The apparent frequency of sound heard by an observer moving towards a stationary source with speed vo is n1. If the observer moves away from the same source with the same speed, the observed frequency is n2. If the speed of sound in air is 340 m/s and n1 : n2 = 71 : 65, what is the speed of the observer?

At what speed should a source of sound move away from a stationary observer so that the observer hears an apparent frequency equal to half of the original frequency? (where v is the speed of sound)

When both the source of sound and the listener are approaching each other, the observed frequency of sound is given by which formula? (where VL and VS represent the velocities of the listener and source respectively, V is the speed of sound, and n0 is the emitted frequency)