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2 : SOUND - Coggle Diagram
2 : SOUND
5 DOPPLER EFFECT
You hear the high pitch of the siren of the approaching ambulance, and notice that its pitch drops suddenly as the ambulance passes you. That is called the Doppler effect. 
Refers to the change in frequency when there is relative motion between an observer of waves and the source of the waves
Doppler Shift - Change in sound frequency due to the relative motion of either the source or the detector.
-example: a passing car
When a vehicle with a siren passes you, a noticeable drop in the pitch of the sound of the siren will be observed as the vehicle passes. This is an example of the Doppler effect. An approaching source moves closer during period of the sound wave so the effective wavelength is shortened, giving a higher pitch since the velocity of the wave is unchanged. Similarly the pitch of a receding sound source will be lowered.
doppler wavelength change
doppler effect frequency
2 INTENSITY OF SOUND
:star:Sound intensity is the sound power as it passes through a given area
:star:I = P / Area… (W/m2)
:star:Io = 1 x 10^-12 W/m2 (threshold of hearing) .
:star:-Intensity Level, β, is a comparison of two sound intensities (Ratio).
LOUDNESS
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the amplitude of a wave indicates its energy. The greater the amplitude, the greater the energy.
-The intensity of a sound is proportional to the square of the amplitude of the sound wave. (E ≈ I ≈ A2)
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the intensity can be written in terms of the maximum pressure variation
7 DIFFRACTING AND SOUND
bending of sound around a barrier
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