what this sound could be?

[woshixiaozhu]

Hi, sorry for my stupid question.. I noticed that on youtube's many wrc onboard video, the rally cars especially focus/c4 in recent years seem to produce a squealing, very high pitch sound constantly(though it seems to be changing a little bit as the car speeds up/down). It is some sound like a water is boiled in a kettle with a whistle.... for example

http://www.youtube.com/watch?v=WM0s_2pTQM0


one can clearly hear the sound. Can anyone tell me the source of this sound? I am really curious... Thank you. :)

[6789]

Its audio interference from the car, thats as far as I know

[Koz]

It's the turbo.

[Mirek]

It's the turbo.

No, this sound is quite common also in on onboards where there is no turbo. It's really some audio interference.

Here You have same interference in S1600: http://www.mediasport.cz/rally-cz/video/10_jeseniky_dohnal_rz6.html

[darkstar]

yes, in my opinion it is because sometimes the sound is directly taken from the intercom. the wining sound is just the electrical fluctuation produced by the generator(i guess).

have a look at this onboard, here´s the sound taken from the intercom(i know because i know the driver) and you hear the wining sound:

http://www.youtube.com/watch?v=HFcNtX_0hMM

here the same driver, but sound is not taken from the intercom:

http://www.youtube.com/watch?v=JkOkOcCQetE

both cars are naturally aspirated of course ;)

[woshixiaozhu]

Thank you guys your explanations are really helpful :) Thank you

[Koz]

No, this sound is quite common also in on onboards where there is no turbo. It's really some audio interference.

Here You have same interference in S1600: http://www.mediasport.cz/rally-cz/video/10_jeseniky_dohnal_rz6.html

Learning something new every day :p

[Allar]

what's this whistle sound on barkeing?

http://www.youtube.com/watch?v=VWs5vn3xAzA

[Steve Boyd]

I don't think the whistling is the alternator. They've had alternators since the 70's & the noise only started when electronic management systems were introduced. My road going Toyota Corolla AE86 GT used to do the same thing through the radio/cassette player if you turned the volume up with a tape paused in the player. The pitch seemed to be related to engine rpm and the volume related to throttle opening so I'm going for electrical interference from the feed to the injectors.

The chirping noise is from the turbo when the throttle is suddenly closed.

[darkstar]

I don't think the whistling is the alternator. They've had alternators since the 70's & the noise only started when electronic management systems were introduced. My road going Toyota Corolla AE86 GT used to do the same thing through the radio/cassette player if you turned the volume up with a tape paused in the player. The pitch seemed to be related to engine rpm and the volume related to throttle opening so I'm going for electrical interference from the feed to the injectors.

The chirping noise is from the turbo when the throttle is suddenly closed.

yes, with this casette thing your right, noticed this too(maybe its when you get ground directly from the carbody?). but what finally causes the interference i´m not sure about, maybe you´re right here too, but did corolla ae 86 have injectors already?

and with that chirping sound you´re also right afaik...

[Steve Boyd]

Yes the Corolla had electronic fuel injection and the engine management control box was located under the dash not far from the radio. It would be interesting to compare a sound track recorded from the intercom of a car running carbs to back up the theory.