A student is standing 8 m from a roaring truck engine that is measured at 20 db. The student moves 4 m closer to the engine. What is the measured sound intensity at the new distance?

The answer to the question above is explained below

Explanation:

The loudness or sound intensity of the roaring truck engine is inversely proportional to the square of the distance.

r1^2 / r2^2 = L2/L1

Where, r1 and r2 = old distance and new distance respectively,

L1 and L2 = old sound intensity and new sound intensity respectively.

From the parameters given above,

r1=8m

r2=4m

L2=?

L1 = 20dB

8^2 / 4^2 = L2 / 20 dB

L2 = 80 dB

The answer is 80 dB. Increased from 20 dB.

Decibel (dB), is a relative unit of measurement used for expressing the ratio between two physical quantities, usually electric power, or for measuring Sound intensity. Decibels measure the ratio of a given intensity to the threshold of hearing intensity.

Sound intensity, also known as acoustic intensity, is a vector describing the intensity of a sound is proportional to its amplitude squared.

80 dB

Explanation:

Sound intensity is inversely proportional to the square of the distance traveled by the sound.

Thus;

r1^2 divide by r2^2 = L2divideL1

where r = distance (m)

L = sound intensity (decibal dB)

8squared divide by 4 squared = L2 divide 20 dB

L2 = 4 * 20

L2 = 80 dB

This means that the sound is increased from 20 dB to 80 dB.