Volume 115, Issue 5, May 2004
Index of content:
- PSYCHOLOGICAL ACOUSTICS 
115(2004); http://dx.doi.org/10.1121/1.1691036View Description Hide Description
This study examines whether a temporal masking effect may be consistent with a decrease in gain at the masker frequency during the course of the masker. Threshold level of a long-duration notched-noise masker needed to mask a 1- or 4-kHz signal was measured for three conditions: a short-duration signal with a short delay or a long delay from masker onset, and a long-duration signal. The difference between threshold for the long-delay signal and the short-delay signal was defined as the temporal effect. The size of the temporal effect depended on signal frequency, signal level, and masker notch width. Filters estimated from the data had narrower bandwidths for the long-delay condition than for the short-delay condition or the long-duration condition, which seems inconsistent with the hypothesis of a decrease in gain. However, modeling of the data in terms of basilar-membrane input–output functions is consistent with a decrease in gain in the masker frequency region during the course of the masker. For a notch width of 0.0 the results are consistent with a decrease in gain at the signal frequency. For a relative notch width of 0.4, the decrease in gain at the masker frequency may cause a decrease in the suppression of the signal. This decrease in suppression could explain the decrease in filter bandwidth with signal delay.
Effect of number of masking talkers and auditory priming on informational masking in speech recognition115(2004); http://dx.doi.org/10.1121/1.1689343View Description Hide Description
Three experiments investigated factors that influence the creation of and release from informational masking in speech recognition. The target stimuli were nonsense sentences spoken by a female talker. In experiment 1 the masker was a mixture of three, four, six, or ten female talkers, all reciting similar nonsense sentences. Listeners’ recognition performance was measured with both target and masker presented from a front loudspeaker (F–F) or with a masker presented from two loudspeakers, with the right leading the front by 4 ms (F–RF). In the latter condition the target and masker appear to be from different locations. This aids recognition performance for one- and two-talker maskers, but not for noise. As the number of masking talkers increased to ten, the improvement in the F–RF condition diminished, but did not disappear. The second experiment investigated whether hearing a preview (prime) of the target sentence before it was presented in masking improved recognition for the last key word, which was not included in the prime. Marked improvements occurred only for the F–F condition with two-talker masking, not for continuous noise or F–RF two-talker masking. The third experiment found that the benefit of priming in the F–F condition was maintained if the prime sentence was spoken by a different talker or even if it was printed and read silently. These results suggest that informational masking can be overcome by factors that improve listeners’ auditory attention toward the target.
Dominance of missing fundamental versus spectrally cued pitch: Individual differences for complex tones with unresolved harmonics115(2004); http://dx.doi.org/10.1121/1.1690076View Description Hide Description
In a two-alternative, forced-choice experiment, subjects had to compare the pitches of two sounds, A and B. Each sound was composed of four successive harmonics of a fundamental frequency between 100 to 250 Hz, added in cosine or Schröder phase. The harmonic frequencies of A were lower than those of B; the missing fundamental frequency of A was higher than that of B. The dominance of the missing fundamental versus the spectrally cued pitch—a pitch percept corresponding to spectral components—was measured as a function of the lowest harmonic in A. The pitch percept is dominated by the missing fundamental if the harmonics are resolved If the harmonics become unresolved and are added in Schröder phase, the dominance shifts to a spectrally cued pitch 75% of the subjects). In the cosine phase condition, many subjects could detect the fundamental pitch well into the unresolved harmonic range For others, the transition was in the realm of partly resolved harmonics. This shows that the temporal envelope modulation of stimuli with only four unresolved harmonics can give a relatively clear fundamental pitch percept. However, this percept varies considerably among subjects.