Question

what is the minimum length of hall that can form a clear echo event that the speed of sound in dry air is 350 metre per second​

Answer 1

Answer:

reflecting object must be more than 17.2m

Explanation:

for the temperature of 25 degree celeus for this the reflecting object must me >17.2m

Answer 2

Answer:

17.5 m

Explanation:

The sensation of any sound persists in our ear for about 0.1 seconds. This is known as the persistence of hearing. If the echo is heard within this time interval, the original sound and its echo cannot be distinguished. So the most important condition for hearing an echo is that the reflected sound should reach the ear only after a lapse of at least 0.1 second after the original sound dies off.

As the speed of sound is 350 m/s, the distance travelled by sound in 0.1 second is 35 m. This is twice the minimum distance between a source of sound and the reflector. So, if the obstacle is at a distance of 17.5 m at least, the reflected sound or the echo is heard after 0.1 second, distinctly.

Hence, to hear a clear echo, the minimum distance between the reflecting surface and the observer is 17.5 m.