"Picket Fence" effect

Miller and Licklider (J. Acoust. Soc. Am. 22: 167-173,1950) combined interrupted speech and interrupted
noise maskers to create an interesting effect they described as the "picket fence" effect. In this situation,
speech and noise are temporally interleaved to form a continuous signal. They reported that perceived
continuity of the speech signal was increased by this manipulation, although intelligibility was unaffected.
Bashford, Reiner and Warren (Percept. Psychophys. 51: 211-217,1992) have found that the addition of
noise to fill the silent gaps can improve intelligibity if the stimuli are complete sentences, rather than isolated
monosyllables as used by Miller and Licklider.

The picket fence effect is illustrated with audio examples below. The first example is of a male voice
saying "The watchdog gave a warning growl" in quiet. This is followed by several processed versions
in which 50% of the speech waveform is alternated with white noise at a signal-to-noise ratio of 0 dB.
The audio examples illustrate speech-noise alternation at 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 alternation 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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      School of Human Development
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