JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
    The difference of sound levels between two points is\[40\,\,dB\]. What is the ratio of pressure amplitudes between the two points?

    A) \[10\]                                   

    B) \[200\]

    C)  \[100\]                                

    D)  \[400\]

    Correct Answer: C

    Solution :

    Let          \[{{L}_{1}}=10\log \left( \frac{{{I}_{1}}}{{{I}_{0}}} \right)\] and        \[{{L}_{2}}=10\log \left( \frac{{{I}_{2}}}{{{I}_{0}}} \right)\] Therefore, difference of sound levels                 \[\Delta L={{L}_{2}}-{{L}_{1}}=10\log \left( \frac{{{I}_{2}}}{{{I}_{1}}} \right)\] Now,\[40=10\log \left( \frac{{{I}_{2}}}{{{I}_{1}}} \right)=20\log \left( \frac{{{P}_{2}}}{{{P}_{1}}} \right)\]\[[\because \,\,I\propto {{P}^{2}}]\] or            \[\frac{40}{20}=\log \left( \frac{{{P}_{2}}}{{{P}_{1}}} \right)or\frac{{{P}_{2}}}{{{P}_{1}}}={{(10)}^{2}}=100\]


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