Basics of Sound.pdf

This document covers the basics of Sound like propagation, Velocity, and Measurement of Sound.

1. Sound

By Prof. Hitesh Dholakiya

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2. Outlines

* Basics of Sound

< Propagation of Sound
« Velocity of Sound

< Measurement of Sound

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3. Basics of sound

+ Sound is pressure waves.
Q As it travels based on pressure difference.

«* Sound is longitudinal waves.
Q Amplitude of oscillation is there in the direction of propagation

« For Humans, sound waves are there in range of 20Hz to 20000Hz.

“In general, Females has higher frequency of tones as compared to
males.

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4. Basics of sound

< Sound is the sensation we perceive when vibrations in the air are
detected by our ears.

“ Our ears converts this vibrations into electrical impulses.
« These impulses are transmitted to our brain via our nervous system.

« Our brain then distinguishes its three main characteristics.
Q Pitch
Q Timbre
Q Loudness

5. Propagation of sound

He E hg

Compression

our ears picks

: hange in pressure
: refraction [918

Atmospheric Rarefractio vibration and then

Pressure transmit that to brain

Pressure

Time

6. Velocity of sound

« Sound velocity is directly proportional to root of Temperature.
va VT

« Here, Temperature T should be considered in kelvin.
“ At 20° C, velocity is 344 m/sec.

7. Measurement of sound

« Sound can be measure in terms of dB with pressure as per

Where, P = Pressure and Py = 2 x 10-5Pa

< Sound can be measure in terms of dB with Power as per

(W 2
Iw= 10108 (y ) Where, W = Power and W, = 10712W
\Wo

« Sound can be measure in terms of dB with Intensity as per

LP)
Lp = 20108(=-)

Po)

) Where, | = Intensity and I) = 10712W/m2

(1
= 101087,
do,