As good as the real thing? Performance differences for live versus recorded stimuli in an everyday listening task

In an attempt to understand the influence of stimulus presentation method for a typical everyday listening task, test subject performance in a dropped-rod length-estimate experiment was compared for three cases: 1) live presentation of stimuli, 2) playback of binaural stimuli as recorded from an acoustic head and torso simulator, and 3) diotic presentation of monaurally recorded stimuli. Live presentation of stimuli has already been used by C. Carello, et al. [Psychological Science 9, 211-214 (1998)] to demonstrate that humans can hear reasonably well the length of wooden dowels dropped onto hard surfaces. This experiment was performed to assess the significance of the presentation technique and to better understand the underlying acoustic structure important for length perception. Normal-hearing test subjects were seated facing away from an acoustically transparent but visually opaque screen. Test subjects listened to recordings presented via headphones and to the live presentation of wooden dowels of various lengths being dropped on a linoleum floor behind the screen. The subjects were asked to produce estimates of the rod lengths by positioning a moveable surface in such a way that it corresponded to a just-reachable distance between it and a stationary surface. In an attempt to make the task as natural as possible, the recording, playback, and live presentation of the stimuli all occurred in the same acoustically-normal room. Recordings were made in a position typical of where the test subject would be seated, thereby maintaining a similar impression of both the direct and reflected sound as allowed for by the binaural recording technique. The results from this experiment indicate that the use of binaurally-recorded test stimuli for similar everyday-sound listening experiments may produce results, in normal hearing listeners, that are very similar to those which can be obtained with live stimuli presentation. Monaurally-recorded stimuli should be used with caution.