Date of Award

Fall 1979

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Electrical and Computer Engineering

First Advisor

Niederjohn, Russell J.

Second Advisor

Jeutter, Dean C.

Third Advisor

Moeller, Arthur C.


Enhancement of the intelligibility of speech in noise is a complex and unsolved problem. In order to gain some understanding of the speech in noise situation, the relative importance of various frequency ranges to the intelligibility of speech in noise is investigated in this thesis. Some conclusions which are drawn for the frequency range and S/N ratios used include: l) No high- pass or low-pass filter increases the intelligibility of speech in noise. 2) Speech can be low-pass or high-pass filtered at 2500Hz without significant loss of intelligibility. 3) The intelligibility of speech decreases rapidly with increasing high-pass filter cutoff frequency. 4) With speech in noise, listeners tend to set the level of the composite signal based upon the level of the speech, regardless of the S/N ratio. The Articulation Index is calculated and validated for the experimental data gathered in this work.



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