Biomedical subjects

R W Hukin

Publications and source records attributed to R W Hukin.

8 recordsLinked to original sources

PubMed2004

Limits to the role of a common fundamental frequency in the fusion of two sounds with different spatial cues.

Two experiments establish constraints on the ability of a common fundamental frequency (F0) to perceptually fuse low-pass filtered and complementary high-pass filtered speech presented to different ears. In experiment 1 the filter cut-off is set at 1 kHz. When the filters are sharp, giving little overlap in frequency between the two sounds, listeners report hearing two sounds even when the sounds at the two ears are on the same F0. Shallower filters give more fusion. In experiment 2, the filters' cut-off frequency is varied together with their slope. Fusion becomes more frequent when the signals at the two ears share low-frequency components. This constraint mirrors the natural filtering by head-shadow of sound sources presented to one side. The mechanisms underlying perceptual fusion may thus be similar to those underlying auditory localization.

Acoustic Stimulation↗

PubMed2000

Effectiveness of spatial cues, prosody, and talker characteristics in selective attention.

The three experiments reported here compare the effectiveness of natural prosodic and vocal-tract size cues at overcoming spatial cues in selective attention. Listeners heard two simultaneous sentences and decided which of two simultaneous target words came from the attended sentence. Experiment 1 used sentences that had natural differences in pitch and in level caused by a change in the location of the main sentence stress. The sentences' pitch contours were moved apart or together in order to separate out effects due to pitch and those due to other prosodic factors such as intensity. Both pitch and the other prosodic factors had an influence on which target word was reported, but the effects were not strong enough to override the spatial difference produced by an interaural time difference of +/- 91 microseconds. In experiment 2, a large (+/- 15%) difference in apparent vocal-tract size between the speakers of the two sentences had an additional and strong effect, which, in conjunction with the original prosodic differences overrode an interaural time difference of +/- 181 microseconds. Experiment 3 showed that vocal-tract size differences of +/- 4% or less had no detectable effect. Overall, the results show that prosodic and vocal-tract size cues can override spatial cues in determining which target word belongs in an attended sentence.

Adult↗

PubMed2000

Effects of reverberation on spatial, prosodic, and vocal-tract size cues to selective attention.

Three experiments explored the resistance to simulated reverberation of various cues for selective attention. Listeners decided which of two simultaneous target words belonged to an attended rather than to a simultaneous unattended sentence. Attended and unattended sentences were spatially separated using interaural time differences (ITDs) of 0, +/-45, +/-91 or +/-181 micros. Experiment 1 used sentences resynthesized on a monotone, with sentence pairs having F0 differences of 0, 1, 2, or 4 semitones. Listeners' weak preference for the target word with the same monotonous F0 as the attended sentence was eliminated by reverberation. Experiment 1 also showed that listeners' ability to use ITD differences was seriously impaired by reverberation although some ability remained for the longest ITD tested. In experiment 2 the sentences were spoken with natural prosody, with sentence stress in different places in the attended and unattended sentences. The overall F0 of each sentence was shifted by a constant amount on a log scale to bring the F0 trajectories of the target words either closer together or further apart. These prosodic manipulations were generally more resistant to reverberation than were the ITD differences. In experiment 3, adding a large difference in vocal-tract size (+/- 15%) to the prosodic cues produced a high level of performance which was very resistant to reverberation. The experiments show that the natural prosody and vocal-tract size differences between talkers that were used retain their efficacy in helping selective attention under conditions of reverberation better than do interaural time differences.

Attention↗

PubMed1999

Auditory objects of attention: the role of interaural time differences.

The role of interaural time difference (ITD) in perceptual grouping and selective attention was explored in 3 experiments. Experiment 1 showed that listeners can use small differences in ITD between 2 sentences to say which of 2 short, constant target words was part of the attended sentence, in the absence of talker or fundamental frequency differences. Experiments 2 and 3 showed that listeners do not explicitly track components that share a common ITD. Their inability to segregate a harmonic from a target vowel by a difference in ITD was not substantially changed by the vowel being placed in a sentence context, where the sentence shared the same ITD as the rest of the vowel. The results indicate that in following a particular auditory sound source over time, listeners attend to perceived auditory objects at particular azimuthal positions rather than attend explicitly to those frequency components that share a common ITD.

Adult↗

PubMed1998

Perceptual segregation of a harmonic from a vowel by interaural time difference in conjunction with mistuning and onset asynchrony.

The two experiments reported here examine how an inter-aural time difference (ITD) interacts with two other cues, mistuning and onset asynchrony, in reducing the contribution of a single frequency component to the perception of a vowel's identity. Previous experiments have shown that although ITD is generally rather ineffective at segregating a simultaneous harmonic frequency component from a vowel, it can produce some segregation when listeners have already been exposed to the isolated segregated component. A difference in ITD increases segregation overall in experiment 1 where the to-be-segregated component can also have a different onset time from the remainder of the vowel, and experiment 2 shows a similar result when the to-be-segregated component is mistuned. However, segregation by ITD is present just as strongly on trials when there is neither mistuning nor a difference in onset-time as on trials where these additional cues are present. Segregation on trials when there is neither mistuning nor a difference in onset-time is however larger in the present experiment which mixed all conditions together than in similar trials in an earlier experiment that had a blocked design [C.J. Darwin and R.W. Hukin, J. Acoust. Soc. Am. 102, 2316-2324 (1997)]. The results show that segregation by ITD increases when other more potent cues are present in the experiment.

Humans↗

PubMed1997

Perceptual segregation of a harmonic from a vowel by interaural time difference and frequency proximity.

The five experiments reported here examine the conditions under which sounds differing in their interaural time difference (ITD) are segregated for the purposes of perceiving a vowel's identity. Experiment 1 confirms previous findings that (i) a difference in ITD provides only a very weak cue for segregating a vowel's 500-Hz harmonic from the remainder of an isolated vowel; (ii) embedding the harmonic in a series of 500-Hz tones produces some segregation, which is enhanced if the harmonic and the tones differ in ITD from the rest of the vowel; and (iii) when these latter sounds are presented in the same block as isolated vowels, they facilitate segregation of the harmonic by ITD in the isolated vowels. The subsequent experiments show that this last effect, across-trial facilitation, is only produced by sounds which cue both the frequency and the ITD of the harmonic; either alone is insufficient. We also show that: (i) a single cue tone at the frequency of the harmonic is sufficient to facilitate the use of ITD in grouping; (ii) sequential organization by frequency proximity dominates over sequential organization by ITD when simultaneous sound sources are present; and (iii) the effectiveness of a cue tone can be abolished by capturing it into a synchronous harmonic complex. The experiments clarify the conditions under which ITDs contribute to the segregation of simultaneous sounds.

Auditory Threshold↗

PubMed1995

Grouping in pitch perception: evidence for sequential constraints.

Evidence is presented that sequential auditory grouping constraints apply to the perception of pitch. Experiment 1 shows that the pitch changes produced by mistuning the fourth harmonic of a 90-ms 12-harmonic 155-Hz fundamental complex tone are substantially reduced when the complex is preceded by four 90-ms tones at the same frequency as the mistuned component. Both the pitch changes and their reduction by the tonal sequence precursor remain when the mistuned component and the precursor are presented contralateral to the remaining components. Experiment 2 shows that reducing the level of the same mistuned component reduces the size of the pitch change, but only if the mistuned component is presented ipsilaterally. To the extent that adaptation can be equated with a physical reduction in level, this result provides further evidence against peripheral adaptation playing a significant role in the auditory grouping of harmonics in pitch perception.

Functional Laterality↗

PubMed1995

Comparison of the effect of onset asynchrony on auditory grouping in pitch matching and vowel identification.

Previous experiments have shown that when a slightly mistuned harmonic of a complex tone starts more than about 80 msec before the remaining components, it makes a reduced contribution to the pitch of the complex. This contribution decreases to zero by about 300-msec onset asynchrony. In vowel perception, however, analogous experiments have shown that a much shorter asynchrony (around 40 msec) is enough to ensure that a component does not influence a vowel's phonemic category. The three experiments reported here demonstrate that this difference in the utility of onset time as a grouping cue does not arise because of differences in stimulus structure, but rather is due to the perceptual task. They show that the onset asynchrony needed in a pitch-matching experiment to remove the contribution that a mistuned component makes to the pitch of a vowel is the same as that needed to remove the contribution to the pitch of a flat-spectrum complex tone. They further show that a much smaller onset asynchrony is needed to perceptually remove the same harmonic from a vowel for the calculation of vowel quality. The implication of this result for models of auditory grouping is discussed.

Adult↗