Turn Your House Into Noise Cancellation Headphones

There is some otherwise nice real estate at the end of Navy runways,
neighborhoods in San Diego and Virginia Beach where pilots practice
taking off an aircraft carrier with after burners wide open.

A lot of residents would be willing to pay $5,000 or more to be able
to talk to other people in a room at the flip of a switch.  If it
draws a lot of power or when there is little outdoor noise it might be
desirable to turn it off or have it automatically turn off after 5
minutes and then back on as soon as the noise exceeds a threshold.

Noise cancellation should be cheaper than redoing the walls and in
some ways it might be an easier problem than headphones where the
distances involved are only a cm.

A few noisy zones might be tolerable as long as the locations of quiet
zones in a room could be moved and adjusted.


Bret Cahill

In comp.dsp Bret Cahill <Bret_E_Cahill@yahoo.com> wrote:

> There is some otherwise nice real estate at the end of Navy runways,
> neighborhoods in San Diego and Virginia Beach where pilots practice
> taking off an aircraft carrier with after burners wide open.

> A lot of residents would be willing to pay $5,000 or more to be able
> to talk to other people in a room at the flip of a switch.  If it
> draws a lot of power or when there is little outdoor noise it might be
> desirable to turn it off or have it automatically turn off after 5
> minutes and then back on as soon as the noise exceeds a threshold.

I have heard of using triple pane windows to reduce noise near
freeways.  That might not be enough for jet fighters, though.

> Noise cancellation should be cheaper than redoing the walls and in
> some ways it might be an easier problem than headphones where the
> distances involved are only a cm.

But the (wall) area is larger.  I believe that takes drivers
(speakers) distributed along the walls, spaced depending on
the frequencies that need canceling and the amount of cancelation
required.   But $5000 is a small part of the price of most houses,
so you could probably go somewhat more. 

And, you could also use it as a sound system at the same time!

Extra DSP challenge, it has to send the right signal to each speaker
such that a reasonable stereo image is formed.

> A few noisy zones might be tolerable as long as the locations of quiet
> zones in a room could be moved and adjusted.

Have a computer follow each person around and adjust the cancelation
for those positions in the room where people are.

I have also heard about active concert hall reflection control
systems that make halls that are acoustically larger than the
actual size, or otherwise improve the acoustics.  It seems that
the problems could be related.


-- glen

"Bret Cahill" <Bret_E_Cahill@yahoo.com> wrote in message 
news:6a20c7cf-42b5-42b2-93cb-e7d0773ffd4b@n12g2000yqh.googlegroups.com...
> There is some otherwise nice real estate at the end of Navy runways,
> neighborhoods in San Diego and Virginia Beach where pilots practice
> taking off an aircraft carrier with after burners wide open.
>
> A lot of residents would be willing to pay $5,000 or more to be able
> to talk to other people in a room at the flip of a switch.  If it
> draws a lot of power or when there is little outdoor noise it might be
> desirable to turn it off or have it automatically turn off after 5
> minutes and then back on as soon as the noise exceeds a threshold.
>
> Noise cancellation should be cheaper than redoing the walls and in
> some ways it might be an easier problem than headphones where the
> distances involved are only a cm.
>

Noise cancelling headphones largely work because:

a) the distances involved are only a cm. The headphone speaker subtracts the 
ambient noise from the signal. The distance from speaker to eardrum must be 
much less than the wavelength of the sound for this to work (or else the 
phase will be out). As the distance increases, the lowest frequency that can 
cancelled decreases, making them increasingly less effective.

b) The microphone which detects ambient is acoustically isolated from the 
speaker such that feedback doesn't occur. This is easy with headphones, will 
be very problematic with regular speakers.




> A few noisy zones might be tolerable as long as the locations of quiet
> zones in a room could be moved and adjusted.
>
>
> Bret Cahill
>
>
>
>
>
>
>
> 

In sci.physics Peter Webb <webbfamily@optusnetdiespamdie.com.au> wrote:
> 
> "Bret Cahill" <Bret_E_Cahill@yahoo.com> wrote in message 
> news:6a20c7cf-42b5-42b2-93cb-e7d0773ffd4b@n12g2000yqh.googlegroups.com...
>> There is some otherwise nice real estate at the end of Navy runways,
>> neighborhoods in San Diego and Virginia Beach where pilots practice
>> taking off an aircraft carrier with after burners wide open.
>>
>> A lot of residents would be willing to pay $5,000 or more to be able
>> to talk to other people in a room at the flip of a switch.  If it
>> draws a lot of power or when there is little outdoor noise it might be
>> desirable to turn it off or have it automatically turn off after 5
>> minutes and then back on as soon as the noise exceeds a threshold.
>>
>> Noise cancellation should be cheaper than redoing the walls and in
>> some ways it might be an easier problem than headphones where the
>> distances involved are only a cm.
>>
> 
> Noise cancelling headphones largely work because:
> 
> a) the distances involved are only a cm. The headphone speaker subtracts the 
> ambient noise from the signal. The distance from speaker to eardrum must be 
> much less than the wavelength of the sound for this to work (or else the 
> phase will be out). As the distance increases, the lowest frequency that can 
> cancelled decreases, making them increasingly less effective.
> 
> b) The microphone which detects ambient is acoustically isolated from the 
> speaker such that feedback doesn't occur. This is easy with headphones, will 
> be very problematic with regular speakers.

Also they do nothing for the "felt" noise in a high noise environment.
 
One would be better off in checking on rebates for noise reduction
modifications which are often available for those living near airports but
seldom publicized.


-- 
Jim Pennino

Remove .spam.sux to reply.

In comp.dsp Peter Webb <webbfamily@optusnetdiespamdie.com.au> wrote:
(snip)
>> There is some otherwise nice real estate at the end of Navy runways,
>> neighborhoods in San Diego and Virginia Beach where pilots practice
>> taking off an aircraft carrier with after burners wide open.

>> A lot of residents would be willing to pay $5,000 or more to be able
>> to talk to other people in a room at the flip of a switch.  

(snip)
> Noise cancelling headphones largely work because:

> a) the distances involved are only a cm. The headphone speaker 
> subtracts the ambient noise from the signal. The distance from 
> speaker to eardrum must be much less than the wavelength of the 
> sound for this to work (or else the phase will be out). 

I believe that isn't quite right.  If you have a whole wall full
of canceling speakers, it should still be able to work.
But yes, one will only work over distances somewhat shorter
than one wavelength.

> As the distance increases, the lowest frequency that can 
> cancelled decreases, making them increasingly less effective.

> b) The microphone which detects ambient is acoustically isolated 
> from the speaker such that feedback doesn't occur. This is easy 
> with headphones, will be very problematic with regular speakers.

I don't believe that this is true for headphones.  As far as
I understand it, they have to correct for, and subtract, the
feedback.  

-- glen

On 15/09/2011 03:14, Peter Webb wrote:
>
> "Bret Cahill" <Bret_E_Cahill@yahoo.com> wrote in message
> news:6a20c7cf-42b5-42b2-93cb-e7d0773ffd4b@n12g2000yqh.googlegroups.com...
>> There is some otherwise nice real estate at the end of Navy runways,
>> neighborhoods in San Diego and Virginia Beach where pilots practice
>> taking off an aircraft carrier with after burners wide open.
>>
>> A lot of residents would be willing to pay $5,000 or more to be able
>> to talk to other people in a room at the flip of a switch. If it
>> draws a lot of power or when there is little outdoor noise it might be
>> desirable to turn it off or have it automatically turn off after 5
>> minutes and then back on as soon as the noise exceeds a threshold.
>>
>> Noise cancellation should be cheaper than redoing the walls and in
>> some ways it might be an easier problem than headphones where the
>> distances involved are only a cm.
>>
>
> Noise cancelling headphones largely work because:
>
> a) the distances involved are only a cm. The headphone speaker subtracts
> the ambient noise from the signal. The distance from speaker to eardrum
> must be much less than the wavelength of the sound for this to work (or
> else the phase will be out). As the distance increases, the lowest
> frequency that can cancelled decreases, making them increasingly less
> effective.
>
> b) The microphone which detects ambient is acoustically isolated from
> the speaker such that feedback doesn't occur. This is easy with
> headphones, will be very problematic with regular speakers.

c) It's hard to make destructive interference occur everywhere in a 
large volume.

Consider..If you have three people in a room you need to create 
destructive interference in six places (each ear) and they are moving 
virtually independantly. Can't imagine how it can be done without 
headphones.

Bret Cahill wrote:

> There is some otherwise nice real estate at the end of Navy runways,
> neighborhoods in San Diego and Virginia Beach where pilots practice
> taking off an aircraft carrier with after burners wide open.
> 
> A lot of residents would be willing to pay $5,000 or more to be able
> to talk to other people in a room at the flip of a switch. 

If residents are willing to pay that kind of cash to lower the ambient noise 
levels in their homes then all they need to do is soundproof them.  
Insulating the walls does just that and it also brings the added benefit of 
reducing the energy spent in HVAC.  Adding sound reflection panels also 
helps, with the added benefit of being able to provide some shade.  None of 
these technologies require an increase in energy spending.


Rui Maciel

> >> There is some otherwise nice real estate at the end of Navy runways,
> >> neighborhoods in San Diego and Virginia Beach where pilots practice
> >> taking off an aircraft carrier with after burners wide open.
>
> >> A lot of residents would be willing to pay $5,000 or more to be able
> >> to talk to other people in a room at the flip of a switch. If it
> >> draws a lot of power or when there is little outdoor noise it might be
> >> desirable to turn it off or have it automatically turn off after 5
> >> minutes and then back on as soon as the noise exceeds a threshold.
>
> >> Noise cancellation should be cheaper than redoing the walls and in
> >> some ways it might be an easier problem than headphones where the
> >> distances involved are only a cm.
>
> > Noise cancelling headphones largely work because:
>
> > a) the distances involved are only a cm. The headphone speaker subtracts
> > the ambient noise from the signal. The distance from speaker to eardrum
> > must be much less than the wavelength of the sound for this to work (or
> > else the phase will be out). As the distance increases, the lowest
> > frequency that can cancelled decreases, making them increasingly less
> > effective.
>
> > b) The microphone which detects ambient is acoustically isolated from
> > the speaker such that feedback doesn't occur. This is easy with
> > headphones, will be very problematic with regular speakers.
>
> c) It's hard to make destructive interference occur everywhere in a
> large volume.

It need not be everywhere or even most areas of the room.

> Consider..If you have three people in a room you need to create
> destructive interference in six places (each ear) and they are moving
> virtually independantly. Can't imagine how it can be done without
> headphones.

The system could monitor the location of the head of each person in
the room.  GPS isn't quite there yet so it must be done locally, with
sonar or radar using a target much less cumbersome than headphones,
i.e., an ear ring, cap or necklace.

The signals from the speakers would be coordinated to eliminate just
the noise in a small 0.03 m^3 volume around each head.

This approach requires a more sophistication in the design but would
greatly reduce the cost and power and the number and/or size of the
speakers for the production run.


Bret Cahill

On 9/15/2011 11:45 AM, Bret Cahill wrote:
>>>> There is some otherwise nice real estate at the end of Navy runways,
>>>> neighborhoods in San Diego and Virginia Beach where pilots practice
>>>> taking off an aircraft carrier with after burners wide open.
>>
>>>> A lot of residents would be willing to pay $5,000 or more to be able
>>>> to talk to other people in a room at the flip of a switch. If it
>>>> draws a lot of power or when there is little outdoor noise it might be
>>>> desirable to turn it off or have it automatically turn off after 5
>>>> minutes and then back on as soon as the noise exceeds a threshold.
>>
>>>> Noise cancellation should be cheaper than redoing the walls and in
>>>> some ways it might be an easier problem than headphones where the
>>>> distances involved are only a cm.
>>
>>> Noise cancelling headphones largely work because:
>>
>>> a) the distances involved are only a cm. The headphone speaker subtracts
>>> the ambient noise from the signal. The distance from speaker to eardrum
>>> must be much less than the wavelength of the sound for this to work (or
>>> else the phase will be out). As the distance increases, the lowest
>>> frequency that can cancelled decreases, making them increasingly less
>>> effective.
>>
>>> b) The microphone which detects ambient is acoustically isolated from
>>> the speaker such that feedback doesn't occur. This is easy with
>>> headphones, will be very problematic with regular speakers.
>>
>> c) It's hard to make destructive interference occur everywhere in a
>> large volume.
>
> It need not be everywhere or even most areas of the room.

It needs to be done for each ear separately, for all individuals in the 
room as they move around. The cancelling signal for one ear must not add 
to the noise at another. I don't see it happening.

>> Consider..If you have three people in a room you need to create
>> destructive interference in six places (each ear) and they are moving
>> virtually independantly. Can't imagine how it can be done without
>> headphones.
>
> The system could monitor the location of the head of each person in
> the room.  GPS isn't quite there yet so it must be done locally, with
> sonar or radar using a target much less cumbersome than headphones,
> i.e., an ear ring, cap or necklace.
>
> The signals from the speakers would be coordinated to eliminate just
> the noise in a small 0.03 m^3 volume around each head.

Around each _ear_ simultaneously.

> This approach requires a more sophistication in the design but would
> greatly reduce the cost and power and the number and/or size of the
> speakers for the production run.

What production run?

If you could do this, you could also build a system that allowed you to 
listen to a symphony, while the person sitting at the other end of a 
couch heard rock and roll. I doubt it!

Jerry
-- 
Engineering is the art of making what you want from things you can get.

On Sep 15, 4:45&#4294967295;pm, Bret Cahill <Bret_E_Cah...@yahoo.com> wrote:
> > >> There is some otherwise nice real estate at the end of Navy runways,
> > >> neighborhoods in San Diego and Virginia Beach where pilots practice
> > >> taking off an aircraft carrier with after burners wide open.
>
> > >> A lot of residents would be willing to pay $5,000 or more to be able
> > >> to talk to other people in a room at the flip of a switch. If it
> > >> draws a lot of power or when there is little outdoor noise it might be
> > >> desirable to turn it off or have it automatically turn off after 5
> > >> minutes and then back on as soon as the noise exceeds a threshold.
>
> > >> Noise cancellation should be cheaper than redoing the walls and in
> > >> some ways it might be an easier problem than headphones where the
> > >> distances involved are only a cm.
>
> > > Noise cancelling headphones largely work because:
>
> > > a) the distances involved are only a cm. The headphone speaker subtracts
> > > the ambient noise from the signal. The distance from speaker to eardrum
> > > must be much less than the wavelength of the sound for this to work (or
> > > else the phase will be out). As the distance increases, the lowest
> > > frequency that can cancelled decreases, making them increasingly less
> > > effective.
>
> > > b) The microphone which detects ambient is acoustically isolated from
> > > the speaker such that feedback doesn't occur. This is easy with
> > > headphones, will be very problematic with regular speakers.
>
> > c) It's hard to make destructive interference occur everywhere in a
> > large volume.
>
> It need not be everywhere or even most areas of the room.
>
> > Consider..If you have three people in a room you need to create
> > destructive interference in six places (each ear) and they are moving
> > virtually independantly. Can't imagine how it can be done without
> > headphones.
>
> The system could monitor the location of the head of each person in
> the room. &#4294967295;GPS isn't quite there yet so it must be done locally, with
> sonar or radar using a target much less cumbersome than headphones,
> i.e., an ear ring, cap or necklace.
>
> The signals from the speakers would be coordinated to eliminate just
> the noise in a small 0.03 m^3 volume around each head.
>
> This approach requires a more sophistication in the design but would
> greatly reduce the cost and power and the number and/or size of the
> speakers for the production run.
>
> Bret Cahill- Hide quoted text -
>
> - Show quoted text -

Active "wallpaper" with hundreds or even thousands of small speakers
in a massive array with precise multiple beamforming capability should
be able to do the job.  I wouldn't be surprised if this hasn't already
been done in military projects to acoustically cloak submarines/boat
hulls.