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TICKET ARCHIVE -> Acoustic feedback - mic and speakers - problems
RobinS - Dec 26, 2005 - 1:13 pm
By far the more comfortable and convenient way to communicate is via speakerphone as nothing needs to be worn or held to the ear. I would love to be able to use speakers and a microphone without the problem of acoustic feedback. I was wondering if a high quality noise cancelling mic would work well if the speakers were used at low volume. Or perhaps its the direction of where the speaker is radiating that is also important?
Natobasso - Dec 26, 2005 - 1:47 pm
The feedback you're getting is occurring exactly because you're using speakerphone and then amplifying the sounds you're hearing in a "feedback loop", so you'll need to isolate the sound you make from the sound that's reproduced in order to eliminate feedback.
With the speakers pointed toward you the chance for feedback is increased because, again, you're stuck in a feedback loop that increases incrementally until feedback (of the hendrix kind!) is produced.
How we musicians eliminate feedback is by making sure the microphone is out of the field of speaker dispersion, but this option won't help you because you're at low sound levels and need to hear what you and your other person are saying.
My gut feeling is you better stick with the headset because feedback is virtually unavoidable in this case. Or, try pointing your speakers away from your microphone.
With the speakers pointed toward you the chance for feedback is increased because, again, you're stuck in a feedback loop that increases incrementally until feedback (of the hendrix kind!) is produced.
How we musicians eliminate feedback is by making sure the microphone is out of the field of speaker dispersion, but this option won't help you because you're at low sound levels and need to hear what you and your other person are saying.
My gut feeling is you better stick with the headset because feedback is virtually unavoidable in this case. Or, try pointing your speakers away from your microphone.
RobinS - Dec 26, 2005 - 2:12 pm
Please put this back in the pool. I'm quite familiar with the points you made. I need someone who may have had direct experience with noise cancelling mics. Obviously a headset would solve this problem but for the reasons mentioned at the start, I'm trying to get this working without one. They are a major hassle, with the wires knocking things over, getting tangled, plus the discomfort of wearing one for several hours a day.
One point that would be interesting to know:
What is more important: sound amplitude (volume) or sound dispersion angle? If the only factor in feedback is the amplitude then a headset may be my only choice. However if the dispersion angle is a major factor, there is hope. I should mention that there is extremely low ambient noise in my work environment. Obviously no radios droning on in the background. The worst noise component presently is the wretchedly cheap high rpm fan used in the Mini. When I can replace that, the joy of seeing that pulvarized under a large sledehammer will be oh so satisfying.
One point that would be interesting to know:
What is more important: sound amplitude (volume) or sound dispersion angle? If the only factor in feedback is the amplitude then a headset may be my only choice. However if the dispersion angle is a major factor, there is hope. I should mention that there is extremely low ambient noise in my work environment. Obviously no radios droning on in the background. The worst noise component presently is the wretchedly cheap high rpm fan used in the Mini. When I can replace that, the joy of seeing that pulvarized under a large sledehammer will be oh so satisfying.
RobinS - Dec 26, 2005 - 2:15 pm
Afterthought: do you think there is any real time analyser software for Mac? I need something that can log the frequencies that a mic is picking up. If the feedback is occuring at narrow points, equalization might help tremendously.
Natobasso - Dec 26, 2005 - 10:05 pm
I don't know of any noise cancelling microphones, only headphones. What about a wireless headset? At least that would help you with the cord problem.
It's not background noise but the noise you're producing and then reproducing (feedback) that's the issue. I think you'll either have no volume or feedback and no in-between, really.
I'll put this back into the queue.
It's not background noise but the noise you're producing and then reproducing (feedback) that's the issue. I think you'll either have no volume or feedback and no in-between, really.
I'll put this back into the queue.
RobinS - Dec 27, 2005 - 12:38 am
>I don't know of any noise cancelling microphones, only headphones.
There are several though they are not designed for computer use. The plugs would have to be changed.
> What about a wireless headset? At least that would help you with the cord problem.
But not the comfort problem. Also I don't trust the radiation / health issue with something producing EMF right against my head for hours a day. It just doesn't seem worth it for the convenience.
> It's not background noise but the noise you're producing and then reproducing (feedback) that's the issue.
However to use speakerphone devices effectively there has to be an absense of background noise.
> I think you'll either have no volume or feedback and no in-between, really.
There always that point where the feedback overtakes everything like a cancer. If I'm under that threshold, I simply won't have any feedback. It might be possible.
There are several though they are not designed for computer use. The plugs would have to be changed.
> What about a wireless headset? At least that would help you with the cord problem.
But not the comfort problem. Also I don't trust the radiation / health issue with something producing EMF right against my head for hours a day. It just doesn't seem worth it for the convenience.
> It's not background noise but the noise you're producing and then reproducing (feedback) that's the issue.
However to use speakerphone devices effectively there has to be an absense of background noise.
> I think you'll either have no volume or feedback and no in-between, really.
There always that point where the feedback overtakes everything like a cancer. If I'm under that threshold, I simply won't have any feedback. It might be possible.
Drumhum - Dec 28, 2005 - 12:29 pm
When I use ichat for audio conversation I simply use my imac's in-built microphone (located at the bottom of the monitor screen) and listen via speakers which go via an amp connected to the audio output of the mac. I only get feedback when the speaker volume is above a certain level but I can have them at a very comfortable level before this happens.
As you are aware feedback occurs when the sound from the speakers being picked up by the mic is above a volume threshold. The volume the mic "hears" can only be reduced by
1) turning down the speakers
2) turning down the sensitivity of the mic (which will also reduce the volume of your voice for the listener
Having said this, what the mic "hears" can also be effected in other ways. eg...
Moving the mic further away from the speakers
Moving the microphone closer to the mouth (which means you'll need to turn the mic down in volume now that your voice will be picked up louder, which has the added effect of reducing the sound getting to the mic from the speakers)
Using a directional mic: a cardioid or hyper cardioid microphone (to give the technical term) will pick up sounds only from a certain direction.
To be honest, I think the best course of action is to get the mic as close to your mouth as possible. It also means the sound will sound less distant for your caller. A headset is perfect for this but if thats too uncomfortable perhaps a mic a on some sort of stand. I'm getting ideas of pulling the mic off a headset and taping it to a wire coat-hanger, erm...or something (!) but perhaps you can think of more elegant solutions!
Your idea of using eq to shape the sound, pulling out the frequencies that are causing the feedback is theoretically possible though I feel it may prove complicated in practice - you'd either need software to eq the sound to do this (and I don't know of any for this sort of application) or some extra hardware which I doubt will prove cost effective.
Mics advertised as "noise canceling" are not to remove feedback but to make external sound less obtrusive for your listener (eg to reduce engine noise in a car etc). They *may* help to reduce feedback but they will need to be quite close to your mouth to work - ie we're back to the headset again! The canceling process is not done by the mic but by the electronics its connected to. To be true, there is no such thing as a noise canceling microphone - only a mic connected to noise canceling circuitry.
software used for internet audio chat (like ichat) typically uses techniques to reduce feedback anyway and its possible that any "clever idea" you come up with could interfere with the software workings. just a thought.
When all is said and done, your best bet is to have the speakers as quiet as possible and to have the mic as close to your mouth as possible.
Hope that helps but feel free to get back to me if I can be of further help. For the record I do sound recording for a living - Microphones are the tools of my trade;-)
regards
tom
As you are aware feedback occurs when the sound from the speakers being picked up by the mic is above a volume threshold. The volume the mic "hears" can only be reduced by
1) turning down the speakers
2) turning down the sensitivity of the mic (which will also reduce the volume of your voice for the listener
Having said this, what the mic "hears" can also be effected in other ways. eg...
Moving the mic further away from the speakers
Moving the microphone closer to the mouth (which means you'll need to turn the mic down in volume now that your voice will be picked up louder, which has the added effect of reducing the sound getting to the mic from the speakers)
Using a directional mic: a cardioid or hyper cardioid microphone (to give the technical term) will pick up sounds only from a certain direction.
To be honest, I think the best course of action is to get the mic as close to your mouth as possible. It also means the sound will sound less distant for your caller. A headset is perfect for this but if thats too uncomfortable perhaps a mic a on some sort of stand. I'm getting ideas of pulling the mic off a headset and taping it to a wire coat-hanger, erm...or something (!) but perhaps you can think of more elegant solutions!
Your idea of using eq to shape the sound, pulling out the frequencies that are causing the feedback is theoretically possible though I feel it may prove complicated in practice - you'd either need software to eq the sound to do this (and I don't know of any for this sort of application) or some extra hardware which I doubt will prove cost effective.
Mics advertised as "noise canceling" are not to remove feedback but to make external sound less obtrusive for your listener (eg to reduce engine noise in a car etc). They *may* help to reduce feedback but they will need to be quite close to your mouth to work - ie we're back to the headset again! The canceling process is not done by the mic but by the electronics its connected to. To be true, there is no such thing as a noise canceling microphone - only a mic connected to noise canceling circuitry.
software used for internet audio chat (like ichat) typically uses techniques to reduce feedback anyway and its possible that any "clever idea" you come up with could interfere with the software workings. just a thought.
When all is said and done, your best bet is to have the speakers as quiet as possible and to have the mic as close to your mouth as possible.
Hope that helps but feel free to get back to me if I can be of further help. For the record I do sound recording for a living - Microphones are the tools of my trade;-)
regards
tom
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