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Name: Jenna T.
Status: other
Age: 20s
Location: N/A
Country: N/A
Date: 2001-2002


Question:
What is a decibel and what is the difference between dB and dBA? Also can you give comparison's in sound to say 5 dBA and 10dBA? Also what is an Ohms reader?


Replies:
A decibel is a measure of sound loudness -- the square of the compressional pressure. IT IS A LOGARITHMIC SCALE. There are two weighting scales for measuring the loudness. The "C" scale has a flat sensitivity from 32 to 10,000 hertz. Above 10,000 hertz the sensitivity falls off rather rapidly due to the physical limitations of the microphones above that frequency. The "C" weighting is assigned a response of 0 dB across its range of sensitivity (This is arbitrary). The "A" scale is weighted to approximate the typical sensitivity of the human ear (Obviously, this is an average population). Between 1000 and 10,000 hertz the sensitivity of the two scales is essentially the same. At 500 hertz the "A" scale is about -10 dB; at 100 hertz the "A"scale is about -25 dB; at 50 hertz the "A" scale is about -40 dB, and at 20 hertz the "A" scale is about -50dB.

One dB is approximately the faintest sound audible to the human ear; background music is about 50 dB; heavy rock music is about 110dB; pain threshold is about 125 dB.

Vince Calder



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