[HUMOR?] "Madison Ave" meets DSP

On 4/24/2016 7:07 AM, radams2000@gmail.com wrote:
> The marketing department may have mangled the language, but generating anti-noise through the audio speakers is now common , even in low-end cars. It allows them to remove a lot of heavy sound-dampening materials, so they get slightly better mpg (and it's cheaper, the speakers are already there, you just need to add DSP mips ).
> Personally I'm uncomfortable knowing that if I cut my speaker wires, my car will sound like a tin can.

How much of this do you know for a fact?  So the car stereo is on all 
the time the engine is running?  Or turning off the stereo makes your 
vehicle noisy?

-- 

Rick

Yes I know this for a fact and have worked on various algorithms for that m=
arket.=20
Yes the anti-noise is on all the time. It's mostly effective below 200hz or=
 so.=20
The most common approach synthesizes sine waves based on tachometer pulses =
and adjusts the amplitude and phase of each harmonic to achieve a null. The=
re are one or more error microphones in the roof liner to generate an error=
 signal that drives the additive algorithm.=20

More advanced algorithms use a signal from an accelerometer mounted in the =
engine compartment as the reference signal, and use some form of the FXLMS =
algorithm to generate the anti-noise.=20

There are many real-world complications, and everyone who naively ventures =
into this area is pretty humble after a year or so of trying to achieve goo=
d results.=20

Bob