[Nigel]

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

[Eeyore]

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

[Phil Allison]

"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

[Kevin McMurtrie]

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.

[Richard Crowley]

"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?)

[Laurence Payne]

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.

[[email protected]]

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.

[JohnR66]

"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

[Eeyore]

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

[Bucket]

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

[Don Pearce]

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

[Mr.T]

"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.

[[email protected]]

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

[[email protected]]

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.

[Phil Allison]

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 ;-)

[[email protected]]

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.

[Laurence Payne]

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 !!!

[Laurence Payne]

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.

[Nigel]

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

[Richard Crowley]

"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.

[Randy Yates]

"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