Question

Human hearing is directly sensitive to sound pressure which is related to sound intensity. Determine the S.I. unit of intensity of sound.
a. Joule ${s^{ - 1}}{m^{ - 2}}$
b. Watt ${m^{ - 2}}$
c. Joule $s{m^{ - 2}}$
d. Both A and B

Answer 1

Hint: The intensity of sound is the power of sound in watts divided by the area the sound covers in square meters. It is also defined as the power carried by sound waves per unit area in a direction perpendicular to that area.

Complete steps by step solution :
We know that Sound Intensity is the product of the sound pressure and the particle velocity flowing through a specified area.

Therefore according to definition,
Intensity of sound = $\dfrac{{Power}}{{Area}}$

We know that
S.I. unit of power is watt as well joule ${s^{ - 1}}$

S.I. unit of area is ${m^2}$

$\therefore $S.I. Unit of intensity of sound = $\dfrac{{watt}}{{{m^2}}}$= watt ${m^{ - 2}}$

$\therefore $S.I. Unit of intensity of sound = $\dfrac{{joule}}{{s{m^2}}}$= joule ${s^{ - 1}}{m^{ - 2}}$

Hence the correct option is D.

Note: The intensity of sound can be also defined as the work done per second in order to cross a unit area. There are various units of intensity depending upon the types of unit conversion.