[burjo]

I am a student studying Architecture and am interested in sound and accoustics.

I have recently been informed about the Sennheiser HD-451 headphones. I don't know how they work exactly but am interested in this idea - ie how sound can be cancelled out through it's reversal and would like to incorperate it somehow in the design of my 6th year project.

I am absolutely ignorant of the subject but would appreciate any info or links to web sites that might help me.

Many thanks

burjo

 

[Budgie]

Hear is a link to help you get started:

http://www.ti.com/sc/docs/general/ds...000/niu001.pdf

Additional material should be avaliable by web search with the key words in this paper.

 

[gerG]

Noise cancellation headphones work because they are right at the receiver (your ears). They only have to cancel what reaches the receiver, and can respond very quickly to short duration sounds. The proximity also allows them to work up to fairly high frequencies. The farther away from the ears the microphone gets the lower the threshold frequency becomes due to phase shifting, and the problem gets very complex. The largest scale application that I have seen was the Lotus system used in a car (Esprit, I think). They were trying to cancel LF road noise. This is feasible since the entire cabin is in phase at low frequencies. It would take a pretty good subwoofer, though.Unfortunately I could not talk the dealer into letting me take the car for a spin to try it.