Naked Science Forum
General Science => General Science => Topic started by: Geezer on 18/02/2010 22:13:37
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I've been inside anechoic chambers a few times, and it's really quite difficult to talk normally. Presumably we depend on the echo of our own voice when we are speaking, but I suspect the real answer is more complicated than that.
Any suggestions?
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I've been inside anechoic chambers a few times, and it's really quite difficult to talk normally. Presumably we depend on the echo of our own voice when we are speaking, but I suspect the real answer is more complicated than that.
Any suggestions?
I'm really curious about this Mr Geezer.
When ewe say it's difficult to speak, do ewe mean it's difficult to hear yourself or that it is physically difficult to vocalise ! ?
Please describe this curious experience.
I can understand if there were piccys of me displayed in the chamber as most people are breathless at my mere image...but I suspect ewe are referring to something quite different.
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Would the same thing happen if you tried to talk with noise-canceling headphones on? Unfortunately, with the economy the way it is I've had to cancel my order for an anechoic chamber.
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Yes. I would think noise cancelling headphones will have a similar effect, although I do have a pair and I can't say I've noticed it. It's been a while since I was in an acoustic anechoic chamber.
I just remember it was very weird sensation and it was quite difficult to conduct a normal conversation. Perhaps when you are wearing headphones it gives you a cue that things are going to sound different.
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I think that a slightly different, but related, phenomenon occurs when broadcasting; we wear headphones to hear what we sound like, what the other presenters sound like and what people in remote studios or on telephone lines are saying.
But, owing to the processing that the signal goes through, the headphone signal can be delayed under certain circumstances by anything up to 50ms; this means that you hear yourself saying what you just said slightly after you just said it. The effect is as though you are being hit with a very short latency echo - essentially the reverse of the anechoic chamber.
When I first experienced this I found it extremely disconcerting and very off-putting. But, pretty quickly, I stopped noticing it. I think this is down to re-learning how we monitor what we are saying.
I also think the anechoic chamber example is a similar - but reversed - manifestation of the same phenomenon.
Chris
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The anechoic chamber effect is probably similar to trying to speak with earplugs in or when using headphones (with no sound coming out). You can end up speaking the way some people who are profoundly deaf speak. It is the like of the correct feedback. I think you can get used to it and compensate, but it isn't easy.
The problem with hearing an echo is a slightly different problem I think. You also used to get this when connected by phone on a transatlantic call when the connection is via satellite. It does not happen much today because most phone connections are made via landline now (fibre optic), with a minimal delay, and not satellite. Also, echo cancellation techniques have improved. From the brain's perspective hearing your own voice delayed is very disconcerting and has the effect of making you hesitate. Again, as Chris says, you can ignore it with practice. I am very surprised this occurs in a studio environment though. Such a long delay is not necessary as far as I can see. It will be occurring because of digital processing I expect. As a matter of interest the spec for radio microphones (including the new digital ones) is that there should be something like no more than 3ms delay.
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... the spec for radio microphones (including the new digital ones) is that there should be something like no more than 3ms delay.
A latency of 10 milliseconds or better is the target for audio circuits within professional production structures, local circuits should ideally have a latency of 1 millisecond or better.
http://en.wikipedia.org/wiki/Latency_%28audio%29
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Graham and RD, thanks.
Low-latency is the case for analogue setups with direct monitoring; for instance a small home-studio with a mic and mixer and a set of headphones. Studios, even when using digital output processing, will have a minimal delay analogue monitor return so that the guests and presenters hear themselves in real time to avoid disconcerting echoes.
But sometimes it's necessary to listen to a mix that, before reaching the headphones, has been through digital signal processing (DSP). This often involves look-ahead limiting, which introduces a delay of 10-50ms. My DSP is about 12ms; when monitoring off the mix it makes you sound "growly" or gruff in the headphones. This is because your ears get the first version of what you say via bone conduction, and then the second version, delayed, via the air conduction (via the phones).
The benefit of listening to what comes out of the DSP is that what you hear is what you get, so to speak. Recording processed audio whilst monitoring only unprocessed audio requires a lot of faith and confidence in your equipment!
Chris
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RD, having recently seen a "Request For Quote" from a major microphone manufacture I can tell you that their requirement was for 3ms, including A-D, digital (DQPSK) modulation and wireless transmission. There will be some decoding delay at the receiver end too. This isn't too bad when you think that this is like listening to someone about 3 feet away.
I don't think look ahead limiting need take that long Chris, though generally audio compression algorithms are employed, which can be slow. Theoretically all of this can be much faster, so I would expect to see better studio equipment in the future.