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Why are the bass notes of a car radio heard by people on the street an

  1. May 25, 2013 #1
    1. The problem statement, all variables and given/known data

    Why are the bass notes of a car radio heard by people on the street and not the high notes


    3. The attempt at a solution

    I think it has something to do with fixed and free end boundaries and may have something do with the fact that the high notes are being reflected back into the car while the bass notes are transmitted through the car. I have not learnt the pitch or acoustics unit yet. Can anyone help?
     
  2. jcsd
  3. May 25, 2013 #2

    nsaspook

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    With all things being equal on a perfect transducer reflection,absorption and (room) modes do affect what's heard on the outside of a car from a single speaker isolated from the car body but mainly (rant mode) it's because they have 500W+ amplifiers with low-pass filters to restrict the signal to below a few hundred cycles , the speakers connected those large amplifers can only respond to those low frequency signals and are usually bolted to the cars body. There is some interaction with modes causing large peaks in the frequency response of the cars interior but it's mainly bass range brute power vs normal levels of high note power you are hearing.
    http://www.physicsclassroom.com/Class/sound/u11l3d.cfm

    Here are some car freq response charts for a 2008 Honda sub upgrade. http://www.flickr.com/photos/nsaspook/sets/72157621840211633/

    As you can see the speakers are usually mounted in doors or large panels forming an enclosure with external surface areas that transmit low frequencies easily to the outside as speakers produce sound on BOTH sides of the cone coupling bass to the outside. Most of the higher frequency sound waves are reflected inside the enclosure instead of being transmitted outside.
     
    Last edited: May 25, 2013
  4. May 25, 2013 #3

    CWatters

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    Windows/glass also attenuates high frequencies more than low frequencies...

    Google found..
    sound+reduction+chart.png
     
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