Miller and Licklider (J. Acoust. Soc. Am. 22: 167-173,1950)
also investigated the effect an interrupted noise masker
on the intelligibility of CVC syllables. Their results showed that
periodic interruption of the masker (50% on/off cycle)
produced a release from masking. The greatest release from masking
was found for rates of interruption between about
20-200 Hz.
The effects of interrupted white-noise maskers is illustrated with the
examples below. The first example is of
a male voice saying "The watchdog gave a warning growl," mixed with
white noise at a signal-to-noise ratio
of 0 dB. This is followed by versions of the sentence mixed with interrupted
maskers with a 50% on/off cycle
for different rates of interruption. This was achieved by multiplying
the digital waveform of the noise masker
with a square wave window function alternating between 0 and 1 before
mixing with the speech, as shown in
the figure below. The audio examples illustrate interruption rates
of 1, 2, 4, 8, 16, 32, 64, 128, 256, and 512 Hz.
Email:
assmann@utdallas.edu
School of Human Development
The University of Texas at Dallas, Richardson,
Texas, 75083, USA
Tel: (214) 883-2435
FAX: (214) 883-2491