Phenomenological Characteristics of the Auditory Stimulus 59 



miles/second. We perceive visual objects because they emit radiant 

 energy or because radiant energy is reflected from them. 



Audible, acoustic energy in space may be considered as a series 

 of condensations and rarefactions of the atmosphere (periodic or 

 aperiodic) that set the peripheral or mechanical portion of the ear in 

 motion which, in turn triggers a series of energy transformations with- 

 in the mechanism. We readily perceive the direction or location of a 

 sound source binaurally but we have less definite information about 

 the size or distance of sound objects in space. Within the human ob- 

 server pitch perception may be viewed as physiological movement in 

 a vertical plane, however, this is not identical with the movement of 

 a sound source in a vertical, spatial dimension. We could extend our 

 descriptions of auditory experiences indefinitely without accounting for 

 the inversion phenomenon mentioned above. 



Theoretical Considerations 



A theory will be presented which depends on an axis of perception 

 concept and is applicable to visual energy travelling in space. This 

 axis is a line from the energy source to the receptor with the energy 

 distributed symmetrically about this axis. This is true whether the 

 energy source is primary, as is a light source, or secondary, as is an 

 object from which light energy rebounds to the receptor. 



The reason we can recognize an inverted visual stimulus but can- 

 not perceive an inverted auditory stimulus may be due to the fact that 

 the light energy reflected by a physical object has many points of 

 reflection and therefore many axes of perception. These reflections 

 form a pattern in a plane perpendicular to their axis of perception and 

 as a consequence have an additional axis in that plane; an axis of 

 symmetry normal to the axis of perception. We detect inversion only 

 if there are differences between the energy sources. If a flawless cir- 

 cular surface were presented visually and rotated before a subject, 

 he would not detect the rotation. An inverted circular disk with an 

 uneven surface, properly illuminated, would create an axis of symmetry 

 and rotation of this axis about the axis of perception would permit its 

 recognition as an inverted visual object. 



In the auditory realm, we can produce a complex of sounds, each 

 with a different source; such as a central loudspeaker rimmed by a 

 series of satellite speakers. In this situation we would detect the ro- 

 tation of each individual source about the mean axis of perception 

 even though we could not detect the rotation of each individual sound 

 source about its own axis of perception. In audition, we perceive what 



