Intelligibility of interrupted speech

Miller and Licklider (J. Acoust. Soc. Am. 22: 167-173,1950)  investigated the effects of replacing portions of CVC
syllables with silence. Their results showed that periodic interruption of speech (50% on/off cycle) resulted only in a
small decline in intelligibility if the rate of interruption was between about 10-100 Hz. Intelligibility suffered when the
interruption rate was low (<2 Hz), presumably because entire syllables and/or phonemes were replaced by silence.
Performance also declined with higher interruption rates (>200 Hz) where subjects reported a noisy quality, as though
an additional sound source had been superimposed.

The effects of speech interruption are illustrated with audio examples below. The first example is of a male voice
saying "The watchdog gave a warning growl." This is followed by several processed versions in which 50%
of the speech waveform is replaced by silence. This was achieved by multiplying the digital signal with a
square wave window function alternating between 0 and 1. The audio examples illustrate interruption rates of
1, 2, 4, 8, 16, 32, 64, 128, 256, and 512 Hz. The figure shows the waveform of the sentence processed
with a 1-Hz interruption rate. 

           .WAV format                           .AU format

  1. Original sentence                                    Original sentence
  2. 1 Hz interruption rate                              1 Hz interruption rate  (see figure)
  3. 2 Hz interruption rate                              2 Hz interruption rate
  4. 4 Hz interruption rate                              4 Hz interruption rate
  5. 8 Hz interruption rate                              8 Hz interruption rate
  6. 16 Hz interruption rate                           16 Hz interruption rate
  7. 32 Hz interruption rate                           32 Hz interruption rate
  8. 64 Hz interruption rate                           64 Hz interruption rate
  9. 128 Hz interruption rate                         128 Hz interruption rate
  10. 256 Hz interruption rate                         256 Hz interruption rate
  11. 512 Hz interruption rate                         512 Hz interruption rate

 

   

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