Judging time-to-passage of looming sounds: Evidence for the use of distance-based information.

Perceptual judgments are an essential mechanism for our everyday interaction with other moving agents or events. For instance, estimation of the time remaining before an object contacts or passes us is essential to act upon or to avoid that object. Previous studies have demonstrated that participants use different cues to estimate the time to contact or the time to passage of approaching visual stimuli. Despite the considerable number of studies on the judgment of approaching auditory stimuli, not much is known about the cues that guide listeners' performance in an auditory Time-to-Passage (TTP) task. The present study evaluates how accurately participants judge approaching white-noise stimuli in a TTP task that included variable occlusion periods (portion of the presentation time where the stimulus is not audible). Results showed that participants were able to accurately estimate TTP and their performance, in general, was weakly affected by occlusion periods. Moreover, we looked into the psychoacoustic variables provided by the stimuli and analysed how binaural cues related with the performance obtained in the psychophysical task. The binaural temporal difference seems to be the psychoacoustic cue guiding participants' performance for lower amounts of occlusion, while the binaural loudness difference seems to be the cue guiding performance for higher amounts of occlusion. These results allowed us to explain the perceptual strategies used by participants in a TTP task (maintaining accuracy by shifting the informative cue for TTP estimation), and to demonstrate that the psychoacoustic cue guiding listeners' performance changes according to the occlusion period.

Depth cues and perceived audiovisual synchrony of biological motion.

BACKGROUND: Due to their different propagation times, visual and auditory signals from external events arrive at the human sensory receptors with a disparate delay. This delay consistently varies with distance, but, despite such variability, most events are perceived as synchronic. There is, however, contradictory data and claims regarding the existence of compensatory mechanisms for distance in simultaneity judgments. PRINCIPAL FINDINGS: In this paper we have used familiar audiovisual events--a visual walker and footstep sounds--and manipulated the number of depth cues. In a simultaneity judgment task we presented a large range of stimulus onset asynchronies corresponding to distances of up to 35 meters. We found an effect of distance over the simultaneity estimates, with greater distances requiring larger stimulus onset asynchronies, and vision always leading. This effect was stronger when both visual and auditory cues were present but was interestingly not found when depth cues were impoverished. SIGNIFICANCE: These findings reveal that there should be an internal mechanism to compensate for audiovisual delays, which critically depends on the depth information available.

Avaliação da radiopacidade de alguns cimentos endodônticos por meio do sistema de imagem digital digora / Evaluation of some endodontic sealer radiopacity using digora digital image system

Este trabalho avaliou a radiopacidade de alguns cimentos endodônticos por meio do sistema de imagem digital Digora. As medidas digitais foram transformadas em milímetros de alumínio, comparadas entre si e com a radiopacidade de dentina humana. Os resultados mostraram que os cimentos testados em ordem crescente de radiopacidade foram: Sealapex, Endomethasone, Pro Canal, Sealer 26, Pulp Fill, Endofil da Dentsply, Pulp Canal Sealer, Endofil da Herpo, AH Plus e Top Seal. Todos estavam dentro das exigências nº 57 da ADA, com exceção do Sealapex, Endomethasone e Pro Canal.