Home |
Search |
Today's Posts |
#1
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
Hi,
I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. * Does anyone know how effective such a mike/speaker combo could be, given that the interference pattern will be limited to a certain area, and outside of it, there would be less and less interference? How big of an area? Depends on what? Any way to measure and plan for it? Before headsets people used mikes and speakers outside of big equipment, power plants, and along freeways. The headset's advantage is that your ears are always in the center of the interference, and it moves with you when you walk around. * Does anyone know where I could buy the circuitry to do this with mikes and speakers, so I don't have to wear a headset? Or get a schematic to make it? Thanks, Nigel |
#2
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
Nigel wrote: Hi, I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. It works for a headset since the enclosed volume has a predictable soundfield. It can't be done for a room. Get double or triple glazing instead or move. Graham |
#3
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
"Nigel" ** No relation to the famous Doug are you ??? I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. * Does anyone know how effective such a mike/speaker combo could be, given that the interference pattern will be limited to a certain area, and outside of it, there would be less and less interference? How big of an area? Depends on what? ** Totally impossible. Forget it & buy some earplugs. Cotton wool (ie cotton balls) make effective and comfortable ear plugs. ........ Phil |
#4
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
In article .com,
"Nigel" wrote: Hi, I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. * Does anyone know how effective such a mike/speaker combo could be, given that the interference pattern will be limited to a certain area, and outside of it, there would be less and less interference? How big of an area? Depends on what? Any way to measure and plan for it? Before headsets people used mikes and speakers outside of big equipment, power plants, and along freeways. The headset's advantage is that your ears are always in the center of the interference, and it moves with you when you walk around. * Does anyone know where I could buy the circuitry to do this with mikes and speakers, so I don't have to wear a headset? Or get a schematic to make it? Thanks, Nigel Higher frequencies can't be cancelled for a whole room because you'll never get the phase alignment right. You might be able to cancel frequencies below 15 Hz. There's no tone associated with frequencies that low but they can be heard and felt as disturbances. |
#5
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
"Nigel" wrote ...
* Does anyone know where I could buy the circuitry to do this with mikes and speakers, so I don't have to wear a headset? Or get a schematic to make it? The fact that you can't buy something like this for any amount of money should suggest that the technology isn't there (yet?) |
#6
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
On 25 Jul 2006 19:00:51 -0700, "Nigel"
wrote: I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. You MIGHT reduce low frequency stuff a little. No, forget it. Unless you carefully align a system aimed at a fixed position in your apartment, you don't stand a chance. If it's a serious ongoing nuisance, see if you can make them buy you better windows. Otherwise live with it, move or buy earplugs. |
#7
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
Nigel wrote: I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. * Does anyone know how effective such a mike/speaker combo could be, given that the interference pattern will be limited to a certain area, and outside of it, there would be less and less interference? How big of an area? Depends on what? Depends upon frequency and the area you need to cover. The two are intimately related in a way that's simply inextricable. It works really well for headphones because the sensing device, cancelling transducer and the "area" covered, i.e., your ear, are all very close to one another, within an inch or two. That inch or two ofn distance translates directly to a wavelength (actually, it's a fraction of a wavelength, 1/6 wave being about the most, since that's the maximum error in phase that prevents addition rather than cancellation) and that wavelength translates to a maximum frequency where the technique can be expected to work. Assume coverage over a maximum span of 1 inch. That puts a lower limit of coverage to a wabelength of 6 inches. That's a frequency of about 2000 Hz. The cancellation in that small area can be expected to work to an increasing degree the lower in frequency you go below that, and essentially stops working the higher you go above it. Any way to measure and plan for it? Yes, see the general outline of the principle above. Before headsets people used mikes and speakers outside of big equipment, power plants, and along freeways. The headset's advantage is that your ears are always in the center of the interference, and it moves with you when you walk around. More specifically, the advantage is that the area it can correct is VERY limited, i.e., the volume of each cup in the headset. * Does anyone know where I could buy the circuitry to do this with mikes and speakers, so I don't have to wear a headset? Or get a schematic to make it? You want to do it for a room? The same rules of area, wavelength and frequency apply. Assume you want to cover a 12' area. That's a minimum wavelength of 72 feet, which corresponds to an upper effective frequency of about 16 Hz. The conclusion: it won't work for reducing audible noise. In fact, at about half the places in the room, the noise will be the same or louder, as the signal is now reinforced rather than cancelled. In fact, I'd bet there's a chance that the total noise power in the room will remain essentially the same. Get yourselg a sound level meter and a copy of the local noise ordinances. If you find that the sound level exceeds the limits imposed by the ordinance, than check with the local authorites as to the best course of action. While your sound level measurements probably, in and of themselves, have no legal standing, it may be enough to cause a formal review using legally valid measurements and that may lead to an order to limit the noise appropriately. Unfortunately, most statutes aloow for the generation of certain levels of noise that may well be annoying, but are limited to certain times of the day. If the time you're interested in is between. oh, 8:00 AM and 6:00 PM, you're out of luck. But, short of that, and short of ear plugs or ear protectors or your own construction binge, there is no technological solution along the lines you're thinking. |
#8
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
"Nigel" wrote in message
oups.com... Hi, I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. * Does anyone know how effective such a mike/speaker combo could be, given that the interference pattern will be limited to a certain area, and outside of it, there would be less and less interference? How big of an area? Depends on what? Any way to measure and plan for it? Before headsets people used mikes and speakers outside of big equipment, power plants, and along freeways. The headset's advantage is that your ears are always in the center of the interference, and it moves with you when you walk around. * Does anyone know where I could buy the circuitry to do this with mikes and speakers, so I don't have to wear a headset? Or get a schematic to make it? Thanks, Nigel Try this if you have a stereo: Set it to mono or a mono program such as an AM station reverse the wires on one of the speakers so it is out of phase. Be sure the balance control is centered. You should notice weak bass and an odd "feel" to the sound, yet it still seems pretty loud. reverse phasing of one speaker is essentially trying what you want to try. It won't work. It would work somewhat if the speakers were sitting face to face with about 1" gap to let some sound out. With reverse phasing, the output would be down several dbs with lower frequencies. Better to get a sheet of 1/8" plexi (thicker than the typical stuff at the hardware store stocks) and seal it over the window. This drops the noise considerably. John |
#9
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
JohnR66 wrote: Try this if you have a stereo: Set it to mono or a mono program such as an AM station reverse the wires on one of the speakers so it is out of phase. Be sure the balance control is centered. You should notice weak bass and an odd "feel" to the sound, yet it still seems pretty loud. reverse phasing of one speaker is essentially trying what you want to try. It won't work. It would work somewhat if the speakers were sitting face to face with about 1" gap to let some sound out. With reverse phasing, the output would be down several dbs with lower frequencies. Better to get a sheet of 1/8" plexi (thicker than the typical stuff at the hardware store stocks) and seal it over the window. This drops the noise considerably. Lead curtains would work too ! Graham |
#10
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
wrote in message It works really well for headphones because the sensing device, cancelling transducer and the "area" covered, i.e., your ear, are all very close to one another, within an inch or two. That inch or two ofn distance translates directly to a wavelength What are you talking about? The wavelength for an inch is approx 12GHz (12,000,000,000Hz). Around the frequency used for satellite TV broadcasting. Slightly out of your hearing range I should think (sarcastic). (actually, it's a fraction of a wavelength, 1/6 wave being about the most, since that's the maximum error in phase that prevents addition rather than cancellation) and that wavelength translates to a maximum frequency where the technique can be expected to work. Assume coverage over a maximum span of 1 inch. That puts a lower limit of coverage to a wabelength of 6 inches. That's a frequency of about 2000 Hz. A wavelength of 6 inches corresponds to a frequency of around 2GHz. (2000,000,000Hz) Either we are at cross purposes here or you have got it madly. As for noise cancelling. I agree its virtually impossible using speakers due to the complex changes of phase all over the room but who knows, one day with the aid of a computer monitoring multiple mics, comparing it to the unwanted sound from mics outside and feeding multiple speakers, it might be possible. The computer would have to work hard correcting the phase changes constantly changing in the room, but I suspect modern home computers have enough processing power to do that today, but it needs a big demand for noise cancelling, or a good entrepreneur to market it. The easiest way at moment is still decent sound proofing, triple glazing and possibly noise cancelling headphones, but I still find ear plugs give much higher attenuation than noise cancelling headphones. I should know. I live within half a mile of F-15 jets taking off and landing (Lakenheath). I wish you luck as noise has been the bain of my life, but as I am now pushing 50 my hearing is dulling a bit and making life much more pleasant. Regards bucket |
#11
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
On Tue, 1 Aug 2006 15:26:35 +0100, "Bucket"
wrote: wrote in message It works really well for headphones because the sensing device, cancelling transducer and the "area" covered, i.e., your ear, are all very close to one another, within an inch or two. That inch or two ofn distance translates directly to a wavelength What are you talking about? The wavelength for an inch is approx 12GHz (12,000,000,000Hz). Around the frequency used for satellite TV broadcasting. Slightly out of your hearing range I should think (sarcastic). (actually, it's a fraction of a wavelength, 1/6 wave being about the most, since that's the maximum error in phase that prevents addition rather than cancellation) and that wavelength translates to a maximum frequency where the technique can be expected to work. Assume coverage over a maximum span of 1 inch. That puts a lower limit of coverage to a wabelength of 6 inches. That's a frequency of about 2000 Hz. A wavelength of 6 inches corresponds to a frequency of around 2GHz. (2000,000,000Hz) Either we are at cross purposes here or you have got it madly. As for noise cancelling. I agree its virtually impossible using speakers due to the complex changes of phase all over the room but who knows, one day with the aid of a computer monitoring multiple mics, comparing it to the unwanted sound from mics outside and feeding multiple speakers, it might be possible. The computer would have to work hard correcting the phase changes constantly changing in the room, but I suspect modern home computers have enough processing power to do that today, but it needs a big demand for noise cancelling, or a good entrepreneur to market it. The easiest way at moment is still decent sound proofing, triple glazing and possibly noise cancelling headphones, but I still find ear plugs give much higher attenuation than noise cancelling headphones. I should know. I live within half a mile of F-15 jets taking off and landing (Lakenheath). I wish you luck as noise has been the bain of my life, but as I am now pushing 50 my hearing is dulling a bit and making life much more pleasant. Regards bucket You appear to be confusing the speed of sound with the speed of light. Slight error factor present here. For GHz, read kHz and you have it about right. d -- Pearce Consulting http://www.pearce.uk.com |
#12
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
"Bucket" wrote in message ... What are you talking about? The wavelength for an inch is approx 12GHz (12,000,000,000Hz). Around the frequency used for satellite TV broadcasting. Slightly out of your hearing range I should think (sarcastic). A wavelength of 6 inches corresponds to a frequency of around 2GHz. (2000,000,000Hz) Either we are at cross purposes here or you have got it madly. Or you don't know the difference between the speed of sound and the speed of light. MrT. |
#13
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
Kevin McMurtrie wrote: In article .com, "Nigel" wrote: Hi, I am looking for a way to dampen noise from a major, long-term construction site across the street from my apartment by using inverted soundwaves --i.e. mikes pick up the sound, circitry inverts it, speakers send it back out and the interference pattern between the opposite sounds creates relative silence. Numerous companies sell this technology in headset form. Bose, for example. * Does anyone know how effective such a mike/speaker combo could be, given that the interference pattern will be limited to a certain area, and outside of it, there would be less and less interference? How big of an area? Depends on what? Any way to measure and plan for it? Before headsets people used mikes and speakers outside of big equipment, power plants, and along freeways. The headset's advantage is that your ears are always in the center of the interference, and it moves with you when you walk around. * Does anyone know where I could buy the circuitry to do this with mikes and speakers, so I don't have to wear a headset? Or get a schematic to make it? Thanks, Nigel Higher frequencies can't be cancelled for a whole room because you'll never get the phase alignment right. You might be able to cancel frequencies below 15 Hz. There's no tone associated with frequencies that low but they can be heard and felt as disturbances. It takes quite a narrow field to cancel sounds. Reminds me of a current situation I have, not too bad but curious to me. Every once in a while in my home I get a fluttering of a few Hz, less than 10 Hz. Sounds something like a hellicopter, and might very well be one in the area. Its most audible, or should I say feel, in one room only. greg |
#14
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
Bucket wrote: wrote in message It works really well for headphones because the sensing device, cancelling transducer and the "area" covered, i.e., your ear, are all very close to one another, within an inch or two. That inch or two ofn distance translates directly to a wavelength What are you talking about? What we are talking about is the wavelength of SOUND in AIR. Duh. The wavelength for an inch is approx 12GHz (12,000,000,000Hz). Around the frequency used for satellite TV broadcasting. Slightly out of your hearing range I should think (sarcastic). Wrong. WHat do you think the propogation veloxity of SOUND is? 300,000,000 m/s? Check it again, it's about 342m/s. We're talking about SOUND, not LIGHT. (actually, it's a fraction of a wavelength, 1/6 wave being about the most, since that's the maximum error in phase that prevents addition rather than cancellation) and that wavelength translates to a maximum frequency where the technique can be expected to work. Assume coverage over a maximum span of 1 inch. That puts a lower limit of coverage to a wabelength of 6 inches. That's a frequency of about 2000 Hz. A wavelength of 6 inches corresponds to a frequency of around 2GHz. (2000,000,000Hz) Wrong again. Either we are at cross purposes here or you have got it madly. No, you keep making the same fundamental mistake. Please go look up the propogation velocity of SOUND. Please note that the propogation velosity of SOUND is about 1 million times SLOWER than that of LIGHT. Please note the difference between LIGHT and SOUND, most especially it's propogation velocity AND the resulting wavelengths and frequencies. Then, try all your calculation above again, which are off, not suprisingly BY A FACTOR OF 1 MILLION. |
#15
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
No, you keep making the same fundamental mistake. Please go look up the propogation velocity of SOUND. Please note that the propogation velosity of SOUND is about 1 million times SLOWER than that of LIGHT. Please note the difference between LIGHT and SOUND, most especially it's propogation velocity AND the resulting wavelengths and frequencies. Then, try all your calculation above again, which are off, not suprisingly BY A FACTOR OF 1 MILLION. ** What a load of complete crap !! How do you explain Wimbledon then - eh ?? When Roger Federer gives the ball a mighty wack, the "wack" in in time with the picture. Same applies all over the planet. Explain that - go on !!! ......... Phil ;-) |
#16
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
Bucket wrote: As for noise cancelling. I agree its virtually impossible using speakers due to the complex changes of phase all over the room but who knows, one day with the aid of a computer monitoring multiple mics, comparing it to the unwanted sound from mics outside and feeding multiple speakers, it might be possible. Aside from your silly insistance that the speed of propogation of sound is some million times faster than it really is, your assertion here is provably false. It not only might NOT be possible, it IS impossible. As an exterior sound source is some distance away compared to the dimensions of the room, the falloff in SPL as you move about the room will likely be small, simply because the inverse square law makes it so: as the difference in distance between the nearest and furthest point in the room from the external source is small, the difference in sound level will be small as well. Say the external sound source is 200 ft away, moving 10 feet one way or the othere in the room is changing the distance to that source by only 5%, with a resulting SPL change on the order of maybe 1dB The same inverse square law relationship bites you for the local speakers: here, the relative differences are large. Move that same 10 feet, from 2 feet to 12 feet, say, and the SPL differences are huge, in this example, on the order of 31 dB. From the viewpoint of amplitude alone, you're screwed. And from a phase viewpoint, multiple speakers make it much worse. One speaker might be able to fully compensate at exactly 1 point in space. Now add more than one, and what got cancelled by one speaker at one point is now going to get filled in by the second "cancelling" speaker whose phase and amplitude are now wrong for that point. Your technique suffers from all the same problems that a single-speaker technique, and would, in fact, do an overall POORER job. Now, add to that the fact that essentially you're dealing with what's called a non-staionary signal. The technique of single source/speaker cancellation works when the time delay between the two remains constant. if it does not, for any reason, then the cancellation fails. The reasons time delays can change is because either the source OR the subject has moved or is moving (remember, it only provably works at one point in space: it make work at others, but you don't have a choice of where those points are AND multiple speakers reduces the number from provably one to provably none). And since the propogation velocity of sound which is, we are reminded: 342 meters per second and NOT, as someone suggested 300,000,000 meters per second (because we are talking about SOUND, mechanically propogates through AIR, governed by the rules of thermodynamics and NOT electromagnetics) is, in fact, variable, then the delay time can change on its own. For example, the velocity of propogation of SOUND in AIR goes as a function of the square root of the absolute temperature of said AIR. Further, it is at every instance the velocity propogation relative to the bulk velocity of the AIR through which it is propogating, and does NOT remain constant relative to the source or destination points. That means that thermal currents and wind can change the delay time significantly. That is not going to have much an effect for sound produced close to the listener, but can have a significant effect over several hundred feet. This problem is very significant, for example, when attempting to measured the acoustical properties of large enclosed spaces, like cathedrals. The computer would have to work hard correcting the phase changes constantly changing in the room, No, the computer would have to violate acoustical physics. Even Bill Gates wouldn't dare try to pull taht one off, though they might advertise it anyway. but I suspect modern home computers have enough processing power to do that today, but it needs a big demand for noise cancelling, The market demands for noise cancellation are well large enough to inspire a number of companies top have commercial solutions for it, all constrained by physics. That's why their done with cancellation closely proximal to either the sound source, in the case of examples like actively suppressed mufflers, or the listening position, in the case of noise cancelling headphones. or a good entrepreneur to market it. Entrepeneurs are known for their proclivity to ignore physical reality. They're immune to the consequences: it's the investors that pay the inevitable price. The easiest way at moment is still decent sound proofing, triple glazing and possibly noise cancelling headphones, but I still find ear plugs give much higher attenuation than noise cancelling headphones. I should know. With the same certaity that you "know" the frequency of a sound whose wavelength is 1" is in the GHz range? I live within half a mile of F-15 jets taking off and landing Yeah, noise cancelling headphone must not work well at all. That's why the pilots of the same F15's use them. |
#17
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
On Wed, 2 Aug 2006 01:55:36 +1000, "Phil Allison"
wrote: Please note the difference between LIGHT and SOUND, most especially it's propogation velocity AND the resulting wavelengths and frequencies. Then, try all your calculation above again, which are off, not suprisingly BY A FACTOR OF 1 MILLION. ** What a load of complete crap !! How do you explain Wimbledon then - eh ?? When Roger Federer gives the ball a mighty wack, the "wack" in in time with the picture. Same applies all over the planet. Explain that - go on !!! |
#18
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
On Wed, 2 Aug 2006 01:55:36 +1000, "Phil Allison"
wrote: How do you explain Wimbledon then - eh ?? When Roger Federer gives the ball a mighty wack, the "wack" in in time with the picture. Are you drunk, Phil? You know quite well, if viewed from any distance, the wack is perceptibly NOT in time with the visual. If you want a more dramatic example, think thunder and lightning. |
#19
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
Thanks everyone for your lively and interesting discussion. Clearly it
won't work for noise without headphones. But there is also going to be a lot of blindingly bright arc welding while they are building the gigantic tennis stadium across from my apartment. Could I make a pair of glasses that beam out the opposite light that's coming in? That would be within an inch of my eyes. Nigel |
#20
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
"Nigel" wrote in message oups.com... Thanks everyone for your lively and interesting discussion. Clearly it won't work for noise without headphones. But there is also going to be a lot of blindingly bright arc welding while they are building the gigantic tennis stadium across from my apartment. Could I make a pair of glasses that beam out the opposite light that's coming in? That would be within an inch of my eyes. Windowshades. Sunglasses. |
#21
Posted to rec.audio.tech
|
|||
|
|||
Noise canceling via soundwave inversion without headphones?
"Nigel" writes:
Thanks everyone for your lively and interesting discussion. Clearly it won't work for noise without headphones. But there is also going to be a lot of blindingly bright arc welding while they are building the gigantic tennis stadium across from my apartment. Could I make a pair of glasses that beam out the opposite light that's coming in? That would be within an inch of my eyes. What a great idea! You could use them to see during an atomic bomb blast as well! -- % Randy Yates % "My Shangri-la has gone away, fading like %% Fuquay-Varina, NC % the Beatles on 'Hey Jude'" %%% 919-577-9882 % %%%% % 'Shangri-La', *A New World Record*, ELO http://home.earthlink.net/~yatescr |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Note to Trevor | Audio Opinions | |||
Artists cut out the record biz | Pro Audio |