Auditory Localization in Rooms: Acoustic Analysis and Behavior

In an ordinary room, reverberation and echoes in the signals reaching a listener’s ears influence auditory localization performance. The energy of the echoes and reverberation depends on the position of the listener in the room as well as on the position of the sound source relative to the listener. In this paper, the effects of echoes and reverberation are quantified through analysis of reverberant HeadRelated Transfer Functions (HRTFs) measured in an ordinary classroom. HRTFs were measured for several human listeners and a KEMAR acoustic manikin at four different listener positions in the room and multiple source positions relative to the listener. Azimuthal localization performance was also measured for several listeners in the room as a function of listener position. Compared to the acoustic cues it was found to be less sensitive to a change in room location. The only similarity was found between the magnitude of frequency-to-frequency variations in basic localization cues and the variability in localization performance, demonstrating that localization accuracy decreases with increasing reverberant energy. Introduction In a room, the ability of human listeners to localize sounds is influenced by echoes and reverberation (which are henceforth collectively referred to as “reverberation,” for brevity; Santarelli, 2000). The effect of reverberation can be both beneficial and detrimental, improving distance perception and degrading azimuthal localization. However, the pattern of reverberation differs from room to room as well as from position to position within a given room. For a listener in the center of a room, most reflective surfaces are relatively far from the listener and reflections are diffuse for all source positions. On the other hand, when the listener is close to a wall, prominent early reflections arise whose magnitude and timing depend on the location of the source relative to the walls and to the listener. The goal of this study is to analyze how localization cues in the signals reaching a listener’s ears are influenced by reverberation and to evaluate whether acoustic effects can account for how localization performance varies with a listener’s position in a room. A set of head-related transfer functions (HRTFs; see Santarelli, 2000) was measured for a manikin (KEMAR) located at different positions in a classroom. The effect of reverberation on interaural differences and spectral magnitude is evaluated by computing how these cues vary with source position relative to the listener and listener location relative to the room. Results are compared to behavioral localization results (Kop