Don's Home Technology Sound Sound - Loudness Contact

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See also:
Sound Frequency | Sound Loudness

Audio - stereo - Home Theater (Surround Sound) in home and garden.
Frequency Response Specs
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What is Sound

Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium (air, water, wook, ...) through which the sound wave is moving.
There are regions in the air where the air particles are compressed together (compressions) and other regions where the air particles are spread apart (rarefactions). The compressions are regions of high air pressure while the rarefactions are regions of low air pressure.
The greater the difference between the high air pressure and low air pressure is the loudness.
Sound waves are sometimes represented by a pressure graf.
They may look like ocean waves with an up and down motion, but they do not move up and down. The graph represents pressure not distance.
The differences between the high and low pressure is loudness. A big difference or the higher the graph is a loud sound.
The distance between the waves are represents frequency. Close = high frequency, spread out = low frequency.
How closely they are packed together represents volume.
 

Sound loudness measurement

The greater the difference between the high air pressure and low air pressure is the loudness.
Sound waves are sometimes represented by a pressure graf.
They may look like ocean waves with an up and down motion, but they do not move up and down. The graph represents pressure not distance.
The differences between the high and low pressure is loudness. A big difference or the higher the graph is a loud sound.

The unit measure of SPL (Sound Pressure Level) is decibels (dB). It is measured with a Sound Pressure Level Meter.

Sound is a mechanical (not electrical) wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving.

Loudness is measured in decibels (dB). A decibel is one tenth of a bel, a seldom-used unit named in honor of Alexander Graham Bell.
It is a logarithmic (base 10) scale so 20 dB has 100 times the power as 10 dB. 30 dB has 1,000 times.
Human senses, nearly all, work in a manner and obey Weber–Fechner law , that response of the sense machinery in the brain is logarithm of an input.

A-weighted decibels, abbreviated dBA, or dBa, or dB(a), are an expression of the relative loudness of sounds in air as perceived by the human ear.
The human ear is more sensitive to sound in the frequency range 1 kHz to 4 kHz than to sound at very low or high frequencies. dBa adjusts sound level down at low and high frequencies to compensate for this.
See: Decibel A, B and C at EngineeringToolbox.com
Sounds with a loudness of 120 dB or more can cause pain and damage to the human ear.

A pascal (Pa) is the SI-derived unit of sound pressure. It is a measure of force per unit area, defined as one newton per square meter. Examples are
You will also see presure as W/m2 watts per meter squared.
a trumpet at 1 m distance: 40 Pa or 126 dB
normal conversation at 1 m distance: 6 mPa (millipascal or mPA = 1/1,000 Pa) or 50 dB Hearing threshold — 0 dB Whisper at 1 m distance — 20 dB Quiet conversation at 1 m distance — 50 dB Threshold of pain — 130 dB Concert (Any genre) - 110 dB Jet takeoff (200 ft) - 120 dB Convert pascal [Pa] to sound pressure level in decibels [dB SPL] Sound pressure (p) is the average variation in atmospheric pressure caused by the sound. The unit of pressure measurement is pascal (Pa). Sound pressure level (SPL) is the pressure level of a sound, measured in decibels (dB). It is equal to 20 x the Log10 of the ratio of the Route Mean Square (RMS) of sound pressure to the reference of sound pressure (the reference sound pressure in air is 2 x 10-5 N/m2, or 0,00002 Pa). Or, in other words is the ratio of the absolute sound pressure against a reference level of sound in the air. Sound Pressure Level (SPL) Converter • Acoustics — Sound • Unit definitions • Online Unit Converters https://www.translatorscafe.com/unit-converter/en-US/sound-pressure-level/definitions/

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A-weighted decibels, abbreviated dBA, or dBa, or dB(a), are an expression of the relative loudness of sounds in air as perceived by the human ear.
The human ear is more sensitive to sound in the frequency range 1 kHz to 4 kHz than to sound at very low or high frequencies. dBa adjusts sound level down at low and high frequencies to compensate for this.
See: Decibel A, B and C at EngineeringToolbox.com
Sounds with a loudness of 120 dB or more can cause pain and damage to the human ear.

LOUDNESS OF SOME SOUNDS

Sound Decibels (dB)
jet engine 170
rock concert 100-125
thunderstorm 90-110
vacuum cleaner 75-80
conversation 60-70
refrigerator 40
classroom 35
whispering 10-20
near total silence 0
See:
Acceptable Noise - dBA - Levels

The speed of a sound wave depends upon the medium the wave is moving through. Sound moves faster through dense materials such as wood or metal because the molecules are close together. Sound also moves faster through warmer materials because the molecules of a warm substance are colliding more often than the molecules of a cold substance.

Medium Speed of Sound (m/sec)
air (0° C./32° F.)
(sea level)
331 (740 MPH)
air (20° C./68° F.) 344 (770 MPH)
cork 500
alcohol 1,240
water 1,500
wood (oak) 3,850
brick 3,650
glass 4,540
aluminum 5,000
iron 5,103
steel 5,200
I've seen Mach 1 (the speed of sound) listed as 761.5 and 770 MPH.

last updated 17 Mar 2022