Figure (16-E11) shows a person standing somewhere in between two identical tuning forks, each vibrating at


512 Hz. If both the tuning forks move towards right at a speed of 5.5 m s-1, find the number of beats heard by the listener. Speed of sound in air = 330 m s-1.


Let us assume that the fork in the left side is fork A and the other one is fork B.


Now, A they are moving, the fork A is reaching the person and the fork B is going away from the person. Hence, the frequencies will be,



And,



So, the beat frequency will be,





Here,


f0 = 512 Hz


v = 330 ms-1


vs =5.5 ms-1


Putting the values, we get,




1