Psychological Characteristics of Sound

Psychological Characteristics of sound: A sound has three characteristics such as loudness, pitch and quality (or timbre).

1. Loudness: It is the measure of the sound energy reaching the ear per second. Greater the sound energy reaching our ear per second, louder the sound will appear to be. If the sound waves have a small amplitude, then sound will be faint or soft but, if waves have a large amplitude, then the sound will be loud. Figure given shows the wave shapes of a loud and a soft sound of the same frequency.

Characteristics of loudness of sound:

1. Since, the amplitude of a sound wave is equal to the amplitude of vibrations of the source producing the sound waves, hence the loudness of sound depends on the amplitude of vibrations of the source producing the sound waves.

2. Loud sound can travel a larger distance as it is associated with higher energy.

3. A sound wave spreads out from its source, as it moves away from the source, its amplitude as well as its loudness decreases. The loudness of sound is measured in decibel (dB). It depends on the sensitivity or the response of our ears.

2. Intensity: The amount of sound energy passing each second through unit area is known as the intensity of sound. Loudness and intensity are not the same terms. Loudness is a measure of the response of the ear to the sound. Even when two sounds are of equal intensity, we may hear one as louder than the other, simply because our ear detects it in better way. The SI unit of intensity is watt per square metre ( $W/m^2$ )

2. Pitch or Shrillness: It is that characteristic of sound by which we can distinguish between different sounds of the same loudness. Due to this characteristic, we can distinguish between a man’s voice and woman’s voice of the same loudness without seeing them. Pitch of a sound depends on the frequency of vibration. Greater the frequency of a sound, the higher will be its pitch. In other words, the faster the vibration of the source, the higher is the frequency and hence higher is the pitch, as shown in figure. Thus, a high pitch sound corresponds to more number of compressions and rarefactions passing through a fixed point per unit time. Low pitch sound has low frequency and high pitch sound has high frequency.

3. Quality or Timbre: The quality or timbre of sound is that characteristic of sound which enables us to distinguish one sound from another having the same pitch and loudness. The pleasant sound is said to be of a rich quality. A sound of single frequency is called a tone. The sound produced due to a mixture of several frequencies is called a note and is pleasant in listening too. Noise is unpleasant to ear, music is pleasant to ear and is of rich quality.

Sample Questions

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Question : 1

In order to reduce the loudness of a sound we have to
A. Decrease its frequency of vibration of the sound.	B. Increase its frequency of ibration of the sound.	C. Decrease its amplitude or vibration of the sound	D. Increase its amlitude of vabration of the sound
Right Option : C
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