Question

Why the time taken by the sound increase as the distance increases

Answer 1

The pitch of the siren of a Fire truck appears to change as the truck passes us due to the Doppler effect. Of course, to an observer on the truck, the pitch does not change at all. Since the speed of sound in air is essentially fixed, the perceived pitch of a tone is related to the wavelength of the sound.

Answer 2

The velocity of sound in air is approximately 330 m/s.

Let a sound wave with velocity v covers a distance d. The time(t) taken for the journey is d/v.

If the distance is increased to d1 taking the velocity same , the time for the journey (t1)is d1/v.

Comparing the two conditions ,

(d/v)/(d1/v)

= (d/v) * (v/d1)

= d/d1

= k (constant)

So if d>d1 , then t>t1