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NVH problem

  1. Mar 25, 2010 #1
    please help me to solve this problem

    Figure shows noise results for a prototype van measured on a rolling road. the vehicle had a four cylinder in line engine. the engine speed was varied in 3rd gear from just above stall to about 4500 rpm. the sound pressure at the representative interior position was measured in dB using standard reference, namely 20 micro Pa. figure shows the overall noise level and also the component associated with second harmonic of the engine speed.

    1. the noise peak at 3600 rpm is due to an acoustic resonance with a stand ing wave between the floor and roof of the van. what is the frequency of this resonance and what is the vertical dimension of the van interior.
    2.sketch a graph of the microphone signal at 3600 rpm. (it should include the time and sound pressure axes )
    3. comment on the overall results in the figure indicating if they are acceptable or if they indicate a specific NVH problem.

    http://img25.imageshack.us/img25/5412/p25031015160001.jpg [Broken]
    Last edited by a moderator: May 4, 2017
  2. jcsd
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