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Current time:0:00Total duration:8:57

Video transcript

whenever I'm up at the mountains I usually like to shout you and I hear myself over and over again you may be familiar with this it's called an echo on the other hand if you are inside a big empty room which doesn't have enough people in it or hardly has any furniture or carpets or cushions and you start speaking over there then you sound something like this testing one two three this is what it sounds like it's a little annoying because sometimes you can't understand what people are saying this is called a reverberation but what exactly is this reverberation and why does it happen in empty rooms and why do we hear these echoes at mountains well that's exactly what we learn in this video we'll see what these things are why do they occur and we will also learn how to reduce these effects to improve the sound quality all right the main reason for echoes and reverberation is because sound can reflect so for example when you are at the mountains and you shout yo the sound waves keep traveling forward until it meets an obstacle in this example another mountain and just like how when light waves or water waves hit an obstacle some of it bounces back similarly over here some of our sound waves who also bounce off that mountain making its way back towards you and finally you will hear a second yo and this process can keep continuing giving us multiple echoes but of course you may know that a sound travels more distance it becomes more and more feeble and so the subsequent echoes that you hear will become more and more feeble and after three or four reflection you can no longer hear it so let's look at this effect one more time you but what isn't the same thing happen when we are inside an empty room why can't the walls of the room reflect sound and make us hear echoes well they do reflect sound but they are much closer to us compared to the mountains and as a result we hear the reflected sound much quicker and so when the sound undergoes multiple reflections the time gap between each subsequent reflection that we hear is very small and as a result our brains cannot tell when one sound ended and when the next reflected sound began now to understand this better we can actually go ahead and do a demo so in this editing software I have copied the original your sound and pasted it multiple times to simulate the echoes now when we play this will first hear this sound the original one then the first reflection then the second reflection and the third and fourth and the gap that have kept now in in this case between each sound is about 0.8 seconds so let's play and see what we hear here goes you this was very similar to the mountain case I'm pretty sure you could clearly distinguish between the different reflected sounds so we will call this as echoes and so as we saw 0.8 seconds is big enough for our brains to differentiate between the different reflected sounds so let's reduce that gap and see what happens now I have made that gap 0.4 seconds let's see if we can hear the echoes here goes you again I'm pretty sure you could still hear the individual sounds the individual reflected sounds let's play it one more time you so we will still call these as echoes even point four seconds is big enough for our brains to differentiate the sounds now we will make the time gap very small all right now the time gap is about point zero seven seconds so let's zoom in a little bit this time gap now is point zero seven seconds let's see if we can hear the individual echoes here goes you could you hear it let's play it one more time close your eyes and see if you can actually hear the individual echoes here goes you I don't know about you but I couldn't tell the distinct echoes anymore I couldn't tell when one sound ended and when the next one began and it's for this reason we won't call this as echoes anymore so let's hear it one more time you so these successive reflections are only prolonging that original sound in our head and this prolongation of the sound our persistence of the sound in our ears due to these successive reflections is what we call reverberation I mean some specially constructed buildings like the go Kumba's of Bijapur or in some caves the reflections can be very strong and instead of hearing just for reflections here we can easily hear fifty to sixty reflections giving us an extremely strong reverberation so let's let's simulate what that would sound like so here's what reverberation sounds like with about fifty to sixty reflections ready for this here goes you it's still there it's still there all right so if the time gap between successive reflections is a lot we'll call them as echos and if it's very small we'll call them as reverberation but one question we might have is how much time gap is needed for echoes and for reverberation well research shows that if the time gap is more than 0.1 second then we can hear the sounds distinctly and then we'll call them echoes and so if the time gap is less than 0.1 seconds then our brains can tell when one sound ends and the next one begins and that's when we call them reverberation and of course at the time is close to 0.1 second it could be a gray area it could be sort of an echo and reverberation together and lastly how do we reduce reverberation whether you want to deliver a speech in a large hall or I want to record my videos over here reverberations can make it difficult to understand what people are saying so in such cases we need to reduce it as much as possible and that can be done by introducing sound absorbing materials in your room because if sound gets absorbed then there will be less reflection less reverberation this can be done by having open windows or carpets cushions and even people and for the same reason in my room I have this sound absorbing foam this beanbag this carpet and a very questionable blue curtain all these things absorb sounds and reduce reverberation so what did we learn in this video we saw that if the time gap between the original sound and the reflected sound is big enough at least about 0.1 second then we hear echoes and if it's less than 0.1 seconds then our brains cannot identify the individual sounds and recall it reverberation an excessive reverberation can be annoying and so we can reduce it by introduced in sound-absorbing things