Using Sound to Create and Detect Occlusion of an Unseen Sound Source

ABSTRACT

In contrast to experimental settings, the environment within which we perceive and act contains clutter (objects other than the target of perception and/or action). While numerous empirical investigations have revealed that clutter can significantly affect auditory spatial judgments, the present study is believed to be the first study to investigate the ability of individuals to recognize and produce occlusion when relying solely on sound. Participants in Experiment 1 were presented with the task of reporting whether a sound-producing object was occluded whereas participants in Experiment 2 were required to create the same levels of occlusion participants in Experiment 1 were exposed to. With regard to the detection of occlusion, individuals tended to report the sound source as unoccluded when it was obstructed less than 50% and as occluded when obstructed greater than 50%. When creating occlusion, participants were most accurate at the extremes but less proficient at intermediate levels. Interestingly, the findings further revealed that participant’s initial experience significantly affected their ability to detect, but not create, occlusion. The results of the present study provide strong initial evidence as to the sensitivity of individuals to detect occlusion.

KEYWORDS:

• Perception
• action
• occlusion
• perceptual accuracy
• space

Disclosure Statement

No potential conflict of interest was reported by the authors.

Notes

1. In terms of acoustics, a distinction has been made between obstruction and occlusion. In both instances, an intermediary object is placed between a sound source and observer and in both instances that object alters the sound traveling in a direct path from source to observer. The key difference between obstruction and occlusion is with regard to the impact of the intermediary object on the indirect path of sound. If the indirect path of sound is unaffected by the intermediary object (i.e., the object is small enough that sound travels around it), the sound source is considered obstructed. On the other hand, if the indirect path of sound is affected by the intermediary object (i.e., the object is large enough that the sound is completely blocked), the sound source is said to be occluded. For this paper, occlusion and obstruction will be considered synonymous and only the term occlusion will be used. This stance is taken for three reasons. First, occlusion is the commonly used term visual perception and using that term provides an opportunity to draw comparisons between vision and audition. Second, the term occlusion, as proposed by James J. Gibson (1979), refers to instances when the target of perception is hidden by the interposition of an opaque object. More generally, the term occlusion refers to instances when one object wholly or partially conceals another. The term occlusion, as defined by Gibson, seems more appropriate to the present study. Third, the degree to which indirect sound is impacted by an obstacle is dependent on factors including (but not limited to) impediment size, sound signal frequency, and the distance between the sound source and the impediment. Thus, an object of a particular size could be considered an obstruction in certain instances and occlusion in others. It is the opinion of the authors that the distinction between occlusion and obstruction requires greater discussion and investigation.