Inhibiting the inhibition

The precedence effect describes the phenomenon whereby echoes are spatially fused to the location of an initial sound by selectively suppressing the directional information of lagging sounds (echo suppression). Echo suppression is a prerequisite for faithful sound localization in natural environments but can break down depending on the behavioral context. To date, the neural mechanisms that suppress echo directional information without suppressing the perception of echoes themselves are not understood. We performed in vivo recordings in Mongolian gerbils of neurons of the dorsal nucleus of the lateral lemniscus (DNLL), a GABAergic brainstem nucleus that targets the auditory midbrain, and show that these DNLL neurons exhibit inhibition that persists tens of milliseconds beyond the stimulus offset, so-called persistent inhibition (PI). Using in vitro recordings, we demonstrate that PI stems from GABAergic projections from the opposite DNLL. Furthermore, these recordings show that PI is attributable to intrinsic features of this GABAergic innervation. Implementation of these physiological findings into a neuronal model of the auditory brainstem demonstrates that, on a circuit level, PI creates an enhancement of responsiveness to lagging sounds in auditory midbrain cells. Moreover, the model revealed that such response enhancement is a sufficient cue for an ideal observer to identify echoes and to exhibit echo suppression, which agrees closely with the percepts of human subjects

Auditory masking and the Precedence Effect in Studies of Musical Timekeeping

Musical timekeeping is an important and evolving area of research with applications in a variety of music education and performance situations. Studies in this field are of ten concerned with being able to measure the accuracy or consistency of human participants, for whatever purpose is being investigated. Our initial explorations suggest that little has been done to consider the role that auditory masking, specifically the precedence effect, plays in the study of human timekeeping tasks. In this paper, we highlight the importance of integrating masking into studies of timekeeping and suggest areas for discussion and future research, to address shortfalls in the literature

Transient Analysis for Music and Moving Images: Consideration for Television Advertising

In audiovisual composition, coupling montage moving images with music is common practice. Interpretation of the effect on an audioviewer's consequent interpretation of the composition is discursive and unquantified. Meth-odology for evaluating the audiovisual multimodal inter-activity is proposed, developing an analysis procedure via the study of modality interdependent transient structures, explained as forming the foundation of perception via the concept of Basic Exposure response to the stimulus. The research has implications for analysis of all audiovisual media, with practical implications in television advertis-ing as a discrete typology of target driven audiovisual presentation. Examples from contemporary advertising are used to explore typical transient interaction patterns and the consequences of which are discussed from the practical viewpoint of the audiovisual composer

Subjective evaluation of an emerging theory of low-frequency sound source localization in closed acoustic spaces

An earlier reported theory of low-frequency sound-source localization within closed acoustic spaces proposed that virtual image acuity is strongly dependent on sufficient inter-arrival time between a direct sound and its first reflection. This current study aims to test the theory’s predictions by subjective experiment where participants are required to indicate perceived sound source direction, but without knowledge of loudspeaker location. Test signals of frequencies 40 Hz to 115 Hz take the form of either windowed sine or square waves. Results confirm broad agreement with theoretical expectations and support the conjecture, contrary to common expectation, that low-frequency sound localization within the context of closed acoustic spaces is possible, although strongly dependent on system configuration and size of a listening space

Auditory, Visual And Somatosensory Localization Of Piano Tones: A Preliminary Study

The paper presents an experiment in which subjects had to localize headphone-reproduced binaural piano tones while in front of a grand Disklavier instrument. Three experimental conditions were designed: when the fallboard was closed the localization was auditory only; when the fallboard was open the localization was auditory and visual, since the Disklavier’s actuated key could be seen moving down while the corresponding note was produced; when the listener actively played the note the localization was auditory, visual and somatosensory. In all conditions the tones were reproduced using binaural recordings previously acquired on the same instrument. Such tones were presented either transparently or by reversing the channels. Thirteen subjects participated in the experiment. Results suggest that if auditory localization associates the tone to the corresponding key, then the visual and somatosensory feedback refine the localization. Conversely, if auditory localization is confused then the visual and somatosensory channels cannot improve it. Further experimentation is needed to explain these results in relation with i) possible activation of the auditory precedence effect at least for some notes, and ii) potential locking of the sound source position that visual and/or somatosensory cues might cause when subjects observe a key moving down, or depress it

Developmental changes in sound localization precision under conditions of the precedence effect.

The ability to give perceptual priority to an original sound source and ignore later-arriving echoes of that sound is termed the law of the first wave-front , or the precedence effect (PE). Little attention has been paid to the influence that echoes exert on localization accuracy for the leading sound. The present study investigated localization precision of children and adults in the presence of a simulated echo, using the minimal audible angle (MAA) task, which indicates the smallest change in the location of a sound that can be reliably discriminated. Three age groups were tested: 18-months, 5-years, and adults. Each age group was tested with one single-source (SS) stimulus, and two precedence effect (PE) stimuli: LEAD, in which the original sound shifted from midline and the echo remained at midline, and LAG, where the reverse occurred. Subjects were tested using an adaptive, 2-down/1-up, psychophysical algorithm. For all age groups, MAA thresholds were smallest for SS, larger for LEAD and largest for LAG. For all three stimulus conditions, the 18-month-olds\u27 thresholds were significantly larger than those of either 5-year-olds or adults. Five-year-olds\u27 MAA thresholds for SS sounds were very near to those of adults. However, their thresholds for the PE stimuli were significantly higher than those of adults\u27, and closer to those of 18-month-olds. When a lagging sound is inaudible as a separate auditory event, the auditory system presumably treats the leading and lagging sound as components of the same auditory percept, and uses both signals to compute the position of the sound source. The leading sound, which signals the onset of an auditory event, is assigned perceptual dominance thereby diminishing the nervous system\u27s interaural sensitivity for the later-arriving echo. This and related work has raised important questions concerning the neural mechanisms involved in spatial hearing in adults and children, especially those aspects which involve an active suppression of superfluous signals