Oldfield, S. R., and S. P. A. Parker. (1984b). "Acuity of Sound Localization: A Topography of Auditory Space. II. Pinna Cues Absent." Perception 13 (1984b): 601--617.

Oldfield, S. R., and S. P. A. Parker. (1986). "Acuity of Sound Localization: A Topography of Auditory Space. III. Monaural Hearing Conditions." Perception 15 (1986): 67--81.

These three studies examine the ability of subjects under different sets of conditions to localize white noise played through a speaker that varied in position. The blindfolded subjects pointed a special gun at the perceived source of sound played in an anechoic chamber over a boom-mounted speaker. In the first study subjects listened normally; in the second study pinna cues were removed by inserting individually cast pinnae molds with access holes to the auditory canal into subjects' ears; and in the third study monaural conditions were created by inserting "ear defenders" into subjects' right ears and covering their right ears with fitted earmuffs. These studies demonstrate the importance of pinna cues for determining elevation and reducing front/back reversals, and show that elevation discrimination was good under monaural conditions, but that azimuth discrimination was reduced.

O'Leary, A., and G. Rhodes. "Cross-Modal Effects on Visual and Auditory Object Perception." Percep. & Psycho. 35 (1984): 565--569.

Using a display that combined a stimulus for auditory stream segregation with its visually apparent movement analog, these Stanford University researchers demonstrated cross-modal influences between vision and audition on perceptual organization. Subjects hearing the same auditory sequence perceived it as two tones if a concurrent visual sequence was presented that was perceived as two moving dots, and one tone if a concurrent visual sequence perceived as a single object was presented.

Oppenheim, Alan V., ed. Applications of Digital Signal Processing. ISBN 0-13-039115-8. Prentice Hall, 1978.

Collection of papers on DSP applications, A couple of chapters are dedicated to processing audio signals and speech. The rest is exotic (RADAR, SONAR, Geophysics) and there is one chapter on digital image processing.