What is an echo? Mention the condition for the echo to be heard.
Echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is proportional to the distance of the reflecting surface from the source and the listener.
The conditions necessary for hearing the echo:
The distance between the sound source and the reflecting surface must not be less than 17 metres where the time period between hearing the original sound and its echo should not be less than 0.1 of a second .
The human ear can not distinguish between two successive sounds if the period between them is less than 0.1 second , Wide and big reflecting surface must be presented to hear the echo such as the walls , the mountains or the water bodies .
The velocity of sound through the air is 340 m / sec , so the distance travelled by the sound and its echo in 0.1 sec = 34 metres , The distance travelled by the sound is 17 metres from the sound source to the reflecting surface and 17 metres from the reflecting surface to the ear ( echo ) .
The echo can not be heared if the distance between the sound source and the reflecting surface is less than 17 metres because the time between hearing the main sound and its echo will be less than 0.1 of a second , and the human ear can not distinguish between the two successive sounds .
When the distance between hearing the main sound and the reflecting surface is multiplies of 17 metres ( twice or three times ) , the echo is heard in the form of the last two or three phrases of the whole produced sound .
Echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is proportional to the distance of the reflecting surface from the source and the listener.
The conditions necessary for hearing the echo:
The distance between the sound source and the reflecting surface must not be less than 17 metres where the time period between hearing the original sound and its echo should not be less than 0.1 of a second .
The human ear can not distinguish between two successive sounds if the period between them is less than 0.1 second , Wide and big reflecting surface must be presented to hear the echo such as the walls , the mountains or the water bodies .
The velocity of sound through the air is 340 m / sec , so the distance travelled by the sound and its echo in 0.1 sec = 34 metres , The distance travelled by the sound is 17 metres from the sound source to the reflecting surface and 17 metres from the reflecting surface to the ear ( echo ) .
The echo can not be heared if the distance between the sound source and the reflecting surface is less than 17 metres because the time between hearing the main sound and its echo will be less than 0.1 of a second , and the human ear can not distinguish between the two successive sounds .
When the distance between hearing the main sound and the reflecting surface is multiplies of 17 metres ( twice or three times ) , the echo is heard in the form of the last two or three phrases of the whole produced sound .
