The present study investigated the combination tone 2fl-f2 in normal hearing subjects and subjects with high frequency noise-induced hearing loss by measuring the forward masking effect of 2fl-f2 exerted at its own frequency. Forward masking was plotted as the increase in masked threshold of a brief probe tone located at frequency 2fl-f2 as a function of the intensity of the primary tones, fl and f2. The masking effect of the lower primary alone, fl, was also measured to determine the possible contribution of fl toward the total masking obtained with the fl+f2 stimulus. Results of this investigation showed that 1) a forward-masking effect attributable to 2fl-f2 was seen for each normal-hearing subject, usually beginning at an fl+f2 intensity between 40 and 60 dB SPL. Average slopes of the growth of this masking were 0.8 between 60 and 70 dB SPL and 1.1 between 70 and 80 dB SPL. 2) there was little or no masking effect due to fl+f2 for hearing-loss subjects at intensities between 60 and 70 dB SPL, most likely explained by the fact that the quiet thresholds at the fl, f2, and probe tone frequencies were elevated for these subjects. This finding agreed with published studies by showing that the forward masking effect was strongly and inversely correlated with the quiet thresholds at the fl, f2, and probe tone frequencies (significant to p=.0l). 3) at an fl+f2 intensity of 80 dB SPL, several hearing-loss subjects displayed a masking effect attributable to 2fl-f2. It is not clear why this occurred for some of these subjects, because even at 80 dB SPL, the sensation level of the fl+f2 stimulus was only slightly supra-threshold. 4) for some normal-hearing and hearing-loss subjects a significant masking effect due to fl alone was noted. This finding made it difficult to assess the contribution of 2fl-f2 toward the total masking displayed with the fl+f2 stimulus for these subjects. 5) results with the fl and fl+f2 stimulus were highly variable for both subject groups. 6) the unresolved role of suppression in distortion product generation as well as a limited understanding of noise-induced hearing loss make it difficult to apply the present results toward one particular model of combination tone production. / Medicine, Faculty of / Audiology and Speech Sciences, School of / Graduate

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Nine experiments were done to test three theories of auditory stream segregation and to investigate some conditions under which segregated tones re-integrate. In two-part trials, subjects (adults with normal hearing) first heard a segregation-inducing "Induction Sequence" whose effects upon an immediately subsequent "Test Sequence" were measured. The Test Sequence always had tones that alternated rhythmically between two frequencies. Rhythm and total duration of Induction Sequence tones were varied in the first two studies. Similarity of Induction and Test Sequences aided segregation whereas rhythmic predictability and longer tone durations in the Induction Sequence did not. Frequency alternation during the Induction Sequence was not necessary to induce segregation in the Test Sequence. The effects of sudden and gradual changes in lateralization, spatial location and sound level were investigated also. The data suggest that explaining segregation by peripheral processes is inadequate and that, once a distinct percept emerges from an auditory scene, properties derived from the percept (particularly changes) are fed back to control the ongoing analysis of that scene. A neural adaptation to stimuli with constant properties may form part of this analysis.

It is generally recognized that simple harmonic ratios among partials promote their perceptual fusion. However, the influence of parallel gliding in log frequency upon fusion is not understood. The present experiment investigated fusion in relation to different types of parallel and non-parallel log-frequency motion of three concurrent tonal glides. The main hypothesis was that parallel motion on log-frequency-by-time coordinates favors fusion. It was reasoned that a higher degree of fusion of the glides evokes fewer auditory images. Fusion was thus measured by asking eighteen subjects to rate the number of distinct sounds perceived in various gliding stimuli. On test trials, subjects received a pair of stimuli in succession and had to judge which one contained more sounds and to rate the size of the difference on a 7-point scale. Each stimulus was a complex of three sinusoidal tones, gliding in frequency. Each 1400-ms three-glide complex was either increasing or decreasing in frequency, and the spacing among its components was either small, medium or large. The stimuli were aligned in one of five ways: (1) harmonically related, parallel, and therefore unequally spaced in log frequency, (2) inharmonic, parallel, and equally spaced in log frequency, (3) inharmonic, parallel, and unequally spaced in log frequency, (4) non-parallel and diverging in log frequency, and (5) non-parallel and converging in log frequency. Results showed that more sources were perceived under the three parallel conditions than under the two non-parallel ones (p $<$ 0.00001). Moreover, as the spacing between gliding partials increased, more distinct sounds were heard (p $<$ 0.00001). These results suggest that both spectral spacing and non-parallel log-frequency motion segregate concurrent glides. A multiple regression analysis showed that parallel log-frequency gliding promotes fusion over and above the contribution of average spectral spacing and harmonicity (p $<$.0001). The observed dat

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Thesis (Master)--İzmir Institute of Technology, İzmir, 2005. / Keywords: Product design, sound quality, emotion design, emotional branding. Includes bibliographical references (leaves. 111-122).

Thesis (B.Sc)--University of Hong Kong, 2005. / "A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, June 30, 2005." Also available in print.