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- A sound pressure expressed in dB above the standard sound pressure of 20 µPa.
The following reference pressures are in common use: (a) 2 X 10E-4
microbar, (b) 1 microbar. Reference pressure (a) is in general use for
measurements concerned with hearing and with sound in air and liquids,
whereas (b) has gained widespread acceptance for calibration of
transducers and various kinds of sound measurements in liquids. Unless
otherwise explicitly stated, it is to be understood that the sound
pressure is the effective (root-mean-square) sound pressure. It is to be
noted that in many sound fields the sound pressure ratios are not the
square roots of the corresponding power ratios.
- The power level of sound being the sound pressure squared, referenced to 20
mPa2 measured in dB. Commonly, how loud the sound is measured in decibels.
Speech is around 70-80 dB at three feet. Normal background noise on average is
50-60dB. 120dB is the threshold of pain. 200dB is 50lbs of TNT detonated 10
feet away.
Source:
Church Audio & Acoustics Glossary
- Ten times the logarithm of the ratio of the
time-mean-square pressure of a sound, in a stated frequency band or with a
stated frequency weighting, to the square of the reference sound pressure of 20
micropascal. Unit, decibel (dB); symbol, L{sub p}.
Source:
Glossary of Terms
in Noise Control Engineering
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(abbreviated SPL): Ten times the base-10 logarithm of the time-mean-square
sound pressure, in a stated frequency band (often frequency-weighted), divided
by the squared reference sound pressure of 20 • Pa,
the threshold of human hearing.
SPL = 10 × log10[p2÷pref2]
Where
p2 = time-mean-square
sound pressure; and
pref2 =
squared reference sound pressure of 20 • Pa.
Source:
http://www.volpe.dot.gov/acoustics/docs/1990-1999/1999-1.pdf
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Given in decibels (dB) is an expression of loudness or volume. A 10 dB increase
in SPL represents a doubling in volume. Live orchestral music reaches brief
peaks in the 105 dB range and live rock easily goes over 120 dB.
Source:
http://www.owenscorning.com/around/sound/glossary.asp
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