No description available.

No description available.

No description available.

No description available.

Eight experiments were performed to investigate factors affecting the discrimination of two characteristics of very brief tones. The subjects (adults with normal hearing) were asked to rate targets that differed either by amplitude envelope or by a change in frequency. For the majority of the trials, a target was followed (after a brief silent interval) by a pure tone referred to as a "mask". Two factors affecting discrimination within this simple paradigm were examined in detail; the frequency separation and the duration of the silent interval between the target and the mask. For most of the other conditions, a target and mask were embedded in a series of sounds that were presented with an isochronous rhythm. Several features of these "background" sounds were varied across the experiments, including their timbre, presentation rate and frequency relationships with the target and mask. / Superior discrimination was obtained when targets were able to perceptually "emerge" from a background of tones or noises. Specifically, performance was strongest when a target was easily segregated from the other sounds in the series by timing factors or through having a unique frequency. Discrimination was also enhanced when the interfering effects of the mask were removed through association with other tones in the sequence. The data suggest that a simple "interruption" model of processing, in which the presence of a mask disrupts subjects' ability to process individual characteristics of a target, does not adequately explain the differences in discrimination observed across the conditions. A more comprehensive explanation could consider attentional factors that may influence subjects' ability to accurately identify which tone in a sequence is to be rated. However, a perspective based on auditory segregation seems to most consistently explain the data; individual characteristics of a target were most easily discriminated when the target was perceived as belonging outside of an auditory group formed by the background sounds. This was especially true when the mask was likely to have been perceived as belonging within the group due to frequency proximity and/or rhythmic regularity.

Eight experiments examined the effects of placing a sequential organization cue (the frequency proximity between successive tones) into competition with various binaural cues. The sequential organization of an alternating pair of monaural pure tones (A and B) was found to oppose the effect of a contralateral noise burst (synchronous with B) to delateralize B's perceived position and to distort its perceived purity. Similarly, the sequential organization of a monaural tone with the same-ear component of a dichotic tone was found to often oppose the perceptual integration of the components of the dichotic tone. These findings were interpreted as suggesting that sequential cues compete with certain binaural cues during lateralization and dichotic integration decisions. However, sequential cues were found not to influence the fusion of identical sinusoids presented at opposite ears. Thus, binaural fusion appeared to occur independently of sequential organization processes. These findings were discussed in terms of levels and mechanisms of processing, and of ecological demands.

No description available.

No description available.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.