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Old 20th May 2009, 17:36   #16
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Originally Posted by CrackedHead View Post
To ask a very basic question - how does noise cancellation technology identify what "niose" needs to be canceled out?

After all - these cars (ones that currently come with noise cancellation) do have ICE setups (and pardon me for comparing ICE to noise). So the system would identify what's noise (engine noise, tyre noise) and only cancel those.

I'm having trouble relating an 18 wheeler's horn with these other noise sources.
Well engine noise and such is a continous tone while the horn is an impulse. In the old days (when music was sold on LPs and EPs) we used to use an electronic tick and pop reducer to reduce the ticks and pops that occures on LPs. I assume in todays world with DSP technonology they could easily identify the horn from the engine and eliminate the engine.

However think, how often do you change gear looking at your tachometer? - mostly your ears are your tach.

Eliminating all noise (even if we have algoritims to recognise the horn from the engine) in a car IS and always will be detremental to competent driving.
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Old 20th May 2009, 17:52   #17
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Eliminating all noise (even if we have algoritims to recognise the horn from the engine) in a car IS and always will be detremental to competent driving.
Agreed, but still do we have a ready solution to acheive may be 70-80%?
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Old 20th May 2009, 19:20   #18
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Originally Posted by navin View Post
However think, how often do you change gear looking at your tachometer? - mostly your ears are your tach.

Eliminating all noise (even if we have algoritims to recognise the horn from the engine) in a car IS and always will be detremental to competent driving.
I agree that the lack of auditory feedback (e.g. tyres squealing when you turn too fast) are an important part of driving(and the joy of it).

But then - what an individual wants from the car is something subjective. Some who is chauffeured around or wants to enjoy the ICE would probably like such a feature.
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Old 20th May 2009, 20:28   #19
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The solution has been around for the last 30 or more years, but I doubt if a practical one exists commercially (outside of products like noise-canceling headphones etc., i.e. embedded in products).

The solution, in principle, is as simple as what the gurus have said for missing bass: check if one of the speakers are wired with wrong polarity, resulting in phase and anti-phase waves meeting each other and canceling out. The earliest implementation I have seen was in 1982 for an open-top Standard Herald by a gentleman who headed DEBEL (Defence Electronics and Bio Engineering Labs, Bangalore) - of course he wanted to reduce exhaust noise (after silencer).

The noise reduction efficiency is anyhow <50-70% because of various factors.
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Old 20th May 2009, 21:25   #20
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Lol, everyone's gone technical on this and here I am stuck in the real world "its possible" thinking. I'm a die hard DIY and aesthetic influenced mods fan, so i wouldn't ask the thread starter to give up!

Yes, everyone has spoken about the perils of complete noise cancellation and what not, but I'm under the impression that whats achievable can be in line with a Luxury Car, S-class and Lexus LS for example. Who's to say that we cannot achive the feeling of "calmness" felt in these cars and it cannot be duplicated in a Palio or NHC.
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Old 21st May 2009, 00:37   #21
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but when i spoke about this Accord's system, i only meant mild noises that emanate from the engine bay, like the drone from the engine and tyre roar.
road noise is cut out by a small percentage, but nothing that can suppress horns or other noises we are supposed to hear.
hope that clears it..
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Old 21st May 2009, 01:16   #22
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Quote:
Originally Posted by panky12345 View Post
Agreed, but still do we have a ready solution to acheive may be 70-80%?
I think you can achieve it with damping

1. Engine: damping engine firewall
2. tyres: damping wheel wells, floor.
3. and damp rest of the body for wind noise.

this will still leave you enough to recognise the sounds you need while driving. you can't damp glass parts

Navin, any product I can try for engine firewall damping in US? I see you referred to heatlon in the other thread but google doesn't come up with much info on that.
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Old 21st May 2009, 07:22   #23
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you can't damp glass parts .
But how about double glazed glass ? Wouldn't that help in reducing the noise a wee bit .

Also how about filling the doors with some kind of hard foam (like the one used for insulating external AC ducts).Agreed the door would get heavy and the hinges would need bolstering , but we are discussing noise reduction as the priority.

I still feel that panel gaps is the number one target area.Apart from wheel wells and underbody that need to be targeted as you've suggested.

Last edited by absynthguzzler : 21st May 2009 at 07:23.
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Old 21st May 2009, 10:10   #24
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A lot of the cars employ underbody and floor and roof mats which cancel noise. the panel gaps can be checked by using a heavier grade rubber beading and deploying it right around the door. blinds are a way to reduce noise from windows atleast in the rear since they cannot be employed up front. some of the vibes can be reduced by employing rubber bushing on undercapsiaie parts that rattle and can be tied or bolted down. even the fabrics used in seats make an awful lot of difference.
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Old 21st May 2009, 13:35   #25
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Quote:
Originally Posted by absynthguzzler View Post
Lol, everyone's gone technical on this ... Who's to say that we cannot achive the feeling of "calmness" felt in these cars and it cannot be duplicated in a Palio or NHC.
Quote:
Originally Posted by frankmehta View Post
... but nothing that can suppress horns or other noises we are supposed to hear ...
Quote:
Originally Posted by vivekiny2k View Post
I think you can achieve it with damping ...
Quote:
Originally Posted by absynthguzzler View Post
But how about double glazed glass ? ...
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Originally Posted by valhallen.282 View Post
A lot of the cars employ underbody and floor and roof mats which cancel noise. ...
A ha, fundamental confusion!

Noise Cancellation is the subject of *active cancellation* - producing an anti-phase wave so that the undesirable waves are canceled out. This technique needs a (powered) device for generating the anti-phase wave. Noise-cancelling headphones use this,

Noise Suppression, on the other hand, is about *passive suppression" - preventing the offending waves from permeating / being generated inside the car by damping, sealing etc. This technique dissipates the energy of the wave by mechanical means.

As @panky-bhai had referred to "dead silence that one experiences with noise-cancellation headphones", and also because the thead title said "noise cancellation", is leading some to go 'technical'. IMHO, we should stick to the subject.

Damping and how else to achieve mechanical noise suppression has already been discussed in the Damping Materials thread.
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Old 21st May 2009, 15:14   #26
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Quote:
Originally Posted by CrackedHead View Post
Some who is chauffeured around or wants to enjoy the ICE would probably like such a feature.
I use a .22 and a pair of Sennheissers. :-)

Quote:
Originally Posted by frankmehta View Post
but nothing that can suppress horns or other noises we are supposed to hear.
hope that clears it..
There is technology available to do this, the question is: is it safe to do so?

Quote:
Originally Posted by vivekiny2k View Post
Navin, any product I can try for engine firewall damping in US?
What I used to do (when I was in the US) was strip the firewall out of the car and FRP the inner wall (the wall on the cabin side). 2 layers of FRP (about 3mm) helped a lot.
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Old 21st May 2009, 17:24   #27
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.. ok keeping aside the 'technical discussions', can a desi jugaad be done?

SAM, LBM.. where are you guys?
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Old 21st May 2009, 17:45   #28
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Well there is a fundamental difference between active noise cancellation in HEADPHONES like the Bose QC3, and trying to implement the same in a car, which is a 3-D space.

In normal headphones, the ear canal is assumed to be a 1-D path, which means that the noise picked up by the mics placed on the headphones can be canceled relatively easily. All you need to do is to invert the signal and play it back through the drivers. As the noise and the signal produced by the speaker have just one path to travel to the eardrum, the noise cancellation works well.

In a 3-D space, on the other hand, the noise and the produced signal would have different path lengths for EVERY point in the car. So one speaker wouldn't suffice. You'd need multiple microphones and multiple speakers to have some semblance of a noise cancellation effect. Theoretically, you'd need way more speakers than you could even begin to comprehend to achieve perfect noise cancellation.

Achieving noise cancellation in 2-D is hard enough. Don't even try the same in 3-D.

And a 'desi jugaad' is out of the question, IMHO. Would need dedicated signal processing circuitry and lots of equipment to even try.
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Old 22nd May 2009, 12:01   #29
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Not that this is related but it after reading experiences like these I seem to be hardening to the view that after a certain level the pursuit of perfect sound in car audio is quite futile.

There are so many tradeoffs required to reproduce music in a car that it will never be even remotely close to the high standards of home system. I still love music in a car, but I accept the default system in much the same way a teenager accepts the sound of an MP3 player to fill the void of empty silence.
- John Krutke (Zaph|Audio)
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Old 22nd May 2009, 12:14   #30
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Long ago emergency services in the U.S had raised their voice against making the car cabin noiseless.

I had a Honda Prelude which had the active noise cancellation long ago (since it was a experimentation vehicle for Honda). But then, it was just part of ICE I think. Accord's is to remove the engine drone or boom when it switches to fewer cylinders.

I don't know of any active noise cancellation which is generic for all noise.
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