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Sine Sweep Measurement Procedure

  1. Generate the sine sweeps using generate_sinesweeps.m.
  2. Open the pd patch sinesweeps.pd, in pd.
  3. Ensure that the patch is not in editing mode, and check the ``compute audio'' box in the main pd window.
  4. Adjust the ``Output Volume'' so that when you click on ``Record Response To The Sine Sweeps,'' the system under test is behaving linearly (i.e. not clipping), but so that the input signal to the sound interface is not too noisy.
  5. If there is an input volume on the sound interface, adjust it so that the levels approximately match those shown in Figure 12 when you click on ``Record Response To The Sine Sweeps.'' If the sound interface has no input volume, then you will need to adjust the ``Output Volume'' accordingly.

    Figure 12: sinesweeps.pd after making a measurement with an appropriate input level
    \resizebox{4in}{!}{\includegraphics{\figdir /sinesweepsScale.eps}}

  6. Once you are satisfied with the results, click the ``Write Responses to Disk'' button.
  7. pd will write the file Resp.wav to disk. Rename this file so that the name matches the measurement you just made. For instance, you might rename it to nonlinear2Resp.wav if it corresponded to the second time you measured the transfer function of a weakly nonlinear system.
  8. Run sinesweeps_response('nonlinear2, 100, 0.4') in MATLAB or Octave to analyze the measured response. This means that the inverse filter will be restricted to a dynamic range of 100 (40 dB), which helps avoid exaggerating problems beneath $\omega_1$ and above $\omega_2$, where the excitation signal has little energy. 0.4 refers to the length in seconds of the linear impulse response term to be extracted. Plots will be generated, and the file nonlinear2ImpResp.wav will be written to disk.

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Download imp_meas.pdf

``Transfer Function Measurement Toolbox'', by Edgar J. Berdahl and Julius O. Smith III,
REALSIMPLE Project — work supported by the Wallenberg Global Learning Network .
Released 2008-06-05 under the Creative Commons License (Attribution 2.5), by Edgar J. Berdahl and Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University