Unmasking for Pure Tones and Spondees: Interaural Phase and Time Disparities Interference with the binaural intelligibility of spondee words and the binaural detection of a sinusoid of continuously varying frequency (250 to 4000 Hz) produced by two continuous independent random noise signals, N1 and N2, was measured in 10 normal-hearing adults at three masker levels under five conditions of listening: ... Research Article
Research Article  |   December 01, 1968
Unmasking for Pure Tones and Spondees: Interaural Phase and Time Disparities
 
Author Affiliations & Notes
  • Raymond Carhart
    Northwestern University, Evanston, Illinois
  • Tom W. Tillman
    Northwestern University, Evanston, Illinois
  • Peter J. Dallos
    Northwestern University, Evanston, Illinois
Article Information
Research Articles
Research Article   |   December 01, 1968
Unmasking for Pure Tones and Spondees: Interaural Phase and Time Disparities
Journal of Speech, Language, and Hearing Research, December 1968, Vol. 11, 722-734. doi:10.1044/jshr.1104.722
History: Received April 1, 1968
 
Journal of Speech, Language, and Hearing Research, December 1968, Vol. 11, 722-734. doi:10.1044/jshr.1104.722
History: Received April 1, 1968

Interference with the binaural intelligibility of spondee words and the binaural detection of a sinusoid of continuously varying frequency (250 to 4000 Hz) produced by two continuous independent random noise signals, N1 and N2, was measured in 10 normal-hearing adults at three masker levels under five conditions of listening:

  1. homophasic (N10N20S0);

  2. parallel antiphasic (N1π N2π S0);

  3. opposed antiphasic (N1π N2−π S0);

  4. parallel time delay (N10.8N20.8S0);

  5. opposed time delay (N10.8N2−0.8S0).

The two antiphasic conditions produced equivalent masking-level differences (MLDs) for spondee words (5.3 dB re homophasic level). The MLDs for the two time-delay conditions (t = 0.8 msec) were also approximately equal, but were appreciably smaller (3.8 dB). For pure-tone signals, averaged MLDs were also less for time-delayed than for antiphasic listening, but the four nonhomophasic conditions yielded functions relating MLD to frequency that had a common pattern. MLDs increased with frequency between 250 and 400 Hz, were maximal in the range between 400 and 800 Hz, and then declined to very small but fairly uniform values above 1200 Hz. A comparison of the MLDs yielded for pure tones with those for spondees supports the conclusion that MLDs for spondees are mediated by the release from masking that occurs for the spectral components involved in spondee reception at threshold level.

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