A major problem for an auditory system exposed to sound in a reverberant environment is to distinguish reflections from true sound sources. Previous research indicates that the process of recognizing reflections is malleable from moment to moment. Three experiments report how ongoing input can prevent or disrupt the fusion of the delayed sound with the direct sound, a necessary component of the precedence effect. The buildup of fusion can be disrupted by presenting stimuli in alternation that simulate different reflecting surfaces. If buildup of fusion is accomplished first and then followed by an aberrant configuration, breakdown of the precedence effect occurs but it depends on the duration of the new sound configuration. The Djelani and Blauert (2001) finding that a brief disruption has no effect on fusion was confirmed; however, it was found that a more lengthy disruption produces breakdown.
"Similarly, listening to a series of sounds with identical locations and onset asynchronies produces a buildup of the precedence effect such that listeners report that echoes fade out across the presentation of several pairs regardless of presentation rate (Clifton & Freyman, 1989; Freyman, Clifton, & Litovsky, 1991). The results of these experiments along with other studies exploring the precise conditions that result in both the breakdown and buildup of the precedence effect are consistent with the hypothesis that listeners build complex models of the acoustically reflective surfaces in a room based on experience with sounds in that setting (Blauert, 1997; Clifton, Freyman, Litovsky, & McCall, 1994; Clifton, Freyman, & Meo, 2002; Freyman & Keen, 2006). Additionally, asymmetries arise in the buildup of the precedence effect that are not evident when onset asynchrony varies randomly from trial to trial (Clifton & Freyman, 1989; Grantham, 1996). "
[Show abstract][Hide abstract] ABSTRACT: The ability to isolate a single sound source among concurrent sources and reverberant energy is necessary for understanding the auditory world. The precedence effect describes a related experimental finding, that when presented with identical sounds from two locations with a short onset asynchrony (on the order of milliseconds), listeners report a single source with a location dominated by the lead sound. Single-cell recordings in multiple animal models have indicated that there are low-level mechanisms that may contribute to the precedence effect, yet psychophysical studies in humans have provided evidence that top-down cognitive processes have a great deal of influence on the perception of simulated echoes. In the present study, event-related potentials evoked by click pairs at and around listeners' echo thresholds indicate that perception of the lead and lag sound as individual sources elicits a negativity between 100 and 250 msec, previously termed the object-related negativity (ORN). Even for physically identical stimuli, the ORN is evident when listeners report hearing, as compared with not hearing, a second sound source. These results define a neural mechanism related to the conscious perception of multiple auditory objects.
[Show abstract][Hide abstract] ABSTRACT: Reflected sounds are often treated as an acoustic problem because they produce false localization cues and decrease speech intelligibility. However, their properties are shaped by the acoustic properties of the environment and therefore are a potential source of information about that environment. The objective of this study was to determine whether information carried by reflected sounds can be used by listeners to enhance their awareness of their auditory environment. Twelve listeners participated in two auditory training tasks in which they learned to identify three environments based on a limited subset of sounds and then were tested to determine whether they could transfer that learning to new, unfamiliar sounds. Results showed that significant learning occurred despite the task difficulty. An analysis of stimulus attributes suggests that it is easiest to learn to identify reflected sound when it occurs in sounds with longer decay times and broadly distributed dominant spectral components.
Military Psychology 01/2009; 22(1):24-40. DOI:10.1080/08995600903206461 · 0.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: La capacidad para percibir si el sonido que se escucha proviene desde la izquierda o derecha, arriba o abajo, detrás o adelante y qué tan cerca o lejos se encuentra la fuente sonora es de importancia capital tanto para animales como para seres humanos. La investigación sistemática sobre los aspectos evolutivos involucrados en el desarrollo de esta habilidad comenzó recién en la década del 80. El propósito de este trabajo es realizar una revisión de las principales investigaciones sobre el desarrollo de la habilidad para localizar sonidos directos y reflejados en neonatos y niños pequeños. Se discuten las principales hipótesis explicativas de los cambios evolutivos observados en esta habilidad y los tópicos que aún desafían a los expertos.
Revista latinoamericana de psicología 01/2009; · 0.64 Impact Factor
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