The decibel scale is referenced to a standard intensity of?

Question

A) 1.0W/m^2
B)10^-12W/m^2
C)normal conversation
D) the threshold of pain

Answer 1

Sound level measurements in decibels are generally referenced to a standard threshold of hearing at 1000 Hz for the human ear which can be stated in terms of sound intensity.

B is the correct answer. 10^-12W/m^2

But the decibel can be used for things other than sound. The bel, from Graham Bell, is the logarithmic ratio between the input and output of any given component, circuit, or system. The bel maybe expressed in voltage, current, sound levels, or power. The formula is: The gain of an amplifier can be expressed in bels (N) by dividing the output (P1) by the input (P2) and taking the base 10 logarithm (log 10) of the resulting quotient.

N = log(P1/P2) bel

For sound the P2 is the threshold of hearing. But suppose you have an amplifier that doubles the power, the quotient will be 2. When you consult a log table, you will find that the base 10 log of 2 is 0.3; so the power gain of the amplifier is 0.3 bel. But the bel is a rather large unit that is difficult to apply. A more practical unit to is the decibel (1/10 bel). To convert from bels to decibels just multiply the value by 10. The 0.3 bel is then equal to 3 decibels.

Answer 2

The decibel scale is referenced to a standard intensity of
*****************************************************
1 watt at 1 meter away from source
+db gain=10*log(p2/p1)

a,b,c,d are all wrong the way that u wrote them out

Answer 3

decibels measure pressure, ie sound, and normal conversation is the only answer that has anything to do with sound.