What is the minimum distance for an echo?

Answer 1

It depends on the wavelength of the sound!!!!

To hear an echo of a continuous sound you must be a multiple of half a wavelength away from the 'wall' (or whatever) the echo is coming off of. To hear an echo of a pulse, over a wavelength in distance is sufficient.

The A note is 440 Hz, and in air travels at about 330 m/s. This means the wavelength of the A note is about 75cm. If you play an A on the guitar and stand 75cm from the wall there WILL be an echo (whether you can hear it or not, remember if you stand this close to the wall the echo will come back about 2 milliseconds after the START of the note, so you wouldn't be able to distinguish the echo from the note). The echo will be there, but you won't be able to hear it.

Now, if you want to play an A on your guitar for 1 second and stop playing... and hear the echo 1 second later... you should stand about 330 metres away.

It all depends on what you want to echo and how you want to hear it.

Answer 2

Echoes are heard if the reverberation time is more than 3 second and consecutive reflections is more than 1/15 of a second.

If the speed of sound is 330m/s at a particular temperature, in 1/15 second it travels a distance of 22m.

That is the reflecting object must be at distance of 11 m from us, if one side alone is considered.

If the distance is less than this then we will receive it soon and echo will not be heard.

If the distance is great and the intensity of sound reflected does not fall below the audible limit then we can here echo.

If the distance is such that for successive reflections it takes only 1/15 of a second, the other condition that the reverberation time must be more than 3 second should also be satisfied.

The reverberation time is the time for the original intensity of sound to fall to the audible limit.

Answer 3

For audible sounds, it's a matter of time. Are your ears sensitive enough to pick up an echo after only nanoseconds, microseconds, milliseconds or whole seconds?

Echos happen. The real point is do you hear them?

(In RADAR technology, return echos are limited by the duty cycle of the circuit. As long as the machine is transmitting, echos can't be heard. There is also a very small transition while the transceiver is shifting from transmit to receive where echos can't be heard. The total of these two elements determine the minimum range of a RADAR set.)

Answer 4

When dealing with audible frequencies, the human ear cannot distinguish an echo from the original sound if the delay is less than 1/10 of a second. Thus, since the velocity of sound is approximately 343 m/s at a normal room temperature of about 20°C, a reflecting wall must be more than 16.2 m from the sound source at this temperature for an echo to be heard by a person at the source.

any distance will do but for humans to detect it, it would need >16.2m as stated above

Answer 5

Any distance. You will not hear an echo one metre away because it is too close to differentiate the source of the sound and the return of it but the echo still exists.
An echo is just bounced air waves of objects that happens everywhere all the time unless you build a soft padded room that can absorb the sound energy.
Soft furnishings absorb sound energy that is why an empty room tends to sound louder when you make a noise in them.

Answer 6

Depends on the medium where you wanna hear the echo. Your ear will respond to any consecutive sounds having a time interval of 0.1 s. So, its time that matters and not the distance. But if you want to find distance, then you need to know the speed of sound in th medium where you are standing and multiply speed by 0.1 s and then divide by 2( because sound will first travel that distance and then come back to our ears so it will travel twice the distance, so you have to divide it by 2), then you will get distance. e.g. In air, speed is 332 m/s, so distance will be (332* 0.1)/2= 33.2/2= 16.6m.

Answer 7

A newly built room is producing echo. But after months or years there is no echo. a room with polished suface walls etc with no obstacles (to block the sound ) can produce echo. Even a small tiled bathroom can produce echo as a big hall

Answer 8

at less than about 35ms or so, the ear can't discern an echo. What we refer to today as an echo in music, also called a "slapback" echo, is about 100-150 ms (and up). At sea level sound travels around 1ft/ms, so that's about 150 ft or 50m.

Answer 9

17 m

Answer 10

17.5 m .... it is the minimum distance required for an echo...No wonder our voice echos in empty halls