Question

Unit of loudness is
(A). Phon
(B). Bol
(C). Both
(D). None

Answer 1

Sound has many different properties which enable us to distinguish between different sounds, one such property is loudness. Loudness is the measure of intensity of a sound, and it is calculated by the amplitude. It is measured on many different scales. Very loud sounds can be harmful to the ear.

Complete answer:
Loudness is one of the properties of sound. It depends on the amplitude. The higher the amplitude of sound the louder it is and vice versa. Loudness is the property of sound which determines the intensity of the sound produced. Therefore, the loudness of sound, as perceived by an average human ear is directly proportional to the logarithm of sound intensity.
The SI unit of sound is phon. Phon is defined as the number of decibels of a sound whose frequency is 1000 Hertz.
There are different scales which are used to judge the loudness of a sound. For example- decibel scale. The decibel scale is an objective scale while the phon scale is a subjective scale, this means that the judgement of the listener plays an important role in determining the loudness.
Therefore, loudness is measured by the amplitude and its SI unit is phon.

Hence, the correct option is (A).

Note:
The other scale used to judge the loudness of a sound is stone. Amplitude is defined as the maximum displacement travelled by a body about its mean position. Number of oscillations completed in one second is called frequency. An average person can only hear frequencies between 20 hertz to 20,000 hertz.