A small source of sound moves on a circle as shown in figure and an observer is sitting at O. Letv1, v2,v3be the frequencies heard when the source is at A, B and C respectively

Dear student,
The frequency heard when the source is at C is maximum and is equal when the source is at A and B at the particular instant of time.
The frequency would gradually decrease as the source moves from A onwards and the frequency would gradually increase as the source moves from B onwards.
Regards
Sumit