Cancelling an Audio Signal

[purifier]

There's a lot of traffic in front of my house... At times it becomes difficult for me to study... I got an idea recently... I don't know if it has been already implemented but here's the idea... What if we could design a device which clings to our ear and cancels all the audio signals which reach the ear... I mean it should analyse the signal and then produce a negative of the same signal so that both can cancel out each other... Is this possible? Please help...

 

[IanP]

What you really need is to invert signal polarity using linear inverting amplifier with automatic gain control (here you can use an audio compressor). In confined space such as a room you possibly will be able to cancel partials of this complex audio signal ..

 

[artem]

you should put 2 sensors - one outside (a) and one near your ear(b) . Then you should perform math such as :

b - a*k = c is signal you should send to your ear .

Your system should calculate signal transfer coefficient k in real time as if you will change the possition and signal level from outside received at your ear will be changed .

But because of sound reflections from walls in your room and different way the noise is coming from outside you wont able to cancel noise fully -
signal sources will have different phase and different levels compared to what you got from sensor a.

If i am not wrong it is not new idea - i heard about that few years ago.

Other solutions include :

- try to give up study first
- if you can't - brick the window.
- then change the house if walls are too thin
- and finally destroy outside road with explosives if you are little bit lazy to do above

 

[M!k]

it's called anti-sound. Practical application:
https://www.sonicshop.de/English/Cont/Plugs/PXC250.htm


Mik

 

[purifier]

That info was really useful... Hope i could get more... I heard that the same technology is used in some planes...

And one more thing... I found this circuit somewhere hidden in my system... Well, don't know where i got it from but heres the circuit... I'll try to dig up the links too...

 

[artem]

If you are not going to hear anything - it will be very easy to adapt this circuit to make auto gain tuning .

But if you would like to just block outside noice and pass internal room sound - that is very challenging .

 

[purifier]

In that case... we'll make something that can block everything... Absolute silence!!!

 

[skydiverc]

This technology is used in many aircraft headsets.
Its typically called noise cancellation.

After reading purifiers last comment I was immediatly taken back to when I was a kid watching Get Smart.
Anyone else remember the "Cone of Silence" roflmao...

 

[wwfieee]

here is a link to ear plug. quite good, it blocks almost everysound. this is used by people who cut timbers with chainsaws. have you ever hear chainsaws at full speed? it's damn loud. and this cuts it down pretty much. imagine what it would do in your room.

http://www.usa.husqvarna.com/?url=/node1573.asp?cid=201&frames=false

ignore other protections unless your room is really in a nasty environment.