Here topic covered: -Acoustics definition, Classification of Sound, Characteristics of musical sound, Properties of Noise

Acoustics definition, Classification of Sound, Characteristics of musical sound, Properties of Noise

Acoustics –

Physics dealing with generation, propagation, and applications of sound.

Acoustics is the science of sounds which deals with the properties of sound waves.

The architecture of Acoustics- Physics dealing with the construction of buildings with an intention to provide good audible sound to the audience.

Soundwaves- Any vibrating body will displace the air layers nearby and initiate a mechanical wave which propagates in the medium through alternate compression and rarefactions, sets the eardrum vibrating and causes the sensation of hearing.


BA Rarefaction



  1. Infrasound 20 Hz)
  2. Audible sound ( 20 Hz – 20K Hz)
  3. Ultrasound (more than 20K Hz)


Classification of audible sound:-

(a). Musical Sound (b). Noise



Musical Sound: The sound which produces the pleasing effect on human ear is called musical sound.

Example: -sitar,violin,flute,piano, etc.

Properties of musical sound:

  1. Regular waveforms
  2. Definite periodicity
  3. No sudden change in amplitude

Noise: – The sound which produces an unpleasing effect on human ear is called noise.

Example: – road traffic,crackers, etc.

Properties of Noise:-

  • Irregular waveforms
  • Not definite periodicity
  • A sudden change in amplitude

Pitch: – related to a frequency of sound

Loudness:- related to an intensity of sound

Timbre: – related to the quality of sound


Pitch:      the pitch is a related frequency of sound. Pitch helps in distinguishing between a note of high frequency and low-frequency sound of the same intensity produced by the same musical instruments. This sound is produced by ladies and children with high frequency because of high pitch. This sound is produced by mosquito and bee with high frequency because of high pitch.

Loudness: –   a loudness characteristic which is common to all sound, whether classified as musical sound or noise. Loudness is a degree of sensation produced on an ear. Thus, loudness varies from listener to another. Loudness depends on the intensity of sound and depends upon sensitiveness of the ear. A relation between loudness and intensity:-

L-K log I

Loudness is directly proportional to the logarithm intensity l. Above relation is known as Weber Fechner law. On taking differentiation of above relation so we get a new quantity dL/dt which is termed as sensitiveness equation.

dL/dI = K

Where dL/dI is called sensitiveness of the ear. Loudness is physiological quantity.

Timber: It is quality of sound which enables us to distinguish between two sound having the same loudness and pitch. It depends on the presence of overtones. It helps in distinguishing between musical notes emitted by different musical instruments and voice of the different persons even though the sounds have the same pitch and loudness.

Intensity (I):-

The intensity of sound waves at a point is defined as the amount of the sound energy Q flowing per unit area in unit time.


Where A—area, t— time, Q— an amount of the sound energy If A—I m2 and t— 1 sec, then Intensity is a physical quantity which depends on factors like amplitude, frequency and velocity v of sound together with the medium. The unit of intensity is w/m²

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