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T Houtgast

Publications and source records attributed to T Houtgast.

10 recordsLinked to original sources
PubMed1992

A precedence effect in the perception of inter-aural cross correlation.

Does the precedence effect, well known in the field of sound localization or lateralization, also apply to other percepts based on binaural processing? We have compared, with one and the same experimental paradigm, a manifestation of the traditional precedence effect in lateralization with a possible similar effect in the perception of diffuseness or compactness of a sound image. With dichotic headphone stimulation, lateralization was controlled by the inter-aural time delay (IATD), and diffuseness/compactness by the inter-aural cross correlation (IACC). The experimental paradigm rests on the principle of estimating the over-all sensation of a 20-ms noise burst, which was subdivided in two parts, with the relevant dichotic information (IATD or IACC) in the leading part being opposite to that in the trailing part. When each part is 10 ms, it is found that the overall sensation is slightly dominated by the information in the leading part, both for lateralization and for compactness/diffuseness. This dominance of the leading part can be compensated by a certain decrease of its duration and/or amplitude relative to that of the trailing part. It is found that this quantitative measure for the 'strength' of the precedence effect for the present stimulus is essentially the same for IATD and IACC, suggesting that the precedence effect does not apply exclusively to sound localization or lateralization, but to at least one other percept based on binaural processing as well, namely the processing of inter-aural cross correlation.

Acoustic Stimulation↗
PubMed1992

Signal detection in temporally modulated and spectrally shaped maskers.

The first part of this paper presents several experiments on signal detection in temporally modulated noise, yielding a general approach toward the concept of comodulation masking release (CMR). Measurements were made on masked thresholds of both long- and short-duration, narrow-band signals presented in a 100% sinusoidally amplitude-modulated (SAM) noise masker (modulation frequency 32 Hz), as a function of masker bandwidth from 1/3 oct up to 13/3 octs, while the masker band was geometrically centered at signal frequency. With the short-duration signals placed in the valley of the masker, a substantial CMR (i.e., a decrease of masked threshold with increasing masker bandwidth) was found, whereas for the long-duration signals CMR was smaller. Furthermore, investigations were carried out to determine whether CMR changes when the bandwidth of the signals, consisting of bandpass impulse responses, is increased. The data indicate that substantial CMR remains even when all masker bands contain a signal component, thus minimizing across-channel differences. This finding is not in line with current models accounting for the CMR phenomenon. The second part of this paper concerns signal detection in spectrally shaped noise. Also investigated was whether release from masking occurs for the detection of a pure-tone signal at a valley or a peak of a simultaneously presented masking noise with a sinusoidally rippled power spectrum, when this masker was preceded and followed by a second noise (temporal flanking burst) with an identical spectral shape as the on-signal noise. Similar to CMR effects for temporal modulations, the data indicate that coshaping masking release (CSMR) occurs when the signal is placed in a valley of the spectral envelope of the masker, whereas no release from masking is found when the signal is placed at a peak of the spectral envelope of the masker. The implications of these experiments for measures of spectral and temporal resolution are discussed.

Acoustics↗
PubMed1990

Efficient across-frequency integration in short-signal detection.

A series of experiments was performed on the influence of bandwidth on the masked threshold of brief deterministic signals in continuous broadband noise. The signal bandwidth is quantified by the number (n) of constituent 1/3-oct bands. For n increasing from 1 to typically 9, the masked-threshold level in the constituent 1/3-oct bands is found to decrease by 8 log(n). This integration rule is obtained when each of the 1/3-oct bands covered by the signal equally contributes to detection, i.e., that, for each of these 1/3-oct bands, the difference between signal level and the individual masked-threshold level is the same. It was found that this integration rule also applies to noncontiguous signal spectra and that it remains intact over a broad range of masker levels. Commonly, the masked threshold of compound signals (for instance, n frequency components with a spacing of typically 1/3 oct), relative to the masked threshold of single-component signals, has been described by a 5 log(n) integration rule. However, this rule was obtained for signal durations of typically 100 ms or more. For the present brief signals (typically 10 ms or less), the across-frequency integration is found to be more effective.

Acoustic Stimulation↗
PubMed1990

Spectro-temporal integration in signal detection.

This paper is concerned with aspects of temporal integration and across-frequency integration in signal detection. Previous experiments on the detection of brief broadband signals (clicks) in continuous broadband noise revealed efficient spectral integration. The extent to which this effect is restricted to a critical time window was investigated by manipulating the temporal relations among the signal components in different frequency regions. In a typical experiment, the signal consists of nine brief Gaussian-shaped tone pulses, equally distributed at 1/3-oct intervals, each with a spectral width of about 1/3 oct, and each equally detectable in white noise. In the synchronized condition (i.e. coinciding peaks of the nine Gaussian envelopes), the detection threshold is reached when the levels of the nine individual tone pulses are about 8 dB below their individual threshold levels (efficient spectral integration). When the signal is progressively desynchronized (i.e. noncoinciding peaks of the Gaussian envelopes), detection threshold is found to increase. This suggests that efficient spectral integration in signal detection is confined to a narrow time window, with a typical value of 30 ms. Similar experiments were performed with respect to the efficiency of temporal integration. For constant-duration signals (100 ms), the detection threshold is found to increase when progressively widening signal bandwidth. The data indicate that the efficient temporal integration in signal detection is confined to a narrow frequency window, which, not surprisingly, corresponds to the critical bandwidth.

Adult↗
PubMed1986

Growth of pulsation threshold of a suppressed tone as a function of its level.

The pulsation threshold (PT) was measured at the frequency of a probe tone in a two-tone stimulus. A suppressor tone was higher in frequency than the probe tone and was fixed in level. As the level of the probe tone was increased, three regions of performance were observed: (1) for probe tone levels below simultaneous masked threshold (SMT), PT was the same as that measured for the suppressor alone, (2) for levels above SMT, PT increased linearly with level, indicating a constant amount of suppression in dB, and (3) for higher levels a recruitment-like phenomenon was observed, in which the PT increased faster than the probe level. The maximum amount of suppression observed was equal to the difference between the PT and SMT for the suppressor alone. One interpretation is that the suppressor reduces excitation on the slopes of its own excitation pattern by the same amount that it reduces the additional excitation from a probe tone. These results are consistent with physiological data, where the amount of suppression is determined by the suppressor and is independent of the level of the probe tone.

Acoustic Stimulation↗
PubMed1985

Spectral sharpness and vowel dissimilarity.

The effect of sharpening or smoothing the spectral envelopes of synthetic vowel-like sounds on the dissimilarities perceived among these sounds was investigated by means of triadic comparisons. When a spectral envelope (dB on a log-frequency scale) is considered the sum of a series of sinusoidal spectral modulations (or ripples) of different densities (the ripple spectrum), spectral sharpening or smoothing can be described as an amplification or attenuation of a part of the original ripple spectrum. For a set of nine sounds comprising different degrees of spectral sharpening of a single vowel, the perceived dissimilarities were found to be dominated by a specific part of the ripple spectrum, i.e., by spectral modulations with a density of about 2 ripples/oct. The possible role of lateral suppression in relation to this dominant region is discussed. For a set of 18 sounds comprising six vowels, each in three different versions (sharpened, normal, or smoothed), the dissimilarities were found to be determined mainly by the global shape of the spectral envelopes, i.e., by spectral modulations up to about 1.5-2 ripples/oct. Details of the spectral envelope (including the region of 2 ripples/oct where lateral suppression is effective) appear to be of minor influence on vowel dissimilarities.

Auditory Perception↗