Search PubMed⌕ Search

Biomedical subjects

G Canévet

Publications and source records attributed to G Canévet.

9 recordsLinked to original sources
PubMed2000

The perception of waning signals: decruitment in loudness and perceived size.

When a tone or broad-band noise sweeps smoothly from a moderate intensity to a low one, the loudness at the end of the sweep is far less than what would be predicted from its intensity. The accelerated reduction in loudness, which was first reported by Canévet (1986) and confirmed in several later reports, has been called loudness decruitment, and has been tentatively interpreted as the result of some form of adaptation. Since both simple and induced adaptation have distinctive temporal profiles, we undertook a series of studies in which we varied the duration of a tone whose intensity was continuously changing, to see whether the effect of duration on decruitment resembled the effects of duration on adaptation. We discovered that the magnitude of decruitment remained unaffected when the duration of the sweep was reduced far below the durations of 90 to 180 sec that have been used in previous studies. The same effect was observed for durations of around 20 sec, but it declined rapidly to a low level at the lowest duration of 1.0 sec. This temporal pattern is strikingly different from what has been reported for either simple or ipsilaterally induced adaptation, which suggests that neither form of adaptation can account for the entire effect. We also wanted to know whether an analogous phenomenon could exist for a sensory modality other than hearing. In the present study, observers were asked to judge the apparent size of a solid disk on a computer monitor, the disk increased or decreased continuously in area, or appeared as a series of separate areas, either in random order or in ordered progressions. We found that, as in the case of loudness, apparent size decreased more rapidly when the areas decreased continuously than would have been predicted from the actual areas themselves. We also found that some part of the accelerated shrinkage was due to a response bias in the observers' judgments that stemmed from knowledge that every value in a continuously changing series is predictably smaller (or larger, for a growing series). Whether the remaining part of the effect is a sensory phenomenon is an important issue for future research.

Adolescent↗
PubMed1990

The loudness of sounds that increase and decrease continuously in level.

A sound at a low level is heard as much softer after having decreased continuously from higher levels than if presented after a period of silence at that same low level. Canévet [Acustica 61, 256-264 (1986)] demonstrated this phenomenon for a tone that (1) decreased from 65 to 20 dB in 180 s; he also presented a tone that (2) increased from 20 dB, or (3) was presented as pairs of bursts at various levels in random order. Below about 40 dB, loudness changed most rapidly in the decreasing condition so that, at 20 dB, the tone was judged ten times softer than in conditions (2) and (3). In the present experiments, magnitude estimation was used to examine the possible role of judgmental biases and adaptation in this rapid loudness decline, which we call decruitment. Results show that decruitment did not come about because subjects made many successive loudness judgments; loudness declined as much when a tone was judged only twice, at the beginning and end of its 180-s decrease. In contrast, interrupting the decreasing tone so that it was heard only at 70 dB and 160 s later at 30 dB greatly diminished the decruitment. Similarly, pairs of 500-ms tone bursts presented at successively lower levels instead of continously decreasing did not show decruitment, suggesting that sequential biases are irrelevant. The likely cause of decruitment is sensory adaptation.

Attention↗
PubMed1989

The precedence effect: no evidence for an "active" release process found.

Hafter et al. [Auditory Function: The Neurobiological Bases for Hearing (Wiley, New York, 1988)] have reported that "post-onset adaptation," as measured with trains of high-frequency clicks in a lateralization paradigm, can instantly be released by presentation of an additional, short trigger signal, which is spectrally different from the click trains. As post-onset saturation may be one of the psychoacoustic components of the precedence effect, it has been investigated whether suitable trigger signals might also induce a release from echo inhibition. However, no evidence for such an "active" release process could be observed in a number of exploratory precedence-effect settings.

Acoustic Stimulation↗
PubMed1986

[Auditory localization and speech perception in noise. Preliminary study concerning 5 cases of perceptual deafness].

The experiments reported here examine the psychoacoustical bases for poor speech perception in noise by persons with sensorineural impairment. Two major hypotheses are tested. First, because persons with cochlear impairment are less able than normal-hearing persons to separate out incoming signals on the basis of spectral differences (a deficit referred to as reduced frequency selectivity), they are less able to localize one sound in the presence of other sounds. Second, this reduced localization ability makes it difficult for the hearing-impaired person to take advantage of the spatial separation of a target speech source and other interfering sources. Such separation is common in real environments and facilitates speech perception by normal-hearing persons. Tests of these hypotheses are conducted by means of detailed psychoacoustical measures of frequency selectivity, of localization and speech perception under masking.

Adolescent↗
PubMed1985

Simple and induced loudness adaptation.

Simple loudness adaptation is the decrease in loudness that takes place when a continuous sound is presented alone for a period of time. Simple adaptation normally occurs only when a sound is soft to begin with, no more than 30 dB above threshold; except for some persons with a retrocochlear lesion, sounds above 30 dB SL do not diminish in loudness over time. However, adaptation can be induced in at least two ways: (1) A steady sound to one ear, presented together with an intermittent sound to the contralateral ear, decreases in loudness by 50-60% within 3 min. (2) An otherwise steady sound that is intermittently increased in level by at least 5 dB becomes softer during its weaker periods. When, for example, a 40-dB tone is increased every 20 s to 60 dB for 15 s, its loudness decreases by about 50% within 3 min. We report measurements of both simple and induced adaptation on 10 persons listening to a 1 000-Hz tone via earphones or from a loudspeaker. The results provide an overview of both types of adaptation. They also permitted a correlational analysis that reveals some of the similarities and differences between the two kinds of adaptation.

Adaptation, Physiological↗
PubMed1983

Loudness adaptation, when induced, is real.

In two recent articles, Hood and Wade (1982) and Weiler et al. (1981) have argued that the loudness of a steady tone does not appear to decline over time unless listeners are given a reference sound by which to judge loudness. The present experiments show, by the method of successive magnitude estimation, that listeners do not need a reference sound in order (1) to track accurately the decline in the loudness of a tone slowly decreasing from 60 to 40 dB SPL or (2) to track the loudness decline of a constant-intensity tone under special conditions that lead to adaptation. Since a reference sound is not needed by listeners to track a decline in loudness, and since Hood and Wade and Weiler et al. have found a decline with a reference but not without, it follows that adding a reference sound to a sustained sound must induce adaptation that otherwise does not occur. In support of that interpretation, the present measurements show that when subjects are told to ignore the same reference sound as used by Hood and Wade and by Weiler et al.--an increment every 30 s to a steady tone--loudness still declines. The bigger the increment (20 dB v. 5 dB) and the longer (5 s v. 1 s), the more loudness declines. Thus, loudness adaptation may be induced not only by a contralateral intermittent sound (Botte et al., 1982) but also by an ipsilateral intermittent sound. However, under normal listening conditions at levels above about 30 dB SL, loudness does not adapt.

Acoustic Stimulation↗
PubMed1982

Loudness adaptation induced by an intermittent tone.

The loudness of a continuous 1000-Hz tone at 60 dB SPL was measured in the presence of an intermittent tone in the contralateral ear. Over 70 observers participated in a series of eight experiments. The method of successive magnitude estimation showed that the intermittent tone causes the steady tone to diminish in loudness within 2 or 3 min by 40% to 60%. The amount of this induced loudness adaptation depends weakly upon the presentation rate, frequency, and level of the contralateral tone. Loudness reduction of the steady tone is coupled with loudness enhancement of the intermittent tone in the opposite ear. Induced loudness adaptation was also revealed by interaural and cross-modality matching. Induced loudness adaptation depends strongly on interaural interaction and is probably related to lateralization and interaural funneling of loudness. Adaptation induced by an intermittent tone stands in marked contrast to the near absence of loudness adaptation, except near threshold, when a continuous sound is presented alone.

Acoustic Stimulation↗