(My wife Alexis and I in Marseille)

I. Human echolocation: like bats, dolphins and many other animals, humans are to make determinations about their environment using echoes. In our experiment (Rosenblum, Gordon & Jarquin, 2000) sighted, but blindfolded listeners were able to detect the distance of a surface 3 to 12 feet away using reflected sound. Subjects repeatedly produced a sound (e.g., saying "Hello" several times) directed toward a large reflective wall. After echolocating for a few moments subjects were able to walk to the position of the wall (after it had been removed). This ability was slightly improved by walking during the echolocation. Results from this experiment suggest the potential of echolocation to enhance visual guidance. The improved performance from movement further suggests the use of dynamic information to support our echolocation ability.

Download a PDF version of these papers:

Rosenblum, L.D, Gordon, M.S. & Jarquin, L. (2000). Echolocating distance by moving and stationary listeners. Ecological Psychology, 12(3), 181-206.

Schwitzgebel, E. & Gordon, M.S. (in press). How well do we know our own conscious experience? The case of human echolocation. Philosophical Topics.

II. Auditory occlusion perception (Gordon & Rosenblum, in preparation) was tested by asking blindfolded, sighted listeners to make judgements about sound projected through an aperture. Subjects listened to recorded crowd noise played from six speakers through either two horizontally sliding panels (akin to a sliding door open to various widths) or one vertically sliding panel (pictured to the right). After a few moments of listening to the sound subjects responded if they thought the aperture would have allowed them to walk umimpeded through its extent (without turning their bodies, or ducking their heads). Overwhelmingly subjects were accurate in their assessment of the aperture. Listener sensitivity to the size of the aperture suggests that occluded sound can be a compelling source of information about the environment. Listeners were able use silence (from blocking the sound in certain locations) to guide behavior toward the aperture. These results may also suggest the use of ego-centric perceptual information - wherein perceivers detect information in a way relative to their own bodies.

(picture of the vertical aperture experiment)

III. Auditory looming perception (Rosenblum, Gordon & Wuestefeld, in press): This research examines accuracy in an auditory time-to-arrival task when performance feedback is first provided to listeners and is subsequently withdrawn. Listeners made judgments about the time to arrival of an approaching car based on various portions of the event. Listeners participated in three experimental sessions on consecutive days. The experimental group received no feedback during the first session, feedback during the second session, and no feedback during the final session. When feedback was withdrawn, the higher performance level attained during training was retained. This result is in contrast to previous research presumabley due to our use of more 'ecologically valid' stimuli and feedback methods. By placing our subjects in a paradigm that closely parallelled real-life judgements, and providing them with precise graphical feedback retention of time-to-arrival accuracy was facilitated.

Download the PDF of this paper:

Rosenblum, L. D., Gordon, M. S. & Wuestefeld, A. P. (2000). Effects of performance feedback and feedback withdrawal on auditory looming perception. Ecological Psychology, 12(4), 273 - 292.

IV. The Ambulance Problem - an audio-visual approach to age-related changes (Gordon & Rosenblum, in preparation). To successfully detect an ambulance, approaching from outside our visual field, we must auditorily determine its location and trajectory while perceiving our own self-motion. While research has found that listeners can detect acoustic time-to-arrival information, it is unclear how introducing an optic flow field will influence these judgements. To test this question, listeners were asked to judge the time-to-arrival of a sound source approaching from behind - with or without presentation of visual and acoustic flow fields. Several combinations of the looming target and observer's velocity were presented. The effects of optic flow varied with the speed difference between the observer and ambulance. No influence of acoustic flow was found.

Pictured to the right is one of the stimuli from this project. The movie features video footage of the road in front of the vehicle with simultaneous binaural recordings of the ambulance passing. The binaural recording is made by placing microphones in the 2 ears of a listener; this technique makes for very high quality recordings that preserve the spatial quality of the environment. You will need to listen to the movie through headphones for the full effect.

(Movie of ambulance passing car with binaural recording)

V. Acoustic Calibration - Previous visual research has shown that observers determine their speed, and direction of motion from the flow of the visual environment around them (see Warren, 1998). This visual flow information has been found to cause observers to recalibrate their movements in conjuction with their perceived speed and path (Pick, Rieser, Wagner & Garing, 1999; Rieser, Pick, Ashmead & Garing, 1995). We are curious if auditory information is also sufficient to cause perceivers to recalibrate their movement.

To establish the salience of auditory information for perceptually-based calibration we are employing the following methods. Binaural recordings were taken of an actor moving through a noisy hallway at several speeds. As previously discussed binaural recordings are taken from two very small microphones placed within the ears of an observer. The resultant auditory stimuli capture very accurately the acoustic experience of a listener - including the spatial qualities of an environment, and all of the sound sources therein. These recordings are played back to a listener walking on a treadmill. If the recordings simulate a faster walking speed than the pace of the listener on the treadmill it may cause him to assume that each step carries him faster and farther than actually occurs. This is tested by asking subjects to walk to a target after stepping off the treadmill. Results of this experiment are forthcoming.