Class 9 Physics Sound Pitch, Amplitude, Loudness, Intensity

Pitch, Amplitude, Loudness, Intensity

  • Pitch: Frequency determines the shrillness or the pitch of the sound. Higher the frequency, higher the pitch or it is said that the sound is shrilling. Lower the frequency, lower the shrill or pitch. Eg: Babies voice has more frequency and thereby more shrilling than an adult voice.


  • Amplitude: It is a measure of the loudness or softness of the sound. The magnitude of the maximum disturbance in the medium on either side of the mean value is called Amplitude of the wave, represented by the letter A.


  • Loudness: Loudness is the response of ear to the sound. Loudness is proportional to the square of the amplitude of the vibration body producing sound. The more the amplitude of vibration, the sound is the loud. The lesser the amplitude of vibration, the sound is feeble.

Loudness  =  k.(Amplitude)2  (where k is the proportionality constant)

The loudness is expressed in a unit called decibel (dB).


  • Intensity : The amount of sound energy passing each second through unit area is called the Intensity of Sound.




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