Impact of Obstruct Size on the Perceived Occlusion of an Unseen Sound Source

The vast majority of settings inhabited by perceiving-acting organisms are cluttered, and one potential repercussion of clutter is occlusion. As can be imagined, the ability to detect occlusion depends on the size of the piece of clutter. Within certain limits, a direct relationship exists between obstruct size and the likelihood an observer will perceive a target as occluded. The present study examined the extent to which obstruct size influences the ability of individuals to detect sound source occlusion. The obstruct varied in either height, width, or depth, and the task of participants was to indicate whether an object was positioned in front of an unseen sound source. In accordance with previous research, an increase in actual occlusion resulted in an increase in reports of occlusion. Interestingly, an increase in obstruct size did not necessarily result in an enhanced ability to detect occlusion. In fact, reports of occlusion were sometimes unaffected or negatively affected by an increase in obstruct size. The impact of obstruct size appeared to depend on how much the sound source was actually occluded and whether the obstruct changed in height, width, or depth. It was also determined that obstruct area and obstruct volume accounted for less than five percent of the variance in perceptual judgments. Despite the findings of the present, reasons exist for believing the impact of obstruct size on occlusion detection is dependent on factors such as the material composition of the obstruct and the frequency composition of the sound signal.