Coherence Function from Spectral Analysis - Signal Processing of Random Physiological Signals - page 212

3. correlation among sources,

4. input-output time-delay errors,

5. input measurement noise,

6. input-output nonlinearities,

7. input-output feedback,

8. reverberation effects, and

9. common source periodicities.

18.6 CONCLUSION
The coherence function, like many of the other mathematical operations used in signal
processing, is susceptible to abuses by researchers who intentionally misapply its use
or is not well informed with regard to its limitations. The coherence function should
be used to establish a relationship between input and output of a system. None of the
literature supports the idea of using the coherence function to compare two output
signals such as the electromyograms (EMG) from two different muscles. Finally, as in all
types of scientific tools, all assumptions must be met if the results are to be interpreted
correctly.

18.7 REFERENCES

1. Bendat, J. S. and Piersol, A. G. Random Data: Analysis and Measurement Procedures .

Wiley Interscience, 1971.

2. Bendat, J. S. “Statistical Errors in Measurement of the Coherence Function and

Input-Output Quantities,” Journal of Sound and Vibration , September 1978.

3. Lessard, C. S. “Analysis of Nystagmus Response to Pseudorandom Velocity Input,”

Compute Methods and Programs in Biomedicine , Vol. 23, 1986.

4. Neter, J., Wasserman, W., and Hunter M.H., Applied Linear Regression Models. Irwin,

1983.