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Wave interference in a car at speed

  1. Sep 27, 2010 #1
    I'm trying to figure out the interaction between the stereo of a car and the wind/road noise coming from outside.

    I was debating with someone about the interaction and argued that the stereo sounded diminished in volume level because of destructive interference. But I honestly don't know whether that's correct or a load of bull.

    Where are my acoustic engineers at?
  2. jcsd
  3. Sep 28, 2010 #2
    The sound from the wind and road outside is random. For destructive interference to even have a chance to occur you would need this source to be coherent. It isn't.
    The reason the stereo sounds diminished is more to do with the way your ear/brain adjusts to the prevailing sound intensity.
    A good experiment to try is to adjust the base and treble to your liking when the car is moving and there's plenty of noise. (Be careful - keep you eye on the road!).
    Then, next day, when you first get in the car and switch on the stereo before you switch on the engine, listen to the bass and treble levels. You will find them much higher than you imagined.
  4. Sep 28, 2010 #3
    With AM radio you do get volume changes as you drive along due to interference from other waves/weather patterns. You shouldn't experience this with FM radio though.

    The wind and road noise wont change any signal coming from your radio speakers, just the way your ears hear it. As Stonebridge says, it's the reason why a radio that doesn't seem loud after motorway driving is deafening when you first turn it on in the morning.
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