Active Noise Cancellation - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th February 2003, 01:51 AM   #1
manse is offline manse  United States
diyAudio Member
 
Join Date: Feb 2003
Location: NY
Send a message via AIM to manse
Question Active Noise Cancellation

Does anyone have any experience or comments on active noise cancellation as a means of reducing background noise? I'm looking for sources of information and starting points for a possible project. I've seen these headsets from Sony and others that seem to be based on a pretty cool concept, but I've heard complaints about them not working very well. Does anyone have any idea what these units are actually doing?
  Reply With Quote
Old 15th February 2003, 02:21 PM   #2
diyAudio Member
 
MRehorst's Avatar
 
Join Date: May 2002
To paraphrase our lubricious former leader, "That depends on what the definition of well is"...

Those headphone put a small microphone close to each ear to sample the acoustic noise there. The microphone is amplified and fed into the earphone, but the phase is inverted, so the noise is cancelled at your ear. This works mainly for low frequencies for a number of reasons- there is a physical distance between the mic and your ear and the earphone. High frequencies with very short wavelengths may actually be reinforced rather than canceled. But that generally isn't a problem because the inverting amplifier's high frequency response is rolled off to keep the whole system stable. So you get noise cancellation at low freqs with less and less effectiveness as the frequency goes up.

I have some Sony in-ear noise cancelling phones. They are great on airplanes and trains- they allow me to listen to movies or music at a reasonably low volume level because I don't have to crank up the volume to drown out the noise from the vehicle.

MR
__________________
Keeping an open mind since 2002...
  Reply With Quote
Old 15th February 2003, 02:57 PM   #3
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Default we use Bose

in our airplane -- expensive but they work great and your head doesn't ring at the end of a long flight.
  Reply With Quote
Old 15th February 2003, 11:48 PM   #4
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Actually, the most sophisticated noise cancelling headphones
and such don't use inverting feedback in the usually understood
sense. Rather, they use DSP to analyze repetitive noise and
have an algorithm to produce its phase opposite. This way
you can hear other things which are not long term repetitive.
  Reply With Quote
Old 16th February 2003, 12:26 AM   #5
manse is offline manse  United States
diyAudio Member
 
Join Date: Feb 2003
Location: NY
Send a message via AIM to manse
OK thanks everyone for the feedback but I am more interested in building one of these headsets myself. Not necessarily to save money, but to figure this concept out and play with it a little. Would a simple inverting op-amp circuit and a correctly placed mic/speaker set do the job or is there more to it than that(Adaptive DSP logic aside, that may come later...)?
  Reply With Quote
Old 16th February 2003, 09:50 AM   #6
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Have a look at this project on Headwize, it might give you some ideas
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 18th February 2003, 06:04 PM   #7
diyAudio Member
 
Da5id4Vz's Avatar
 
Join Date: Feb 2003
Location: lost in america...
Send a message via AIM to Da5id4Vz
These were the 1st pair I saw, almost 10 years ago, and not too shaby:

http://www.nct-active.com/nbex.htm

NCT is an interesting company. Their web site is work a browse.

The Headwize article is very interesting.
  Reply With Quote
Old 31st March 2003, 04:57 PM   #8
Entropy is offline Entropy  United States
diyAudio Member
 
Join Date: Feb 2003
Location: Bridgewater, NJ
I've built the Ryckebush design.

It works well. It has its limitations, but it's an AMAZING help on airplanes. It's the difference between being able to hear or not hear your movie or music.

Which reminds me, I have to fix the circuit/clean it up now that security is a bit stricter. (And I need to figure out a better power source than two 9V batteries.)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
software noise cancellation / antisound jackpipe Digital Line Level 13 11th May 2010 08:13 PM
Active noise cancellation for a computer? MikeHunt79 Everything Else 0 3rd April 2008 10:54 PM
active voice cancellation chusubaxt Car Audio 7 27th November 2007 03:51 AM
Active Noise Cancellation gcladis Pass Labs 4 27th June 2006 11:36 PM
'active feedback' for distortion cancellation scott wurcer Solid State 32 31st January 2005 04:49 PM


New To Site? Need Help?

All times are GMT. The time now is 02:30 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2