Technical Pages - Audio
The Basics
Acoustics - This is the 'physics of how sound works'
The Decibel - (dB) This is most commonly used in audio terminology to describe (SPL's) Sound Pressure Levels although it can also be used to express audio levels and level differences in SPL's, Power, Voltages and current.
The Bel is defined as the logarithm of a power ratio:
Bel = P1 / P0
|
Decibels |
Example |
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|
Threshold of Pain |
140 |
Jet Engine (75ft away) |
Painful & Dangerous |
|
130 |
Jet Aircraft during take off (300ft away) |
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|
Threshold of Feeling |
120 |
Hard Rock Band (with amplification) |
Deafening |
|
110 |
Accelerating Motorcycle at a few feet away. |
||
|
100 |
Car Horn at 10ft / Footbal Crowd / Printing Press |
Very Loud |
|
|
90 |
Pneumatic Concrete Breaker |
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|
Threshold of hearing loss |
80 |
Café with sound reflecting surfaces |
Loud |
|
(long term exposure) |
70 |
B-757 Aircraft cabin during flight Crackling of food wrapper (2ft away) |
|
|
60 |
Near Road Traffic (when greater than 55dB road & rail annoy most people) |
Moderate |
|
|
Speech 50-70dB |
50 |
Office Environment |
|
|
40 |
Soft Stereo Music at home |
Faint |
|
|
30 |
Home environment without stereo, late at night |
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|
20 |
Whisper / Audiometric testing room |
Very Faint |
|
|
10 |
Russle of leaves in breeze / Human breathing |
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|
Threshold of hearing |
0 |
Efficiency - When comparing loudspeakers it is useful to have a reference point of how efficient the loudspeaker is at converting the electrical power supplied to them into acoustical power.
Watts
Wavelength, Frequency & Velocity