Strange, long wooooo sound at steady speeds, ICE on

[wb8nbs]

FYI apparently Wizzurp has found a solution:

http://fordcmaxhybridforum.com/topic/6669-how-to-quick-and-easy-reversible-anc-delete/

 

I pulled the connector he shows but my C-Max doesn't make the noise much in the summer.

[jestevens]

Sometimes I drive with the windows down and hear this noise, probably not describing it right but to me it sounds to me like a particular exhaust note..like how they tune the exhaust sound of the Mustang.  I don't think it's intentional, probably irritates the ANC in just the right way at a certain RPM with the windows down, etc.  I have heard it inside the car with the windows up too when ICE comes on within certain RPM range.  I just take it to be part of the way the car works.

 

Maybe it just seem annoying because the car is otherwise so quiet, still not as annoying as wind buffeting noise, and no where as annoying as that rental car I drove with the 4 cylinder engine mated to a CVT that kept pretending to make noises like it was "shifting" - that thing had as much noise and vibration as a prop plane..spoiled from driving hybrids.

[wb8nbs]

FYI apparently Wizzurp has found a solution:

http://fordcmaxhybridforum.com/topic/6669-how-to-quick-and-easy-reversible-anc-delete/

 

I pulled the connector he shows but my C-Max doesn't make the noise much in the summer.

It's now January and I haven't heard a peep out of the ANC system. Disconnecting the microphones totally worked!

 

I am POed at Ford for not seeing this. It's clear to me that NO ONE at Ford actually knows how the noise cancelling system works. A moot point now that the C-Max has been orphaned.

[fbov]

FWIW, no wooooo from my ANC for several years now. It was always intermittent, not showing until a trip to Vermont for Thanksgiving 2013. Then it became persistent, say once a month in winter, now gone?

 

Here's a thought. The root cause is a chassis/frame/drive train resonance that's been in cars for years, but which no one noticed as long as engine speed is constantly changing. I grew up driving a clutch, so I always listen to an automatic's shift points. My wife's Hyundai hybrid is a 6-speed. Driving a C-Max, the biggest difference initially was the lack of engine speed changes. I'm now comfortable with a car driven by a "stationary engine" designed to run a constant RPM. 

 

Designing loudspeakers, you quickly learn that resonances are a lot easier to hear than drop-outs; peaks stick out more than dips. You don't need much energy to excite them, and once they start buzzing, you can't miss it. I once measured a box with a resonance in the mid 400 Hz range, "middle A". Never heard it, except when using a frequency generator to zero in on the exact frequency!

 

Ford didn't have the luxury of only suppressing musical notes. They had a broadband source that would continuously change base frequency by a factor of 6, and stay there for a while. The driver can easily run the engine at the exact speed needed to excite any resonance. That's a tough thing to counteract. Ford did a pretty good job in my book. 

 

And the wooooo is now gone because the chassis has aged and I do have one case of very hard braking on rough road that would have loosened things up. If yours still wooooo's and you haven't pulled the mic, maybe try looking for a bumpy road?

 

Have fun,

Frank

Edited January 16, 2019 by fbov