Publicação
Perceiving audiovisual synchrony as a function of stimulus distance
| Resumo: | Audiovisual perception is still an intriguing phenomenon, especially when we think about the physical and neuronal differences underlying the perception of sound and light. Physically, there is a delay of ~3ms/m between the emission of a sound and its arrival to the observer, whereas speed of light makes its delay negligible. On the other hand, we know that acoustic transduction is a very fast process (~1ms) while photo-transduction is quite slow (~50 ms). Nevertheless, audio and visual stimuli that are temporally mismatched can be perceived as a coherent audiovisual stimulus, although a sound delay is often required to achieve a better perception. A Point of Subjective Simultaneity (PSS) that requires a sound delay might point both to a perceptual mechanism that compensates for physical differences or to one that compensates for the transduction differences, in the perception of audiovisual synchrony. In this study we analyze the PSS as a function of stimulus distance to understand if individuals take into account sound velocity or if they compensate for differences in transduction time when judging synchrony. Using Point Light Walkers (PLW) as visual stimuli and sound of steps as audio stimuli, we developed presentations in a virtual reality environment with several temporal alignments between sound and image (-285ms to +300ms of audio asynchrony in steps of 30 ms) at different distances from the observer (10, 15, 20, 25, 30, 25 meters) in conditions which differ in the number of depth cues. The results show a relation between PSS and stimulation distance that is congruent with differences in velocity of propagation between sound and light (Experiment 1). Therefore, it appears that perception of synchrony across several distances is made possible by the existence of a compensatory mechanism for the slower velocity of sound, relative to light. Moreover, the number and quality of depth cues appears to be of great importance in the triggering of such a compensatory mechanism (Experiment 2). |
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| Autores principais: | Silva, Carlos César Loureiro |
| Ano: | 2011 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Audiovisual perception is still an intriguing phenomenon, especially when we think about the physical and neuronal differences underlying the perception of sound and light. Physically, there is a delay of ~3ms/m between the emission of a sound and its arrival to the observer, whereas speed of light makes its delay negligible. On the other hand, we know that acoustic transduction is a very fast process (~1ms) while photo-transduction is quite slow (~50 ms). Nevertheless, audio and visual stimuli that are temporally mismatched can be perceived as a coherent audiovisual stimulus, although a sound delay is often required to achieve a better perception. A Point of Subjective Simultaneity (PSS) that requires a sound delay might point both to a perceptual mechanism that compensates for physical differences or to one that compensates for the transduction differences, in the perception of audiovisual synchrony. In this study we analyze the PSS as a function of stimulus distance to understand if individuals take into account sound velocity or if they compensate for differences in transduction time when judging synchrony. Using Point Light Walkers (PLW) as visual stimuli and sound of steps as audio stimuli, we developed presentations in a virtual reality environment with several temporal alignments between sound and image (-285ms to +300ms of audio asynchrony in steps of 30 ms) at different distances from the observer (10, 15, 20, 25, 30, 25 meters) in conditions which differ in the number of depth cues. The results show a relation between PSS and stimulation distance that is congruent with differences in velocity of propagation between sound and light (Experiment 1). Therefore, it appears that perception of synchrony across several distances is made possible by the existence of a compensatory mechanism for the slower velocity of sound, relative to light. Moreover, the number and quality of depth cues appears to be of great importance in the triggering of such a compensatory mechanism (Experiment 2). |
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