Explain the characteristics of sound. On what factors do they depend?

Characteristics of sound. The three characteristics of sound are (i) Loudness, (ii) Pitch and (iii) Quality or timbre.

(i) Loudness. Loudness is the physiological response of the ear to the intensity of sound. It distinguishes between a loud sound and low sound. Even when two sounds are of equal intensity, we may hear one as louder than the other because our ears detect it better than the other sound. Loudness depends on two main factors :

(a) Intensity of sound which is directly proportional to the square of the amplitude of the sound wave.

(b) Sensitivity of the ear.

Fig. 12.16 shows the wave shapes of a loud sound and a soft sound of the same frequency.

Fig. 12.16. Soft sound has small amplitude and louder sound has large amplitude.

(ii) Pitch. Pitch is the sensation which helps a listener to distinguish betwen a high and a grave note. Pitch depends on frequency. The faster the vibration of the source of sound, the higher is the frequency and higher is the pitch, as shown in Fig. 12.17. Thus a high pitch sound corresponds to more number of compressions and rarefactions passing a given point per unit time.

Fig. 12.17. Low pitch sound has low frequency and high pitch sound has high frequency.

The voice of a child or a lady is shriller than that of a man i.e., the pitch of a lady’s sound is higher than that of a man. The mosquito’s sound is of high frequency and hence high pitch.

(iii) Quality or timbre. The quality or timber of sound is that characteristic which enables us, to distinguish one sound from another having the same pitch and loudness. It is due to the quality of sound that one can recognise the voice of one’s friend without seeing him.