All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > The Projects Forum

Notices

The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

Reply   Post New Thread
 
Thread Tools Display Modes
  #1  
Old 12-04-2011, 04:11 PM
cycleops cycleops is offline
New Member
 
Join Date: Dec 2011
Posts: 3
Default noise cancellation circuit

Hi,

I'm looking for advice on the suitability of using this noise cancellation circuit to (hopefully) improve speech recognition app running on my home theater pc:
http://gilmore2.chem.northwestern.ed.../noise_prj.htm

I thought of using the audio out connections of my receiver/amp as input to J1 and the mic as input to J2. The mic would be about 12 feet from the speakers.

Does anyone think this would, or would not, work?

BTW, I am an electronics beginner.
Reply With Quote
  #2  
Old 12-04-2011, 04:50 PM
SgtWookie's Avatar
SgtWookie SgtWookie is offline
Expert Member
 
Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,038
Default

What is it that you are trying to do?

Perform speech recognition while playing a movie?

It might help cancel a fair bit of the noise, but will likely be less effective in the higher frequencies due to the propagation delay (lag) between the line-level output, and output that goes through the amplifier, speakers, and then acoustic sound that travels through the air 12 feet to the microphone.

That circuit has only a very small amount of propagation delay from the mic input to the cancellation of noise.
__________________
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
Reply With Quote
  #3  
Old 12-04-2011, 04:56 PM
kubeek's Avatar
kubeek kubeek is online now
Senior Member
 
Join Date: Sep 2005
Location: Prague, Czech Rep
Posts: 3,485
Default

Quote:
Originally Posted by cycleops View Post
Hi,

I'm looking for advice on the suitability of using this noise cancellation circuit to (hopefully) improve speech recognition app running on my home theater pc:
http://gilmore2.chem.northwestern.ed.../noise_prj.htm

I thought of using the audio out connections of my receiver/amp as input to J1 and the mic as input to J2. The mic would be about 12 feet from the speakers.

Does anyone think this would, or would not, work?

BTW, I am an electronics beginner.
I donīt see how are noise-cancelling headphones gonna help with recording sounds for speech recognition. Subtracting speaker signal from the mic wonīt help at all.

With headphones it helps because the path between the speaker and mic is very short.
To do the same for recording, you would have to shove a mic into your mouth, which defies recording with another mic.
Reply With Quote
  #4  
Old 12-04-2011, 05:24 PM
praondevou's Avatar
praondevou praondevou is offline
Senior Member
 
Join Date: Jul 2011
Location: Canada
Posts: 2,887
Default

I hate when they say "noise cancellation" when it's actually noise attenuation. If there only was such a thing like complete noise cancellation. Not even they most expensive headphones manage to cancel noise...
__________________

Reply With Quote
  #5  
Old 12-04-2011, 06:36 PM
cycleops cycleops is offline
New Member
 
Join Date: Dec 2011
Posts: 3
Default

Quote:
Originally Posted by SgtWookie View Post
What is it that you are trying to do?

Perform speech recognition while playing a movie?

It might help cancel a fair bit of the noise, but will likely be less effective in the higher frequencies due to the propagation delay (lag) between the line-level output, and output that goes through the amplifier, speakers, and then acoustic sound that travels through the air 12 feet to the microphone.

That circuit has only a very small amount of propagation delay from the mic input to the cancellation of noise.
Yes, I do want to perform speech while watching movies (pause, volume, play, etc...). I'm using voxCommando (http://voxcommander.com) and it works surprisingly well, but I'm hoping to improve its success rate.

To clarify for kubeek, there are no headphones involved with my intended use. The circuit would invert the signal from my receiver/amp and apply it to the signal from a mic sitting on a shelf. So the circuit attenuates sounds from the amp (like a CD I'm playing), and more clearly hears my speech via the mic (like me saying "pause music"). It feeds my speech into my home theater pc where voxCommander recognizes and acts on the speech.

I'm wondering if the lag SgtWookie mentions will prevent attenuation.
Reply With Quote
  #6  
Old 12-04-2011, 07:09 PM
kubeek's Avatar
kubeek kubeek is online now
Senior Member
 
Join Date: Sep 2005
Location: Prague, Czech Rep
Posts: 3,485
Default

The mic and the speakers would have to be bolted to floor for this to work at least a bit with a simple circuit.
Unfortunately the direct wave from the speaker mixes with the reflections off all surfaces. You would need two circuits which delay the L and R speaker signal and mix it with the mic signal, but I doubt if will have any cancelling effect.

I can suggest you one thing, take a piece of music or anything, play it through one speaker only and record the result, without any other noise. Then put the original singal and the record into software editor, for example cooledit would work nicely, and try your best at combining the two (addition or subtraction + delay, maybe some equalizer) and see if you can make anything out of it that has at least lower volume than the original mic signal is, i.e. try cancelling the two to get zero signal.

If you succeed, then you will have the recipe how should the circuit look like to get the result. Much easier than blindly building and testing. Also then try recording again and see if it still works

P.S. you can add multiple copies of the original to tame the larger reflections

Last edited by kubeek; 12-04-2011 at 07:19 PM.
Reply With Quote
  #7  
Old 12-04-2011, 10:25 PM
cycleops cycleops is offline
New Member
 
Join Date: Dec 2011
Posts: 3
Default

Quote:
Originally Posted by kubeek View Post
The mic and the speakers would have to be bolted to floor for this to work at least a bit with a simple circuit.
Unfortunately the direct wave from the speaker mixes with the reflections off all surfaces. You would need two circuits which delay the L and R speaker signal and mix it with the mic signal, but I doubt if will have any cancelling effect.

I can suggest you one thing, take a piece of music or anything, play it through one speaker only and record the result, without any other noise. Then put the original singal and the record into software editor, for example cooledit would work nicely, and try your best at combining the two (addition or subtraction + delay, maybe some equalizer) and see if you can make anything out of it that has at least lower volume than the original mic signal is, i.e. try cancelling the two to get zero signal.

If you succeed, then you will have the recipe how should the circuit look like to get the result. Much easier than blindly building and testing. Also then try recording again and see if it still works

P.S. you can add multiple copies of the original to tame the larger reflections
I think you're right, there would be no canceling. Thanks.
Reply With Quote
Reply   Post New Thread

Tags
, , , ,


Related Site Pages
Section Title
Worksheet Calculus for electric circuits
Worksheet CMOS logic gates
Worksheet Summer and subtractor opamp circuits
Worksheet Negative feedback opamp circuits
Worksheet Superposition theorem
Worksheet Electrical noise and interference
Worksheet Passive integrator and differentiator circuits
Worksheet Resonance
Textbook Radio circuits -- INCOMPLETE : Practical Analog Semiconductor Circuits
Textbook BJT quirks : Bipolar Junction Transistors


Similar Threads
Thread Thread Starter Forum Replies Last Post
Phase Noise In PLL lkgan General Electronics Chat 0 05-24-2010 11:47 AM
Noise Cancellation Project Idea supedave The Projects Forum 6 03-15-2010 09:27 PM
Amplifier circuit!?! Urgent Help Needed! johnjoe2000 Homework Help 2 12-06-2009 07:46 PM
Cold Plasma Circuit ablaty The Projects Forum 7 11-08-2009 05:31 PM
Help with "noise" in Time Delay Circuit Newbee The Projects Forum 7 06-11-2008 06:15 AM

Thread Tools
Display Modes

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

Forum Jump


All times are GMT. The time now is 08:00 PM.


User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin
Copyright ©2000 - 2014, vBulletin Solutions, Inc.