Question

Calculate the time for which the sensation of sound persists in

our brain if the minimum distance of the obstacle from the

source of sound is 17.2m (speed of sound in air =344m /s)

Answer 1

Hey friend here is your answer.......................

 As the sensation of sound persists in our brain for about 0.1 s, to hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1s. If we take the speed of sound to be 344 m/s at a given temperature sound must go to the obstacle and reach back the ear of the listener on reflection after 0.1s.   Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) ×0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance. I.e., 34.4/2 = 17.2 m

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