In physics, sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the reception of such waves and their perception by the brain. Humans can only hear sound waves as distinct pitches when the frequency lies between about 20 Hz and 20 kHz. Sound waves above 20 kHz are known as ultrasound and is not perceptible by humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges.

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  1. ATCclears

    Sound travels slower (and at variable speeds) on Mars
  2. ilikegunspdx

    Some 22lr sound levels with suppressor test results

    FYI did some testing with some various guns and same suppressor, same location, same dirt target. Sound was measured approx 5 feet away to the shooter's immediate left (the side opposite from the ejection port). Used federal suppressor 45grain 970fps. Was shot under an overhang structure so...
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