Quality of a sound

Quality of  a sound

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Introduction : In previous topic we have discussed about the factors affecting the velocity of a sound. In this topic we are going to discuss which parameter helps in understanding the quality of sound. We are going to discuss more about quality of sound in this topic.

Quality of the sound depends upon major three factors.

a) Pitch :  Pitch relates to the sharpness or shrillness of a sound . If the sharpness of the sound is more then sound is said to be highly pitched. The more the frequency ,more is the pitch. For eg. The difference heard in the voice of a women and men is due to difference in pitch. Voice of female is very sharp i,e they have high pitch whereas the voice of men is having low pitch i.e low frequency.

b) Timber : Timber refers to quality of a sound heard by a listener .We are able to guess the difference between the voice when the person is suffering from cold or cough. The quality of sound in a musical instruments are due to mixture of tones and overtones. The sound quality in this context mentioned  is called as Timbre.

c) Loudness : Loudness of any sound depends on the intensity of a sound. Intensity  of a sound is defined as Sound energy passing through a given a area per unit time.

I = E / At

I = P/A

Where 

I = Intensity

P = Power

A = Area

SI unit of Intensity is Watt / m²

The maximum intensity that any human ear can hear  is I_max = 10¹ Watt / m²

The minimum intensity that any human ear can hear  is I₀ = 10^-12 Watt / m²

Mathematical expression for Loudness of a sound

According to weber fechner,

The loudness (L) of a sound is directly proportional to  ( log₁₀ I )

For maximum Loudness,

L_max ∝  log₁₀ (I_max)  -----(1)

For maximum Loudness,

L₀ ∝  log₁₀ (I₀) -----(2)

From (1) and (2) subtracting

L_max - L₀   ∝  log₁₀ (I_max)  -  log₁₀ (I₀) 

L_max - L₀   = K  log₁₀ (I_max)  -  log₁₀ (I₀) 

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