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Transfer Functions

A transfer function is a total measurement of the amplitude and phase response of an audio device.  

A key part of an accurate transfer function is the removal of the input test signal response from the final measurement.  This is done by passing a sample of the input signal to the second channel of the analyzer and removing its response from the response of the device under test. 



You should use logarithmic amplitude scaling; subtracting two logarithmic quantities equates to division of their ratio values.

Key Settings:
Mode:      Real-Time
Views:      Spectrum, Phase
Sampling Rate:     At least twice the highest frequency produced by the device under test
FFT size:      4096 typical
Averaging:      4
Peak Hold:      Off
Smoothing Window:    Hanning
Dual Channel Spectral Processing:   Real Transfer Function Left/Right"
Sampling Format:    16 bit Stereo
Frequency scaling:     your choice
Amplitude scaling:     Logarithmic
Spectral Weighting:     flat
   
Procedure:
  • Connect a noise generator to the input of the device under test.
  • Connect the output of the device under test to the Left input channel of the analyzer.
  • Connect same signal generator to the Right input channel of the analyzer.
  • Run the analyzer until the average spectrum response settles to a consistent level.


    Interpretation:
    The spectrum display contains the amplitude response of the device and the phase display contains the phase response.