1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Acoustic input impedance at ear entrance based on frequency and termination impedance

  1. Jan 2, 2013 #1
    1. The problem statement, all variables and given/known data
    The context of this question is that it is the first question on a post grad paper in transducers and sound reinforcement. We've been looking at using electrical circuits to model acoustical and mechanical systems, and also using two-port analysis.

    I need to create a model of a tube/ear canal using MATLAB, with facility to change the termination impedance to any known value. Termination is the ear drum and the acoustic input impedance is what I need to calculate/plot.
    Info I have is that the ear canal can be assumed to be 30mm long, and as a first approximation may be considered as a cylindrical tube with a rigid termination. To start with I'm going to consider low frequencies only - allowing the lumped parameter model to be used, i.e. assume to reflections at openings.

    2. Relevant equations
    I need to know whether to use two-port analysis, or a mobility analog or impedance analog, and also whether changing the termination impedance means that the termination is no longer rigid.


    3. The attempt at a solution
    I tried using two-port analysis - using x=0 is the ear drum and x=-L is the opening. The matrix I used led to this result - (cos(k*L)+((1i*rho_0*c)/Z_0).*sin(k*L))./...
    ((1i/rho_0*c).*sin(k*L)+(1/Z_0)*cos(k*L));
    which I've tried entering into MATLAB, but the results don't seem to make sense. For a start I know that the complex element of Z_neg_L should only be positive, and that it should not be at zero for so much of the time because when imag(Z_neg_L) is at zero that signifies resonance.

    Any help would be greatly appreciated.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?



Similar Discussions: Acoustic input impedance at ear entrance based on frequency and termination impedance
  1. Impedence Matching (Replies: 0)

  2. Impedance Problem (Replies: 0)

Loading...