Massimo Grassi

Do we hear size or sound? Balls dropped on plates

The aim of this study is to examine whether it is possible to recover directly the size of an object from the sound of an impact. Specifically, the study is designed to investigate whether listeners can tell the size of a ball from the sound when it is dropped on plates of different diameters (on one, two, or three plates in Experiments 1, 2, and 3, respectively). In this paradigm, most of the sound produced is from the plate rather than the ball. Listeners were told neither how many different balls or plates were used nor the materials of the balls and plates. Although listeners provided reasonable ball size estimates, their judgments were influenced by the size of the plate: Balls were judged to be larger when dropped on larger plates. Moreover, listeners were generally unable to recognize either ball and plate materials or the number of plates used in Experiments 2 and 3. Finally, various acoustic properties of the sounds are shown to be correlated with listeners’ judgments.

MLP: A MATLAB toolbox for rapid and reliable auditory threshold estimation

In this article, we present MLP, a MATLAB toolbox enabling auditory thresholds estimation via the adaptive maximum likelihood procedure proposed by David Green (1990, 1993). This adaptive procedure is particularly appealing for those psychologists who need to estimate thresholds with a good degree of accuracy and in a short time. Together with a description of the toolbox, the present text provides an introduction to the threshold estimation theory and a theoretical explanation of the maximum likelihood adaptive procedure. MLP comes with a graphical interface, and it is provided with several built-in, classic psychoacoustics experiments ready to use at a mouse click.

The subjective duration of ramped and damped sounds.

Two experiments demonstrate that the perceived durations of sounds as long as 1 sec are influenced by the sounds’ amplitude envelopes, extending Schlauch, Ries, and DiGiovanni’s (2001) observations on sounds of 200-msec duration. Sounds with a monotonic decay (i.e., damped sounds) are heard as substantially shorter than both steady sounds and those with a monotonic increase of level (i.e., ramped sounds). Neither a reaction time (Experiments 1 and 2) nor a staircase (Experiment 2) procedure supported a sensory explanation for these different subjective durations. The results are compatible with the suggestion of Stecker and Hafter (2000) that listeners exclude part of the tails of damped sounds in the computation of their subjective durations.

Audiovisual bounce-inducing effect: attention alone does not explain why the discs are bouncing.

Two discs moving from opposite points in space, overlapping and stopping at the other discs starting point, can be seen as either bouncing or streaming through each other. With silent displays, observers report the discs as streaming, whereas if a sound is played when the discs touch each other, observers report the discs as bouncing. The origin of the switch from streaming to bouncing response is not known yet. The sound either shifts perception toward that of an impact-elastic event (i.e., a bounce) or subtracts the attention that is necessary to perceive the discs as streaming. We used either impact-similar (abrupt amplitude attack, gradual decay) or impact-dissimilar sounds (gradual amplitude attack, abrupt decay) and found that the first sounds induce the bouncing response, whereas the latter, although as distracting as the first, render streaming and bouncing responses equally frequent at most. We interpret the audiovisual bouncing effect as resulting from attention subtraction, which raises the number of bounce responses in comparison with silent displays, and from perception, which further increments the number of bounce responses and turns the response into a strong bounce response.

When Ears Drive Hands: The Influence of Contact Sound on Reaching to Grasp

Background Most research on the roles of auditory information and its interaction with vision has focused on perceptual performance. Little is known on the effects of sound cues on visually-guided hand movements. Methodology/Principal Findings We recorded the sound produced by the fingers upon contact as participants grasped stimulus objects which were covered with different materials. Then, in a further session the pre-recorded contact sounds were delivered to participants via headphones before or following the initiation of reach-to-grasp movements towards the stimulus objects. Reach-to-grasp movement kinematics were measured under the following conditions: (i) congruent, in which the presented contact sound and the contact sound elicited by the to-be-grasped stimulus corresponded; (ii) incongruent, in which the presented contact sound was different to that generated by the stimulus upon contact; (iii) control, in which a synthetic sound, not associated with a real event, was presented. Facilitation effects were found for congruent trials; interference effects were found for incongruent trials. In a second experiment, the upper and the lower parts of the stimulus were covered with different materials. The presented sound was always congruent with the material covering either the upper or the lower half of the stimulus. Participants consistently placed their fingers on the half of the stimulus that corresponded to the presented contact sound. Conclusions/Significance Altogether these findings offer a substantial contribution to the current debate about the type of object representations elicited by auditory stimuli and on the multisensory nature of the sensorimotor transformations underlying action.

Audiovisual bounce-inducing effect: When sound congruence affects grouping in vision

Two disks moving from opposite points in space, overlapping, and stopping at one another’s starting point can be seen as either bouncing off one another or streaming through one another. With silent displays, observers report streaming, whereas, if a sound is played when the disks are in the overlap region, observers report bouncing. The change in perception is thought to be modulated by a lack of attention that inhibits the integration of the motion signal when disks overlap and by the sound that increases the congruence of the display, in comparison with a real elastic bounce. Here, we accompanied the disks’ motion with either a bounce-congruent sound (a billiard ball) or with bounce-incongruent sounds (a water drop, a firework). When the sound was switched on 200 msec before the disks’ overlap, (1) all the audiovisual displays induced more bounce responses than did the silent display, but (2) the bounce-congruent sound induced more bounce responses than did the bounceincongruent sounds. However, when the sound was switched on at the disks’ overlap, only the first result was observed. These results highlight both the role of attention and that of sound congruence.

PSYCHOACOUSTICS: a comprehensive MATLAB toolbox for auditory testing

PSYCHOACOUSTICS is a new MATLAB toolbox which implements three classic adaptive procedures for auditory threshold estimation. The first includes those of the Staircase family (method of limits, simple up-down and transformed up-down); the second is the Parameter Estimation by Sequential Testing (PEST); and the third is the Maximum Likelihood Procedure (MLP). The toolbox comes with more than twenty built-in experiments each provided with the recommended (default) parameters. However, if desired, these parameters can be modified through an intuitive and user friendly graphical interface and stored for future use (no programming skills are required). Finally, PSYCHOACOUSTICS is very flexible as it comes with several signal generators and can be easily extended for any experiment.

Sex Difference in Subjective Duration of Looming and Receding Sounds

Looming sounds (sounds increasing in intensity over time) are more salient than receding sounds (a looming sound reversed in time). For example, they are estimated as being longer, louder, and more changing in loudness than receding sounds. Some authors interpret the looming salience as evolutionarily adaptive, because it increases the margins of safety of the perceiver in the case of preparatory behaviours (eg a motor reaction to an approaching sound source). Recently, Neuhoff et al (2009, Journal of Experimental Psychology: Human Perception and Performance 35 225–234) found that females more than males show overestimation of the spatiotemporal properties of virtually simulated looming sound sources. Here, I investigated whether the sex difference could be observed for the subjective duration of looming and receding sounds, and found that females more than males overestimate the duration of looming sounds in comparison to receding sounds.

The subjective duration of audiovisual looming and receding stimuli

Looming visual stimuli (log-increasing in proximal size over time) and auditory stimuli (of increasing sound intensity over time) have been shown to be perceived as longer than receding visual and auditory stimuli (i.e., looming stimuli reversed in time). Here, we investigated whether such asymmetry in subjective duration also occurs for audiovisual looming and receding stimuli, as well as for stationary stimuli (i.e., stimuli that do not change in size and/or intensity over time). Our results showed a great temporal asymmetry in audition but a null asymmetry in vision. In contrast, the asymmetry in audiovision was moderate, suggesting that multisensory percepts arise from the integration of unimodal percepts in a maximum-likelihood fashion.

Audio-Visual, Visuo-Tactile and Audio-Tactile Correspondences in Preschoolers

Interest in crossmodal correspondences has recently seen a renaissance thanks to numerous studies in human adults. Yet, still very little is known about crossmodal correspondences in children, particularly in sensory pairings other than audition and vision. In the current study, we investigated whether 4-5-year-old children match auditory pitch to the spatial motion of visual objects (audio-visual condition). In addition, we investigated whether this correspondence extends to touch, i.e., whether children also match auditory pitch to the spatial motion of touch (audio-tactile condition) and the spatial motion of visual objects to touch (visuo-tactile condition). In two experiments, two different groups of children were asked to indicate which of two stimuli fitted best with a centrally located third stimulus (Experiment 1), or to report whether two presented stimuli fitted together well (Experiment 2). We found sensitivity to the congruency of all of the sensory pairings only in Experiment 2, suggesting that only under specific circumstances can these correspondences be observed. Our results suggest that pitch-height correspondences for audio-visual and audio-tactile combinations may still be weak in preschool children, and speculate that this could be due to immature linguistic and auditory cues that are still developing at age five.