Acoustic Specification of Object Properties
Jeffrey B. Wagman
Michael T. Turvey
A BOTTLE SITS unseen on the kitchen counter. Your elbow clips it inadvertently and sends it hurtling towards the floor. As you cringe, waiting for the crash, what you hear is not a shattering mess but a harmless bounce. The impact of glass on linoleum has set the materials into vibration, generating compression waves in the air. Somehow, from this sound structure, you know that the bottle did not break. Moreover, the people listening in the dining room heard something bounce as well. Let's focus on those listeners whose only contact with the event is from sound. What else do they know about what happened? Can they hear, for example, that the fallen object was made of glass, that it was a bottle, whether it was large or small, full or empty?
The preceding questions concern what listeners perceive about events happening around them. On the basis of its inattention to such questions, the science of perception can be considered skeptical that audition makes us aware of our surroundings with anything approaching the level of precision that vision allows (Jenkins, 1985). Hearing's specialties are thought to lie in perceiving speech and music. Beyond orienting the listener to the direction of a crash, hearing is not considered to be of much use in obtaining information about geometric properties, such as letting us know the sizes and shapes of objects. At least this has been the bias of orthodox approaches to perception. Shape perception and space perception are the traditional province of vision; pitch perception and loudness perception are the traditional domain of audition. Whereas vision is about awareness of environmental properties, audition seems to be largely about the awareness of sound as such.
Orthodoxy, of course, is likely to inspire heterodoxy. For perception, a contrary treatment can be found in the ecological approach of James J. Gibson. A major innovation is its focus on perceiving object properties rather than sound properties—hearing a small, hollow, glass object falling onto a hard surface rather than a loud, low-pitched, brief sound. In what follows, we describe this approach in general terms. From this description, it will become apparent that limiting the perception of geometric properties to the domain of vision is more tradition than necessity. Subsequent sections will address the lawfulness of acoustic structure that ought to permit auditory perception of geometric properties. Finally, we summarize research that documents listeners' success.
The ecological approach to perception is a metatheory. As such, it describes a particular conceptualization of how we can be aware of our surroundings. In general, meta- theories endorse a particular style of framing questions, promote certain strategies for