Powersound (relative) is an obsolete term describing a quantity like sound intensity but not identical to it. We observe approximately the same situation for forces of light(unit - candela) is a quantity similar to radiation strength(unit - watt on the steradian).
Sound power is measured by relative scale from the threshold value, which corresponds to sound intensity 1 pW / m² at a sinusoidal frequency of 1 kHz and sound pressure 20 μPa. Compare this definition with the definition of the unit of luminous intensity: “ candela is equal to the intensity of light emitted in a given direction by a monochromatic source, at a radiation frequency of 540 THz and a radiation intensity in this direction of 1/683 W / sr ".
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Sound volume- subjective perception strength sound(the absolute value of the auditory sensation). The volume mainly depends on sound pressure, amplitudes and frequency sound vibrations. Also, the loudness of the sound is influenced by its frequency, spectral composition, localization in space, timbre, duration of exposure to sound vibrations and other factors (see. , ).
The unit of the absolute loudness scale is dream ... Volume in 1 sleep is the volume of a continuous pure sine tone with a frequency of 1 kHz creating sound pressure 2 MPa.
Sound volume level- relative value. It is expressed in backdrops and is numerically equal to the level sound pressure(v decibels- dB) generated by a sinusoidal tone with a frequency of 1 kHz the same loudness as the sound being measured (equal to the loudness of the given sound).
Dependence of the volume level on sound pressure and frequency
The figure on the right shows a family of equal loudness curves, also called isophones... They are graphs of standardized (international standard ISO 226) dependences of sound pressure level on frequency at a given volume level. Using this diagram, you can determine the loudness level of a pure tone of any frequency, knowing the level of sound pressure it creates.
sound surveillance equipment
For example, if a sine wave with a frequency of 100 Hz creates a sound pressure of 60 dB, then by drawing straight lines corresponding to these values on the diagram, we find at their intersection an isophone corresponding to a loudness level of 50 phon. This means that this sound has a volume level of 50 phon.
Isophone "0 background", indicated by a dotted line, characterizes hearing threshold sounds of different frequencies for normal hearing.
In practice, it is often not the loudness level expressed in backgrounds that is of interest, but the value that shows how much a given sound is louder than another. Also of interest is the question of how the volumes of two different tones add up. So, if there are two tones of different frequencies with a level of 70 phon each, this does not mean that the total volume level will be 140 phon.
Loudness versus sound pressure level (and sound intensity) is a purely nonlinear curve, it has a logarithmic character. With an increase in the sound pressure level by 10 dB (i.e. 10 times), the sound volume will increase 2 times. This means that volume levels of 40, 50 and 60 phon correspond to volumes of 1, 2 and 4 sones.
Noises are created sound waves arising from expansion and contraction in air and other media. In air conditioning and ventilation systems, noise can arise and spread in the air, air duct housings, fluids moving through pipes, etc.Noises can have different frequencies and intensities.
Sound propagation speed
Noise travels at a much slower speed than light waves. The speed of sound in air is approximately 330 m / s. In liquids and solids, the speed of propagation of noise is higher; it depends on the density and structure of the substance.Example: the speed of sound in water is 1.4 km / s, and in steel - 4.9 km / s.
Noise frequency
The main noise parameter is its frequency(number of vibrations per second). The unit of measurement for frequency is 1 hertz (Hz), which equals 1 sound wave vibration per second.Human hearing picks up frequency fluctuations from 20 Hz to 20,000 Hz. During the operation of air conditioning systems, the frequency spectrum from 60 to 4000 Hz is usually taken into account.
For physical calculations, the audible frequency band is divided into 8 wave groups. In each group, the average frequency is determined: 62 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.
Sound power
Sound power of any installation - this is the energy that is released by the installation in the form of noise per unit of time. It is inconvenient to measure the strength of the noise in standard power units, because the spectrum of sound frequencies is very wide, and the power of sounds differs by many orders of magnitude.Example: the power of noise when air enters a room under low pressure is equal to one hundred billion watt, and when a jet plane is taking off, the noise power reaches 1000 W.
Therefore, the sound power level is measured in logarithmic units - decibels (dB). In decibels, the strength of the noise is expressed in two- or three-digit numbers, which is convenient for calculations.
The sound power level in dB is a function of the ratio of the power of sound waves near the noise source to the zero value W 0, equal to 10 -12 W. The power level is calculated using the formula:
L w = 10lg (W / W0)
Example: if the sound power near the source is 10 W, then the power level is 130 dB, and if the sound power is 0.001 W, then the power level is 90 dB.
Sound power and power level are independent of the distance to the noise source. They are related only to the parameters and operating mode of the installation, therefore, they are important for the design and comparison of various air conditioning and ventilation systems.
The power level cannot be measured directly, it is determined indirectly by special equipment.
Sound pressure level
Pressure level sound L p is the perceived intensity of the noise, measured in dB.L p = P / P0
Here P is the sound pressure at the measured place, μPa, and P 0= 2 μPa - reference value.
The sound pressure level depends on external factors: distance from the installation, sound reflection, etc. The simplest form is the dependence of the pressure level on the distance. If the noise power level is known L w, then the sound pressure level L p in dB at a distance r (in meters) from the source is calculated as follows:
L p = L w - lgr - 11
Example: The sound power of the refrigeration unit is 78 dB. The sound pressure level at a distance of 10 m from it is: (78 - lg10 - 11) dB = 66 dB.
If the sound pressure level is known L p1 on distance r1 from the noise source, the sound pressure level L p2 on distance r2 will be calculated like this:
L p2 = L p1 - 20 * log (r2 / r1)
Example: The sound pressure level at a distance of 1 m from the unit is 65 dB. Then the sound pressure level at a distance of 10 m from it is: (65 - 20 * lg10) dB = (65 - 20) dB = 45 dB ..
In general, in an open space, the sound pressure level decreases by 6 dB when the distance to the noise source increases by 2 times. In a room, dependence will be more difficult due to the absorption of sound by the floor surface, sound reflection, etc.
Noise volume
Human sensitivity to sounds of different frequencies is not the same. It is maximum for sounds with a frequency of about 4 kHz, is stable in the range from 200 to 2000 Hz, and decreases at a frequency of less than 200 Hz (low-frequency sounds).The volume of the noise depends on the strength of the sound and its frequency. The loudness of the sound is estimated by comparing it with the loudness of a simple sound signal with a frequency of 1000 Hz. The level of sound intensity at 1000Hz, as loud as the noise being measured, is called the loudness level of that noise. The diagram below shows sound intensity versus frequency at constant volume.
At a low volume level, a person is less sensitive to sounds of very low and high frequencies. At high sound pressure, the sensation of sound develops into a painful sensation. At a frequency of 1 kHz, the pain threshold corresponds to a pressure of 20 Pa and a sound power of 10 W / m2.
Equal loudness curve diagram
Noise characteristics of equipment
The noise characteristics of the equipment are presented in the form of tables, which contain:- noise power level in dB by frequency bands
- general sound pressure level
Summation of noise sources
The noise from multiple sources does not correspond to the sum of the noise from each source separately. For two installations adjacent to each other, the noise is determined as follows:- If the noise level indicators are the same, then the total noise level is 3 dB higher than the noise level of each installation.
- If the difference in noise levels exceeds 10 dB, the total noise level is equal to the larger of the two noises.
For example, the total noise from two installations with levels of 30 and 60 dB is 60 dB.
- If the difference in noise levels is not more than 10 dB, use the table below. We calculate the difference in noise levels of installations.
If there are more than two noise sources, the calculation method does not change, and the sources are considered in pairs, starting with the weakest.
For example, there are four settings with noise levels of 25 dB, 38 dB, 43 dB and 50 dB.
First, we calculate for the two weakest settings: 38 - 25 = 13 dB. The difference is more than 10 dB, and this setting is not taken into account at all.
For 38 and 43 dB settings: 43 - 38 = 5 dB, the correction from the table is 1.2 dB. The total noise of the three settings: 43 + 1.2 = 44.2 dB.
Now let's find the total noise of all installations. 50 - 44.2 = 5.8 dB. Rounding off the difference in noise levels to 6 dB, we find a correction of 1.0 dB from the table.
So, the total noise level of the four installations is 50 + 1 = 51 dB.
Sound waves, affecting the human eardrum, cause hairs to vibrate. The amplitude of these is directly related to the perceived loudness of these waves - the higher it is, the stronger the sound will be felt. This is, of course, a simplified interpretation. But the point is clear!
The perception of the same sound power will be different for each person. Therefore, it would be fair to say that loudness is a subjective value. In addition, this parameter depends on the frequency and amplitude of sound vibrations, as well as the pressure of the waves. The sound volume is influenced by such factors as the duration of the oscillations, their localization in space, timbre and spectral composition.
The unit is called sone. 1 dream roughly corresponds to the volume of a muffled conversation, and the volume of the aircraft engines is 264 son. By definition, 1 dream is equal to the loudness of a tone with a frequency of 1000 and a level of 40 dB. The power of sound, expressed in sones, has the formula:
J = k * I 1/3, here
k - frequency-dependent coefficient, i - vibration intensity.
Due to the fact that vibrations with different (differing in their intensity) at different frequencies can have the same sound loudness, a unit such as background (phon) is also used to assess its strength. 1 Ф is equal to the difference in loudness levels of 2 sounds with the same frequency, for which the same loudness of 1000 Hz will differ in pressure (intensity) level by 1 decibel.
In practice, in order to indicate or compare loudness, the decibel is most often used - a unit derived from bel. This is due to the fact that the increase in the strength of sound occurs not in a linear dependence on the intensity of the waves, but in a logarithmic one. 1 bel is equal to a tenfold change in the strength of the amplitude of the oscillations. This is a fairly large unit. Therefore, for calculations, use its tenth part - decibel.
During the day, the human ear can hear sound waves with a volume of 10 decibels and above. It is generally accepted that the maximum range of all frequencies available to humans is 20-20,000 Hz. It is noticed that it changes with age. In youth, mid-frequency waves (about 3 kHz) are best heard, in adulthood - frequencies from 2 to 3 kHz, and in old age - sound at 1 kHz. Sound waves with an amplitude of up to 1-3 kHz (first kilohertz) enter the speech communication zone. They are used in radio broadcasting on the DV and MW bands, as well as in telephones.
If the frequency is less than 16-20 Hz, then such noise is considered as infrasound, and if it is more than 20 KHz - as ultrasound. Infrasound with fluctuations of 5-10 Hz can cause resonance with vibration of internal organs, affect the work of the brain and intensify aching pain in joints and bones. But ultrasound has found wide application in medicine. It also scares away insects (midges, mosquitoes), animals (for example, dogs), birds from airfields.
To find out the loudness of a sound or noise, a special device is used - a meter. It helps to find out whether the sound vibrations exceed the maximum permissible value, which does not pose a danger to humans. If a person is exposed to waves with a level exceeding 80-90 dB for a long time, it can cause complete or partial hearing loss. In this case, pathological disorders in the nervous and cardiovascular systems can also occur. The safe volume is limited to 35 dB. Therefore, to preserve your hearing, you should not listen to music at full volume with headphones. If you are in an area that is too noisy, you can use earplugs.
In this article, you will learn what sound is, what its lethal volume is, and its speed in air and other environments. We'll also talk about frequency, encoding and sound quality.
Let's also look at sampling, formats and sound power. But first, let's define music as an ordered sound - the opposite of a disordered chaotic sound that we perceive as noise.
- these are sound waves that are formed as a result of vibrations and changes in the atmosphere, as well as objects around us.
Even during a conversation, you hear your interlocutor because he affects the air. Also, when you play a musical instrument, whether you hit a drum or pluck a string, you are producing vibrations of a certain frequency, which produces sound waves in the surrounding air.
Sound waves are ordered and chaotic... When they are ordered and periodic (repeated after a certain period of time), we hear a certain frequency or pitch.
That is, we can define the frequency as the number of repetitions of an event in a given period of time. Thus, when sound waves are chaotic, we perceive them as noise.
But when the waves are ordered and periodically repeated, then we can measure them by the number of repeating cycles per second.
Audio sampling rate
The audio sampling rate is the number of measurements of the signal level in 1 second. Hertz (Hz) or Hertz (Hz) is a scientific unit of measurement that determines the number of times an event repeats per second. We will use this unit!
Audio sampling rate You have probably seen such an abbreviation very often - Hz or Hz. For example, in equalizer plugins. In them, the units of measurement are hertz and kilohertz (that is, 1000 Hz).
Typically, a person hears sound waves from 20 Hz to 20,000 Hz (or 20 kHz). Anything less than 20 Hz is infrasound... Anything over 20 kHz is ultrasound.
Let me open the EQ plugin and show you what it looks like. You are probably familiar with these numbers.
Sound frequencies With the equalizer, you can attenuate or boost certain frequencies within the human-audible range.
A small example!
Here I have a recording of a sound wave that was generated at 1000 Hz (or 1 kHz). If we zoom in and look at its shape, we will see that it is correct and repetitive (periodic).
Repetitive (periodic) sound wave In one second, a thousand repeating cycles occur here. For comparison, let's look at a sound wave, which we perceive as noise.
Disordered sound There is no specific repetitive frequency. There is also no specific tone or pitch. The sound wave is out of order. If we look at the shape of this wave, we can see that there is nothing repetitive or periodic in it.
Let's move on to the more saturated part of the wave. We zoom in and see that it is not constant.
Disordered wave when scaling Due to the lack of cyclicality, we are not able to hear any specific frequency in this wave. Therefore, we perceive it as noise.
Deadly sound level
I want to mention a little about the lethal sound level for humans. It originates from 180 dB and higher.
It should be said right away that according to regulatory standards, a safe noise level is considered to be no more than 55 dB (decibel) during the day and 40 dB at night. Even with prolonged exposure to hearing, this level is not harmful.
| Sound volume levels | ||
|---|---|---|
| (dB) | Definition | A source |
| 0 | Not fluffy at all | |
| 5 | Almost inaudible | |
| 10 | Almost inaudible | Quiet rustle of leaves |
| 15 | Barely audible | Rustle of foliage |
| 20 — 25 | Barely audible | Whispers of a man at a distance of 1 meter |
| 30 | Quiet | The ticking of the wall clock ( permissible maximum according to the norms for residential premises at night from 23 to 7 o'clock) |
| 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 | Talk |
| 50 | Clearly audible | Typewriter |
| 55 | Clearly audible | Talk ( European norm for class A office premises) |
| 60 | (office norm) | |
| 65 | Loud talk (1m) | |
| 70 | Loud conversations (1m) | |
| 75 | Scream and laugh (1m) | |
| 80 | Very noisy | Scream, a motorcycle with a muffler |
| 85 | Very noisy | Loud scream, muffled motorcycle |
| 90 | Very noisy | Loud screams, freight railroad car (7m) |
| 95 | Very noisy | Metro carriage (7 meters outside or inside the carriage) |
| 100 | Extremely noisy | Orchestra, thunder ( according to European standards, this is the maximum permissible sound pressure for headphones) |
| 105 | Extremely noisy | In old planes |
| 110 | Extremely noisy | Helicopter |
| 115 | Extremely noisy | Sandblasting machine (1m) |
| 120-125 | Almost unbearable | Jackhammer |
| 130 | Pain threshold | Airplane at the start |
| 135 — 140 | Contusion | Taking off jet plane |
| 145 | Contusion | Rocket launch |
| 150 — 155 | Contusion, trauma | |
| 160 | Shock, trauma | Shock wave from a supersonic aircraft |
| 165+ | Ruptured eardrums and lungs | |
| 180+ | Death | |
Sound speed in km per hour and meters per second
The speed of sound is the speed at which waves travel through the medium. Below I give a table of the propagation rates in various environments.
The speed of sound in air is much lower than in solid media. And the speed of sound in water is much higher than in air. It is 1430 m / s. As a result, the spread is faster and the audibility is much farther.
Sound power is the energy that is transmitted by a sound wave through the surface of interest per unit of time. Measured in (W). There is an instantaneous value and an average (over a period of time).
Let's continue working with the definitions from the music theory section!
Pitch and note
Height Is a musical term that means almost the same as frequency. The exception is that it has no unit of measurement. Instead of defining sound by the number of cycles per second in the range of 20 - 20,000 Hz, we denote certain frequency values in Latin letters.
Musical instruments produce periodic sound waves of regular shapes, which we call tones or notes.
That is, in other words, it is a kind of snapshot of a periodic sound wave of a certain frequency. The pitch of this note tells us how high or low the note sounds. In this case, lower notes have longer waves. And the tall ones are shorter.
Let's take a look at a 1 kHz sound wave. Now I will zoom in and you will see what the distance between the cycles is.
Sound wave at 1 kHz Now let's take a look at the 500 Hz waveform. Here the frequency is 2 times less and the distance between cycles is greater.
Sound wave at 500 Hz Now let's take a waveform of 80 Hz. Here it will be even wider and much lower.
Sound at 80 Hz We see the relationship between pitch and waveform.
Each musical note is based on one fundamental frequency (pitch). But in addition to tone in music, it also consists of additional resonant frequencies or overtones.
Let me show you another example!
Below is a 440 Hz wave. It is the world's standard for tuning instruments. It corresponds to the note a.
Pure sound wave at 440 Hz We only hear the fundamental tone (pure sound wave). If we zoom in, we will see that it is periodic.
Now let's look at a wave of the same frequency played on the piano.
Periodic piano sound Look, it is also periodic. But it has small additions and nuances. All of these together give us an idea of how a piano sounds. But in addition, overtones also cause the fact that some notes will have a greater affinity for a given note than others.
For example, you can play the same note, but one octave higher. The sound will be completely different. However, it will be akin to the previous note. That is, it is the same note, only played an octave higher.
This kindred relationship between two notes in different octaves is due to the presence of overtones. They are constantly present and determine how closely or distantly certain notes are related to each other.
The unit of the absolute loudness scale is background... The volume in 1 phon is the loudness of a continuous pure sinusoidal tone with a frequency of 1 kHz, creating a sound pressure of 2 MPa.
Sound volume level- relative value. It is expressed in backdrops and is numerically equal to the sound pressure level (in decibels - dB) created by a sinusoidal tone with a frequency of 1 kHz of the same loudness as the sound being measured (equal to the given sound).
Dependence of the volume level on sound pressure and frequency
The figure on the right shows a family of equal loudness curves, also called isophones... They are graphs of standardized (international standard ISO 226) the dependences of the sound pressure level on frequency at a given volume level. Using this diagram, you can determine the loudness level of a pure tone of any frequency, knowing the level of sound pressure it creates.
Sound surveillance equipment
For example, if a sine wave with a frequency of 100 Hz creates a sound pressure of 60 dB, then by drawing straight lines corresponding to these values on the diagram, we find at their intersection an isophone corresponding to a loudness level of 50 phon. This means that this sound has a volume level of 50 phon.
Isophone "0 background", indicated by a dotted line, characterizes hearing threshold sounds of different frequencies for normal hearing.
In practice, it is often not the loudness level expressed in backgrounds that is of interest, but the value that shows how much a given sound is louder than another. Also of interest is the question of how the volumes of two different tones add up. So, if there are two tones of different frequencies with a level of 70 phon each, this does not mean that the total volume level will be 140 phon.
The dependence of loudness on the sound pressure level (and sound intensity) is a purely non-linear curve, it has a logarithmic character. With an increase in the sound pressure level by 10 dB, the sound volume will double. This means that volume levels of 40, 50 and 60 phon correspond to volumes of 1, 2 and 4 sones.
| Sound | Volume, sones: |
Volume level, backgrounds: |
|---|---|---|
| Hearing threshold | 0 | 0 |
| The ticking of a wristwatch | ~ 0.02 | 10 |
| Whisper | ~ 0.15 | 20 |
| Wall clock sound | ~ 0.4 | 30 |
| Muffled conversation | ~ 1 | 40 |
| Quiet street | ~ 2 | 50 |
| Normal conversation | ~ 4 | 60 |
| Noisy street | ~ 8 | 70 |
| Level hazardous to health | ~ 10 | 75 |
| Pneumatic hammer | ~ 32 | 90 |
| Blacksmith shop | ~ 64 | 100 |
| Loud music | ~ 128 | 110 |
| Pain threshold | ~ 256 | 120 |
| Siren | ~ 512 | 130 |
| Reactive plane | ~ 2048 | 150 |
| Deadly level | ~ 16384 | 180 |
| Noise weapon | ~ 65536 | 200 |
Notes (edit)
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See what "Sound volume" is in other dictionaries:
A quantity that characterizes the auditory sensation for a given sound. G. z. complexly depends on sound pressure (or sound intensity), frequency and mode of vibration. At constant frequency and form of G.'s oscillations z. the sound grows with increasing ... ... Physical encyclopedia
The magnitude of the auditory sensation, depending on the intensity of the sound and its frequency. At a constant frequency, the volume of the sound rises with increasing intensity. At the same intensity, the loudest sounds are in the frequency range 700-6000 ... ... Big Encyclopedic Dictionary
sound volume- The magnitude of the auditory sensation, depending on the intensity of sound and its frequency [Terminological dictionary for construction in 12 languages (VNIIIS Gosstroy USSR)] Topics noise, sound EN sound loudnesssound volume DE Lautstärke FR intensité de sonvolume ... ... Technical translator's guide
The magnitude of the auditory sensation, depending on the intensity of the sound and its frequency. At a constant frequency, the volume of the sound increases with increasing intensity. At the same intensity, the loudest sounds are in the frequency range of 700 ... ... encyclopedic Dictionary
A measure of the strength of the auditory sensation caused by sound. G. z. depends on the effective sound pressure and sound frequency (see fig.). For comparison G. z. use the value LN, to paradise called. G.'s level z. and is equal to: LN = 20 lg (p * eff / p * 0), where p * 0 = 20 ... ... Big Encyclopedic Polytechnic Dictionary
sound volume- garsumas statusas T sritis radioelektronika atitikmenys: angl. volume of sound vok. Lautheit, f; Lautstärke, f; Tonstärke, f rus. sound volume, f pranc. volume sonore, m ... Radioelektronikos terminų žodynas
A quantity that characterizes the auditory sensation for a given sound. G. z. complexly depends on sound pressure (see Sound pressure) (or sound intensity (see Sound intensity)), frequency and mode. With unchanged ... ... Great Soviet Encyclopedia
sound volume- rus intensity (g) (strength) of sound, loudness (g) of sound eng sound intensity fra intensité (f) acoustique, intensité (f) sonore, intensité (f) du son deu Schallintensität (f), Schallstärke (f) spa intensidad (f) sonora, intensidad (f) acústica ... Occupational safety and health. Translation into English, French, German, Spanish
The magnitude of the auditory sensation, depending on the intensity of the sound and its frequency. At unchanged G.'s frequency z. grows with increasing intensity. At the same intensity naib. sounds in the frequency range of 700-6000 Hz have a loudness. Zero ... ... Natural science. encyclopedic Dictionary
The magnitude of the auditory sensation, depending on the intensity of the sound and its frequency (Bulgarian; Български) sound strength (Czech; Čeština) hlasitost zvuku (German; Deutsch) Lautstärke (Hungarian; Magyar) hangosság (Mongolian ... ... Construction vocabulary
Books
- A set of tables. Physics. Mechanical waves. Acoustics (8 tables),. Educational album of 8 sheets. Article - 5-8665-008. Wave process. Longitudinal waves. Transverse waves. Periodic waves. Reflection of waves. Standing waves. Sound waves. The pitch. ...
