# Doppler effect of sound : what happens when velocities of source and observer are comparable to velocity of sound

Doppler effect : what happens when velocities of source and observer are comparable to velocity of sound

My text says that Doppler effect is applicable only when the velocities of source and observer are less as compared to the velocity of sound , whereas in a reference book (waves by D.C.Pandey ) I came across a problem in which they actually used Doppler effect when source velocity was equal to that of sound.

• As you might have noticed while using a whip, it produces a load bang. This is because it exceeds the speed of sound. And in the moment when the speed of a whip is comparable to the speed of sound, the sound amplifies. Though I'm also curious to how long that would amplify the sound. – MaDrung Feb 6 '17 at 8:47
• Well so in terms of quantititative analysis would that mean that the loud bang - is independent of the actual frequency or rather independent of the Doppler effect ,I would seek more explanation on this topic – Aditya Sher Feb 6 '17 at 8:52
• If the source is moving and the observer is stationary then the relevant equation is $f_{\rm observer} = \dfrac {v_{\rm sound}}{v_{\rm sound} - v_{\rm source}}f_{\rm source}$. I do not think that your could a better explanation than in this link which has some nice animations acs.psu.edu/drussell/Demos/doppler/doppler.html – Farcher Feb 6 '17 at 10:15