it is heard along the lines only during heating, if it is heard during cooling, then there are some problems

What and how makes noise in heaters

In convectors (fan heaters) and heat guns: fans and air flow. The smaller the fan diameter, the greater the noise. The shape of the ventilation grill also affects the noise level.
In oil coolers - oil movement at high power
In gas and diesel heat guns: flame

Hygienic noise standards

To determine the permissible noise level at workplaces, in residential premises, public buildings and residential areas, GOST 12.1.003-83 is used. SSBT “Noise. General safety requirements ", CH 2.2.4 / 2.1.8." Noise at workplaces, in the premises of residential, public buildings and on the territory of residential buildings. " Normalization of noise in the audio range is carried out according to the limiting spectrum of the noise level and dBA. This method sets maximum permissible levels (MRLs) in nine octave bands with geometric mean frequencies of 31, 63, 125, 250, 500, 1000, 2000, 4000, 8000 Hz.

Noise at workplaces, in residential, public buildings and on the territory of residential buildings

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About decibels, Sound volume. Noise level and its sources

The physical characteristic of sound loudness is the sound pressure level, in decibels (dB). "Noise" is a disorderly mixture of sounds.

Low and high pitched sounds seem quieter than midrange sounds of the same intensity. Taking this into account, the uneven sensitivity of the human ear to sounds of different frequencies is modulated with the help of a special electronic frequency filter, obtaining, as a result of measurement normalization, the so-called equivalent (in energy, "weighted") sound level with the dimension dBA (dB (A), then yes - with filter "A").

A person, in the daytime, can hear sounds with a loudness of otb and higher. The maximum frequency range for the human ear, on average, is from 20 to Hz (possible range of values: from up to 00 Hz). In youth, a mid-frequency sound with a frequency of 3 KHz is better heard, in middle age - 2-3 KHz, in old age - 1 KHz. Such frequencies, in the first kilohertz (up to Hz - the zone of speech communication) - are common in telephones and on the radio on the MW and LW bands. With age, the audible range of sounds narrows: for high-frequency sounds - decreasing to 18 kilohertz or less (in older people, every ten years - by about 1000 Hz), and for low-frequency sounds - increasing from 20 Hz or more.

In a sleeping person, the main source of sensory information about the environment is the ears ("light sleep"). Hearing sensitivity, at night and with closed eyes, increases overB (up to the first decibels, on the dBA scale), compared with the daytime, therefore - loud, sharp noise with large jumps in volume can wake sleeping people.

In the absence of sound-absorbing materials (carpets, special coatings) on the walls of the premises, the sound will be louder due to multiple reflections (reverberation, that is, echoes from walls, ceilings and furniture), which will increase the noise level by several decibels.

Noise scale (sound levels, decibels), in the table

The permissible maximum according to the norms for residential premises at night, from 23 to 7 o'clock.

The norm for residential premises during the day, from 7 to 23 hours.

The maximum permissible sound pressure for the player's headphones (according to European standards)

At sound levels above 160 decibels, rupture of the eardrums and lungs is possible,

more death (noise weapon)

At workplaces, the maximum permissible, by law, equivalent sound levels for intermittent noise: the maximum sound level should not exceed 110 dBA, and for impulse noise dBAI. Even a short stay in areas with sound pressure levels exceeding 135 dB in any octave band is prohibited.

When erecting buildings and structures, in accordance with modern, more stringent sound insulation requirements, technologies and materials must be used that can provide reliable protection against noise.

116 dB (A) - when installing a sound emitter on the roof of a vehicle;

122 dBA - when installing the beam in the engine compartment of the vehicle.

The fundamental frequency changes should be between 150 and 2000 Hz. The cycle time is from 0.5 to 6.0 s.

If a city dweller, accustomed to constant noise, finds himself in complete silence for a while (in a dry cave, for example, where the noise level is less than 20 db), then he may well experience depression instead of rest.

The device is a noise meter for measuring the level of sound, noise

To measure the noise level, a sound level meter is used (in the photo), which is produced in different modifications: household (approximate price, measurement ranges: dB, 31.5 Hz - 8 kHz, filters A and C), industrial (integrating, etc.) The most common patterns are SL, octave, svan. Wide-range sound level meters are used to measure infrasonic and ultrasonic noise.

Sound frequency ranges

Sub-bands of the audio frequency spectrum, to which the filters of two- or three-band acoustic systems are tuned: low-frequency - oscillations up to 400 hertz;

mid-frequency 0 Hz;

Sound speed and range of its propagation

The approximate speed of audible, mid-frequency sound (with a frequency of about 1-2 kHz) and the maximum range of its propagation in various media:

in the air - 344.4 meters per second (at a temperature of 21.1 on the Celsius scale) and about 332 m / s - at zero degrees;

in water - about 1.5 kilometers per second;

in hardwood trees - about 4-5 km / s along the fibers and one and a half times less - across.

in stainless steel - 5.8 kilometers per second.

Polystyrene - 2.4 kilometers per second.

sand dry / wet0 /

They reduce the range of sound propagation, along the surface of the earth - high obstacles (mountains, buildings and structures), the opposite direction of the wind and its speed, as well as other factors (low atmospheric pressure, high temperature and humidity). Distances at which the source of loud noise is almost inaudible - usually, from 100 meters (in the presence of high obstacles or in a dense forest), house. - in an open area (with a favorable average wind - the range increases to a kilometer or more). With distance, the higher frequencies are “lost” (quickly damped and scattered) and low-frequency sounds remain. The maximum propagation range of medium-intensity infrasound (a person does not hear it, but there is an effect on the body) is tens and hundreds of kilometers from the source.

If during a thunderstorm you saw a strong lightning and after 12 seconds heard the first thunderclaps, this means that the lightning struck four kilometers from you (340 * 12 \u003d 4080 m.) In approximate calculations, it is assumed that three seconds per kilometer of distance (in the air space) to the sound source.

Binaural Beat Frequency

When the right and left ears hear sounds (for example, from the headphones of the player, f< 1000 герц, f1 - f2 < 25 Гц) двух различных частот - мозг, в результате обработки этих сигналов, получает третью, разностную частоту биения (бинауральный ритм, который равен арифметической разнице их частоты), «слышимую» как низкочастотные колебания, совпадающие с диапазоном обычных мозговых волн (дельта - до 4 Гц, тета - 4-8Гц, альфаГц, бетаГц). Этот биологический эффект учитывается и используется в студиях звукозаписи - для передачи низких частот, не воспроизводимых напрямую динамиками обычных стереосистем (вследствие конструкционных ограничений), но эти способы и методы, при неумелом применении, могут негативно сказаться на психологическом состоянии и настроении слушателя, так как отличаются от естественного, природного восприятия человеческим ухом шумов и звуков.

In those places of the ionosphere, where electromagnetic waves of sufficient power are beaten, with a stable (with a high quality factor of the signal) Schumann resonance, especially at the frequencies of its first harmonics, the plasma bunches that have appeared, at the same time, begin to emit infrasonic acoustic (sound) waves. Specific ionospheric emitters exist for as long as lightning strikes continue in the initiating thunderstorm center - approximately, up to the first tens of minutes. For the octahertz frequency, these radiating points are located on the opposite side of the globe, from the source of the electromagnet. waves. At 14 hertz - along the triangle. Local, highly ionized regions in the lower layers of the ionosphere (sporadic layer Es) and plasma reflectors - can be interconnected or spatially coincide.

Prolonged exposure to noise with a level of more than decibella can lead to partial or complete hearing loss (at concerts, the power of acoustic systems can reach tens of kilowatts). Also, this may cause pathological changes in the cardiovascular and nervous system. Only sounds with a volume of up to 35 dB are safe.

The reaction to prolonged and strong noise exposure is "tinnitus" - ringing in the ears, "noise in the head", which can develop into progressive hearing loss. Typical for ages over 30, with a weakened body, stress, alcohol abuse and smoking. In the simplest case, the cause of ear noise or hearing loss can be a cerumen plug in the ear, which can be easily removed by a specialist doctor (washing or extraction). If the auditory nerve is inflamed, it can be cured, also relatively easily (with drugs, acupuncture). Pulsating noise is a more difficult case for treatment (possible causes: narrowing of blood vessels in atherosclerosis or tumors, as well as subluxation of the cervical vertebrae).

To protect your hearing:

Do not increase the volume of the player's headphones trying to drown out external noise (in the subway or on the street). This also increases the electromagnetic radiation to the brain from the earpiece speaker;

In a noisy place, to protect the hearing organs - use anti-noise soft "earplugs", earbuds or headphones (noise reduction is more effective at high sound frequencies). They must be individually adjusted to fit the ear. In the field, they also use light bulbs from a flashlight (they are not for everyone, but they are suitable in size). In shooting sports, individually cast "active earplugs" with electronic filling are used, at a price like a telephone. Store them in packaging. It is better to choose bershees made from a hypoallergenic polymer that have good SNR (noise reduction), at a level of 30 dB or more. In case of sudden changes in pressure (in an airplane), to equalize it and reduce pain, you need to use special micro-holes;

Indoors, use noise-insulating environmentally friendly materials to reduce noise;

When diving, so as not to rupture the tympanic membrane - blow out in time (blow out the ears by pinching the nose or swallowing). Immediately after diving - not on a plane. Jumping with a parachute - you also need to equalize the pressure in a timely manner so as not to get barotrauma. Consequences of barotrauma: noise and ringing in the ears (subjective "tinnitus"), hearing loss, ear pain, nausea and dizziness, in severe cases - loss of consciousness.

With a cold and a runny nose, when the nose and maxillary sinuses are stuffy, sudden pressure drops are unacceptable: diving (hydrostatic pressure - 1 atmosphere per 10 meters of immersion depth in water, that is: two - at ten, three - at around 20 m. And etc.), parachute jumps (0.01 atm. per 100 m. height, rapidly increasing, with acceleration).

// about seven and a half millimeters of mercury of the barometer - for every hundred meters, in height.

Give your ears a break from loud noise.

Techniques usually used to equalize the pressure on both sides of the eardrum: swallowing, yawning, blowing with a closed nose. Artillerymen, firing a shot, open their mouths or cover their ears with the palms of their hands.

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Noise level. What does 35 dB mean and what it can be compared to

The noise characteristics of the equipment are given in the form of tables, which contain:

Noise sound power level LWA in dB (A) by frequency band, sound power levels to the input, to the output and to the fan environment.
General sound pressure level dB (A) at a distance of 3m.

The frequency band is divided into 8 wave groups. In each group, the average frequency is determined: 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2 kHz, 4 kHz and 8 kHz. Any noise is decomposed into groups of frequencies and you can find the distribution of sound energy at different frequencies.

The noise from the fan spreads through the air duct (air duct), partially attenuates in its elements, and through the air distribution and air intake grilles penetrates into the served room.

The basis for the design of ventilation systems is acoustic calculation - a mandatory application to the ventilation project of any object.

The main tasks of such a calculation: determination of the octave spectrum of ventilation noise at design points and its required reduction by comparing this spectrum with the permissible spectrum according to hygienic standards. After the selection of construction and acoustic measures to ensure the required noise reduction, a verification calculation of the expected sound pressure levels at the same design points is carried out, taking into account the effectiveness of these measures.

i can not hear anything

almost inaudible

quiet rustle of leaves

whisper of a person (at a distance of 1m).

whisper of a man (1m)

the whisper, the ticking of the wall clock.

the norm for residential premises at night, from 23 to 7 in the morning

norm for residential premises, from 7 to 23 hours

normal conversation

conversation, typewriter

Standard for class A office premises (according to European standards)

office norm

loud conversation (at a distance of 1m)

loud conversations (1m)

scream, motorcycle sound with muffler

loud scream, muffled motorcycle sound

loud shouts, freight railroad car (at a distance of 7 m)

sound of a passing subway car (7m)

the sound of an orchestra, intermittent sounds of a passing subway car, thunderclaps

the maximum permissible sound pressure for the player's headphones (according to European standards)

The physical characteristic of sound loudness is the sound pressure level, in decibels (dB). "Noise" is a disorderly mixture of sounds.

A person, in the daytime, can hear sounds with a volume of 10-15 dB and higher. The maximum frequency range for the human ear, on average, is from 20 to 20,000 Hz (possible range of values: from 12-24 to 18,000-24,000 hertz). In youth, a mid-frequency sound with a frequency of 3 KHz is better heard, in middle age - 2-3 KHz, in old age - 1 KHz. Such frequencies, in the first kilohertz (up to 1000-3000 Hz - the zone of speech communication) - are common in telephones and on the radio on the MW and LW bands. With age, the audible range of sounds narrows: for high-frequency sounds - decreasing to 18 kilohertz or less (in older people, every ten years - by about 1000 Hz), and for low-frequency sounds - increasing from 20 Hz or more.

In a sleeping person, the ears become the main source of sensory information about the environment ("light sleep"). Hearing sensitivity, at night and with closed eyes, increases by 10-14 dB (up to the first decibels, on the dBA scale), compared to the daytime, therefore - loud, sharp noise with large jumps in volume can wake sleeping people.

Noise scale (sound levels, decibels), in the table

Decibel, dBA	Characteristic	Sound sources
0	I can not hear anything
5	Almost inaudible
10	Almost inaudible	quiet rustle of leaves
15	Barely audible	rustle of foliage
20	Barely audible	whisper of a person (at a distance of 1 meter).
25	Quiet	whisper of a man (1m)
30	Quiet	the whisper, the ticking of the wall clock. The permissible maximum according to the norms for residential premises at night, from 23 to 7 hours.
35	Quite audible	muffled conversation
40	Quite audible	ordinary speech. The norm for residential premises during the day, from 7 to 23 hours.
45	Quite audible	normal conversation
50	Clearly audible	conversation, typewriter
55	Clearly audible	Upper norm for class A office space (according to European standards)
60	Noisy	Norm for offices
65	Noisy	loud talk (1m)
70	Noisy	loud conversations (1m)
75	Noisy	scream, laugh (1m)
80	Very noisy	scream, motorcycle with a silencer.
85	Very noisy	loud scream, muffled motorcycle
90	Very noisy	loud screams, freight railroad car (seven meters)
95	Very noisy	subway car (7 meters outside or inside the carriage)
100	Extremely noisy	orchestra, subway car (intermittently), thunderclaps The maximum permissible sound pressure for the player's headphones (according to European standards)
105	Extremely noisy	in an airplane (until the 80s of the twentieth century)
110	Extremely noisy	helicopter
115	Extremely noisy	sandblasting machine (1m)
120	Almost unbearable	jackhammer (1m)
125	Almost unbearable
130	Pain threshold	the plane at the start
135	Contusion
140	Contusion	the sound of a jet taking off
145	Contusion	rocket launch
150	Contusion, trauma
155	Contusion, trauma
160	Shock, trauma	shock wave from a supersonic aircraft
At sound levels above 160 decibels, rupture of the eardrums and lungs is possible, more than 200 - death (noise weapon)

Inaudible noise - sounds with frequencies less than 16-20 Hz (infrasound) and more than 20 kHz (ultrasound). Low-frequency vibrations of 5-10 hertz can cause resonance, vibration of internal organs and affect the functioning of the brain. Low-frequency acoustic vibrations intensify aching pain in bones and joints in sick people. Sources of infrasound: cars, wagons, thunder from lightning, etc.

High-frequency sound and ultrasound with a frequency of 20-50 kilohertz, reproduced with a modulation of several hertz, are used to scare away birds from airfields, animals (dogs, for example) and insects (mosquitoes, midges).

At workplaces, the legal maximum permissible equivalent sound levels for intermittent noise: the maximum sound level should not exceed 110 dBA, and for impulse noise - 125 dBAI. Even a short stay in areas with sound pressure levels exceeding 135 dB in any octave band is prohibited.

The noise emitted by a computer, printer and fax in a room without sound absorbing materials - may exceed 70 db. Therefore, it is not recommended to place a lot of office equipment in one room. Equipment that is too noisy should be removed outside the premises where the workplaces are located. You can reduce the noise level if you use noise-absorbing materials as decoration of the room and curtains made of thick fabric. Anti-noise earbuds will also help.

Crying a child, in comparison with other sounds of the same volume, has a much stronger effect on the human psyche, as an irritant and stimulus for active physical actions (to calm down, feed, etc.)

Siren of high power and ship's howler - pressures more than 120-130 decibels.

Special signals (sirens and "crackers" - Air Horn) installed on service vehicles are regulated by GOST R 50574 - 2002. Sound pressure level of the signaling device when a special sound is applied. signal, at a distance of 2 meters along the horn axis, must be at least:
116 dB (A) - when installing a sound emitter on the roof of a vehicle;
122 dBA - when installing the beam in the engine compartment of the vehicle.
The fundamental frequency changes should be between 150 and 2000 Hz. The cycle time is from 0.5 to 6.0 s.

The horn of a civil car, according to GOST R 41.28-99 and UNECE Regulation No. 28, must emit a continuous and monotonous sound with an acoustic pressure level of no more than 118 decibels. This order is the maximum permissible values \u200b\u200b- and for car alarms.

The device is a noise meter for measuring the level of sound, noise

To measure the noise level, a sound level meter is used (pictured), which is produced in different modifications: household (approximate price - 3-4 tr, measurement ranges: 30-130 dB, 31.5 Hz - 8 kHz, filters A and C ), industrial (integrating, etc.) The most common models: SL, octave, svan. Wide-range sound level meters are used to measure infrasonic and ultrasonic noise.

Sound frequency ranges

Sub-bands of the audio frequency spectrum, to which the filters of two- or three-band acoustic systems are tuned: low-frequency - oscillations up to 400 hertz;
mid-frequency - 400-5000 Hz;
high-frequency - 5000-20000Hz

Sound speed and range of its propagation

The approximate speed of audible, mid-frequency sound (with a frequency of about 1-2 kHz) and the maximum range of its propagation in various media:
in the air - 344.4 meters per second (at a temperature of 21.1 on the Celsius scale) and about 332 m / s - at zero degrees;
in water - about 1.5 kilometers per second;
in hardwood trees - about 4-5 km / s along the fibers and one and a half times less - across.

At 20 ° C., The speed of sound in fresh water is 1484 m / s (at 17 ° - 1430), in sea water - 1490 m / s.

The speed of sound in metals and other solids (only the values \u200b\u200bof the fastest, longitudinal elastic waves are given):
in stainless steel - 5.8 kilometers per second.
Cast iron - 4.5
Ice - 3-4km / s
Copper - 4.7 km / s
Aluminum - 6.3km / s
Polystyrene - 2.4 kilometers per second.

With increasing temperature and pressure, the speed of sound in air increases. In liquids, the temperature is inverse.

Velocity of propagation of elastic longitudinal waves in rock mass, m / s:
soil - 200-800
dry / wet sand - 300-1000 / 700-1300
clay - 1800-2400
limestone - 3200-5500

They reduce the range of sound propagation, along the surface of the earth - high obstacles (mountains, buildings and structures), the opposite direction of the wind and its speed, as well as other factors (low atmospheric pressure, high temperature and humidity). Distances at which the source of loud noise is almost inaudible - usually, from 100 meters (in the presence of high obstacles or in a dense forest), to 300-800 m. - in an open area (with a favorable average wind, the range increases to a kilometer or more) ... With distance, higher frequencies are "lost" (more quickly attenuated and scattered) and low-frequency sounds remain. The maximum propagation range of medium-intensity infrasound (a person does not hear it, but there is an effect on the body) is tens and hundreds of kilometers from the source.

The attenuation intensity (absorption coefficient) of mid-frequency sound (about 1-8 kHz), at normal atmospheric pressure and temperature, above the ground with low grass, in the steppe is approximately 10-20 dB for every 100 meters. The absorption is proportional to the square of the acoustic frequency.

The line of propagation of sound waves deviates in the direction of decreasing the speed of sound (refraction on the temperature gradient), that is, on a sunny day, when the air at the surface of the earth is warmer than the overlying one - the line of propagation of sound waves bends upward, but if the upper layer of the atmosphere turns out to be warmer than the surface layer, then the sound will go back down from there and it will be heard better.

Diffraction of sound - wave bending around an obstacle when its size is comparable to the wavelength or less. If much longer than the wavelength, then the sound is reflected (the angle of reflection is equal to the angle of incidence), and an acoustic shadow zone is formed behind the obstacles.

Reflections of a sound wave, its refraction and diffraction - cause multiple echoes (reverberation), which has a significant effect on the audibility of speech and music in the room or outside, which is taken into account when recording, to obtain a live sound (by placing small-sized microphones with a sharp directivity characteristic, for recording direct sound, followed by mixing and mixing "dry" recording by the processor into digital or using long-equidistant, well-tuned surround microphones with additional recording of reflected sounds).

Conventional sound insulation does not save from infrasound.

Binaural Beat Frequency

When the right and left ears hear sounds (for example, from the headphones of the player, f< 1000 герц, f1 - f2 < 25 Гц) двух различных частот - мозг, в результате обработки этих сигналов, получает третью, разностную частоту биения (бинауральный ритм, который равен арифметической разнице их частоты), "слышимую" как низкочастотные колебания, совпадающие с диапазоном обычных мозговых волн (дельта - до 4 Гц, тета - 4-8Гц, альфа - 8-13Гц, бета - 13-30 Гц). Этот биологический эффект учитывается и используется в студиях звукозаписи - для передачи низких частот, не воспроизводимых напрямую динамиками обычных стереосистем (вследствие конструкционных ограничений), но эти способы и методы, при неумелом применении, могут негативно сказаться на психологическом состоянии и настроении слушателя, так как отличаются от естественного, природного восприятия человеческим ухом шумов и звуков.

// with the binaural effect, not three, but two sounds are "audible": the first is the arithmetic mean, in frequency, from two real ones, and the second is the clock, modeled by the brain. With an increase in the frequency difference (\u003e 20-30 hertz), the sounds decay, in perception, into the original ones, with their actual frequency, and the bin effect disappears. The phase difference of sound waves arriving at the right and left ear - allows you to determine the direction to the sound / noise source, volume and timbre - the distance to it.

Schumann resonance

How to keep your hearing

Prolonged exposure to noise levels of more than 80-90 decibels can lead to partial or complete hearing loss (at concerts, the power of acoustic systems can reach tens of kilowatts). Also, this may cause pathological changes in the cardiovascular and nervous system. Only sounds with a volume of up to 35 dB are safe.

To protect your hearing:

Do not increase the volume of the player's headphones, trying to drown out external noise (in the subway or on the street). This also increases the electromagnetic radiation to the brain from the earpiece speaker;
... in a noisy place, to protect the hearing organs - use anti-noise soft "earplugs", earbuds or earphones (noise reduction is more effective at high sound frequencies). They must be individually adjusted to fit the ear. In the field, they also use light bulbs from a flashlight (they are not for everyone, but they are suitable in size). In shooting sports, individually cast "active earplugs" with electronic filling are used, at a price like a telephone. Store them in packaging. It is better to choose bershs made of hypoallergenic polymer with good SNR (noise reduction), at a level of 30 dB or more. In case of sudden changes in pressure (in an airplane), to equalize it and reduce pain, you need to use special pins with micro-holes;
... use noise-insulating environmentally friendly materials in the premises to reduce noise;
... when diving, so as not to rupture the tympanic membrane - to purge in time (to purge the ears by pinching the nose or swallowing). Immediately after diving - not on a plane. Jumping with a parachute - you also need to equalize the pressure in a timely manner so as not to get barotrauma. Consequences of barotrauma: noise and ringing in the ears (subjective "tinnitus"), hearing loss, ear pain, nausea and dizziness, in severe cases - loss of consciousness.
... with a cold and runny nose, when the nose and maxillary sinuses are stuffed up, sudden pressure drops are unacceptable: diving (hydrostatic pressure - 1 atmosphere per 10 meters of immersion depth in water, that is: two - at ten, three - at 20 m and etc.), parachute jumps (0.01 atm. per 100 m. height, rapidly increasing, with acceleration).
// about seven and a half millimeters of mercury of the barometer - for every hundred meters, in height.
... rest your ears from loud noise.

Techniques usually used to equalize the pressure on both sides of the eardrum of the ear: swallowing, yawning, blowing with a closed nose. The gunners, firing a shot, open their mouths or cover their ears with the palms of their hands.

Common causes of hearing loss: water ingress into the ears, infections (including the respiratory system), trauma and swelling, the formation of a sulfur plug and its swelling upon contact with water, prolonged stay in a noisy environment, barotrauma with a sharp drop in pressure, inflammation of the middle ear - otitis media (accumulation of fluid behind the eardrum).

Noise is defined as an irregular combination of different sounds with tones of varying strength and frequency. Noise levels are to be measured in quantities capable of expressing the degree of sound pressure produced. Such units of measurement of noise level are associated with the names of two physicists - Alexander Bell and Heinrich Hertz.

Belami, and more often decibels, is the relative loudness of the sound. At its core, a decibel is ten times the logarithm of the ratio of the intensity of existing sound energy to its value. It is not directly a unit of measurement, but an expression of a relationship.

The measurable characteristic of sound is the amount of energy it contains. That is, its intensity as a flow of this energy. That is why the quantitative characteristic is, for example, the expression in watts per square meter (W / m2). However, the values \u200b\u200bobtained with respect to the reference level of 10-12 W / m2 are so small and incomprehensible to most ordinary people that 1 bel was "adopted" to express the resulting relations. For example, the noise level of a jet aircraft is on the order of 13 bels or, in smaller values, 130 decibels (dB). For the human ear, the normal noise range is 20 to 120 decibels. Sounds above this level can cause serious injury to the eardrum and contusion. And 160 dB can be fatal.

All people are faced with household noise. They consist of those that arise directly in the room and penetrate from the outside. In order to protect the health and the normal state of citizens, the norms of permissible penetrating noise have been adopted. This is 40 dB during the day and 30 at night. The average indicators of noise measurement units prove that in about 80% of cases, even with normal operation of radio and TV, conversations, noise coming from neighboring apartments is kept at a level of 40-45 dB, and sounds from the entrance (elevator movement, door slamming) reach 60 dB.

In addition to the intensity of sound, the human ear is sensitive to noise vibrations. Hertz is a unit C of frequency, equal to the frequency of the ongoing periodic process, in which one cycle of such a periodic process occurs in 1 second (that is, 1 oscillation). Therefore, for an objective characterization, it is necessary to use both of these units of measurement of the noise level. The human hearing aid is more sensitive to vibrations generated by high frequencies than by low frequencies. But in industrial and living conditions, everyone is under the influence of the entire spectrum. In this regard, when comparing the level of sound loudness, it is necessary, in addition to the characteristics of the strength and intensity of sound in decibels, to indicate the frequency of vibrations per second.

At the household level, noise is a sound that does not carry useful information. Although for any of us, utility is a relative concept. For a taxi passenger, incomprehensible sounds under the hood may be just noise, but they signal to the driver about a possible malfunction of the car. Let's define what noise is and learn as much as possible about this physical phenomenon.

What is noise?

For any physicist, noise is an oscillatory process. It can be portrayed on paper as an alternation of density waves: condensation waves change places with rarefaction waves. This process is possible only in an elastic medium: sound vibrations in a vacuum, for example, do not propagate. If the bodies vibrate out of order, the human hearing perceives these sounds as noise.

Noise parameters

All sounds have their own unique set of parameters, thanks to which we can identify them. Sound vibrations can be measured by:

the strength of sound, which is directly dependent on the pressure that the sound wave produces;
frequency of sound. The higher the vibration frequency, the higher the sound we hear.

For sound in general and for noise in particular, scientists have created their own measurement parameter - "bel". This unit was named after Alexander Bell, the famous inventor of telephone communications.

Hearing and noise

To the human ear, all noise sources are in the 45 to 11,000 Hz range. If you use a musical term, then the whole variety of sounds (including noise) entered into nine octave bands.

Our hearing organs are not able to distinguish to distinguish the entire range of sound vibrations - it is too large. But evolution provides for an instinctive reaction not to the noise itself, but to its change. That is why the human ear has learned to distinguish the frequency of changes in the sound wave.

In order to classify noise adequately and scientifically, the change in sound pressure is expressed in logarithmic units. This way it is much more convenient to depict sound processes graphically. The commonly used unit of measurement for noise is decibel, which is one tenth of a white. The range of sound pressure changes from the threshold of hearing to painful sensations caused by noise is millions of dB.

Types of noise

For technical descriptions, all noise can be separated by temporal and spectral parameters. By the nature of the spectral bands, noise is distinguished:

broadband (the width of the continuous spectrum exceeds the width of an octave);
tonal (excess of noise in one third octave band in comparison with the others by more than 10 dB).

Noise classification can also be based on time characteristics. Constant noise changes its frequency by no more than 5 dBA. Unstable sound vibrations have a greater amplitude of changes and are subdivided into:

fluctuating - continuous changes over time;
intermittent - changes occur stepwise, there are intervals of constant noise of one or more seconds;
impulse - alternating noise and silence

Measurement of the noise level is measured with special devices - sound level meters.

How the sound level meter works

The device for measuring noise has a fairly simple device: a voltmeter calibrated in decibels and electrical filters are connected to a small microphone. The sound signal is perceived by the microphone and translated into an electrical impulse equal in strength and frequency to the original wave. The increase in the electric field is recorded by a voltmeter and displayed on the display. According to its characteristics, the device for measuring noise should be “on the same sound wave” with the human hearing. This simple device serves as a reliable indicator of noise pollution in a home or work environment.

Noise Sources and Comparative Noise Levels

The modern technological world contains many sources of noise. These are: various types of transport, sounds of any devices or equipment, sound equipment, and so on.

All the sounds we hear during the day merge into a cacophony, which we perceive as noise. At home, the noise is several times less than at work (even if your neighbor is a fan of indigestible loud sounds, which he calls songs). Industrial sources today are the main culprits "of noise pollution of the earth. Among the main "villains" are the metallurgical, mining, coal, petrochemical and defense industries. Food industry workers hear the least sounds.

Some technological processes in production, for example, at enterprises producing reinforced concrete structures, test ranges or shooting ranges, cosmodromes, can be sources of noise reaching up to 120 dBA.

The permissible noise level is determined by the standards GOST 12.1.003-83. SSBT. The standardization of noise pollution is carried out according to the permissible spectrum of noise levels and dBa. This method helps to establish the maximum permissible noise level in nine octave bands.

What are the noises

Scientists could not ignore the whole variety of sound stimuli and came up with various classifications of what noise is. Physics studies these sound phenomena and classifies them for ease of study. We have already got acquainted with some types of noise earlier. Here are a few more options for ranking various sound phenomena by their nature of occurrence:

mechanical - sounds that occur during the operation of various mechanisms;
aerodynamic. This includes the noise generated by the aircraft taking off;
hydraulic. We hear these noises in case of malfunctions in the native water supply system: a sudden pressure drop in the system can cause a water hammer, which is perceived as a sharp, unpleasant noise;
electromagnetic. Occur during the operation of devices and devices of the same name.

A separate category is the "color" noise classification. So, "white" noise of technology is called a stationary sound stream, in which the spectral components are uniformly distributed over the entire range. The rest of the technical noises are classified as colored. This analogy arose when comparing the spectrum of sound waves with the spectral bands of visible light. Thus, “pink” noise is often present in the heart rate, in space radiation, in electronic or mechanical devices. The "orange" noise corresponds to the frequencies of the musical notes. “Red Noise” is the melody of various natural bodies of water on Earth. Well, "green" noises are emitted by all green plants of our planet.

Noises around us

Every day, all people who are able to distinguish between sounds are faced with different types of sound vibrations. Offhand, you can determine the strength of the sound emitted by various sources of noise that surround us in everyday life.

Normal conversation: 40-45 dB.
Noise of work in the office, doctor's office, lawyer: 50-60 dB.
Street sounds: the voices of passers-by, traffic flows: 70-80 dB.
Noise at the factory (tyazhprom): 70-110 dB.
Start of a modern airliner: 120 dB.
Maximum vuvuzela volume: 130 dB.

The human body quickly adapts to noise. Suffice it to say that the sound background that has become familiar to us, our ancestors would have regarded as an intolerable sound cacophony. But the human body is not able to withstand constant noise load. Noises in the audio range dull a person's response to external signals. This leads to a decrease in the speed of adequate response and an increase in errors when performing certain types of work.

Noise is the cause of central nervous system depression. A constant stream of sound causes noticeable changes in the rate of pulse and respiration, disrupts metabolism. Noise exposure leads to a variety of cardiovascular diseases, hypertension and stomach ulcers. When exposed to "high" noises with a volume higher than 140 dB, contusion and rupture of the tympanic membrane are possible. Noise above 160 dB causes fatal cerebral hemorrhage.

Noise and nature

Noise pollution is dangerous not only for humans. Scientific research confirms that the powerful engines of modern ships and submarines disorient aquatic creatures who use sonar to find food and communicate. Dolphins and some species of cetaceans especially suffer from constant fluctuations in the sound background of the ocean. It is possible that reliable but unexplained cases of collective suicide of whales are somehow related to a violation of their orientation skills. In a number of cases, the mass throwing of whales ashore was recorded near the places where military exercises were held, which means that the noise pollution in this region was extremely high.

Noise and space

As mentioned earlier, noise cannot occur in an inelastic environment. And the cosmic vacuum is the most inelastic medium of all possible. However, in 2006, NASA researchers discovered an effect later called "cosmic noise." Of course, the discovered effect is not noise in the usual sense of the word. This was the name of the mysterious radio waves that penetrate the entire space of the universe. Their frequency, strength and amplitude of oscillation coincided so much with the known sources of sounds that scientists did not hesitate to record radio waves into the category of noise.

Cosmic noise is radio waves emitted by stars billions of light-years distant from us. Supernova explosions, turbulence of gas nebulae and so on can become alternative sources of the noise phenomenon. Any cosmic process is accompanied by the release of radio waves into a vacuum, which can be studied and classified. Thanks to the phenomenon of cosmic noise, we can learn how stars were formed and what fate, in the end, awaits our Universe.

In fact, to measure the noise level you need a microphone and a special analyzer program. A laptop, tablet, or smartphone has a microphone. You can connect an external microphone to your desktop computer. It remains to download the analyzer program.

Noise level can be measured on a computer using the free Decibel Reader software. Also sound level meters are in many recording programs. For example, Audacity.

On a smartphone or tablet, the microphone is generally inferior to the external microphone connected to the computer. But even with it, you can carry out a fairly accurate measurement of the noise level. Calibration with professional instruments shows that the measurement accuracy on a smartphone can differ from professional equipment by only 5 decibels. So even specialists in noise diagnostics use mobile applications for operational work.

- one of the applications with sound level meter function. Note that measurements are not in dBA, but in dB.

A “normal” decibel is dB, a unit of sound pressure. But our ear perceives the pressure of sounds of different frequencies in different ways. In order for the sound level meter to show the real noise level that a person hears, it must have a so-called frequency filter A. With it, dB turns into that very dBA.

There is no frequency filter in Smart Tools, but you can get a general idea of \u200b\u200bthe noise level without it.

Other Noise Measurement Applications:

MacOS: Decibel 10th, Decibel Meter Pro, dB Meter, Sound Level Meter
Android: Sound Meter, Decibel Meter, Noise Meter, deciBel
Windows: Decibel Meter Free, Cyberx Decibel Meter, Decibel Meter Pro

An important point:

in specialized sound level meters (even the simplest ones), the parameters of the microphone and signal processor are matched. A smartphone does not have this, so the measurement accuracy of a mobile application will always be lower than with a special device.