What is Decibel?
| Electrical Power Levels Or Sound-Wave Intensities |
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A unit of measurement that can be used to compare electrical power levels or sound-wave intensities. One-tenth of a bel. It is equal to 10 times the logarithm of the power ratio, 20 times the log of the voltage ratio, or 20 times the log of the current ratio. One decibel is the amount by which the pressure of a pure sine wave of sound must be varied in order for the change to be detected by the average human ear. The decibel can express an actual level only when comparing with some definite reference level that is assumed to zero dB. For example, back-ground noise in an office might be about 70dB; safety regulations suggest an exposure limit of 90dB unless special protection is worn. In computing terms, you may see the noise produced by a printer quoted by the manufacturer in dB(A) - a figure calculated (or adjusted) from the measured dBs to give a more accurate representation of how the noise sounds to the human ear. It's very important to remember when comparing dB levels that for every extra 3dB of noise the sound intensity doubles, so a printer producing 63dB(A) is making twice the noise of one producing 60dB(A). |
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