Papers on monaural localization relating to the action of the vestibular apparatus, influence of the auricle, and movements of the head were reviewed. To test one conclusion of the review, that a moving sound source should yield a continuous set of changing loudness/phase/timing cues available to the ear, an experiment was conducted which provides more complete quantification of monaural/binaural comparison. Minimum audible angles (maa) were computed from the responses of three men, highly experienced in listening, to white noise and tones produced by a moving sound source. The men listened (1) with both ears open, and (2) with one ear plugged, muffed, and noise-masked. The monaural maa at 0° and 60° az were as good as the binaural maa for white noise, and for the lowest tone at 0° az, but distinctly inferior elsewhere. Both azimuth and monaural/binaural mode effects reached high significance statistically. The data show much usable directionality for the monaural mode.

Responses to glissando at 1500 cps at a 50-phon level using trained and untrained listeners are analyzed. The sensitivity to this type of frequency modulation is surprisingly good. A constant of 5 cps change emerges indicating that sensitivity depends on a linear relationship between rate of change and stimulus duration. This constant is of the same order of magnitude as the traditional DL for pitch memory. The low observed relationship of glissando to either pitch discrimination by the constants method or with sensitivity to the presence or absence of sinusoidal frequency modulation indicates that probably a third distinct pitch factor is represented.

Eight subjects trained in listening were given a variety of taped programs of frequency glissando consisting of items which began at 1500 cps and proceeded at 50 phons either up or down in frequency. S's were required to judge “higher” or “lower.” Periods of glissando from 0.2 to 10 sec and rates of change from 0.5 to 100 cps/sec were used. Sensitivity to this type of frequency modulation is surprisingly good, and inter-subject variation is not excessive; thus it could well form one sensory input to certain man-machine systems, either on an absolute or a relative basis. One S, extremely poor on the more usual pitch test by the constants method, was not much worse than average on glissando. For most S's, a constant emerges at a total of about 5-cps change, such that sensitivity to 0.5 cps/sec change over 10 sec is about equally as difficult as 5 cps/sec change over 1 sec, and so on. This constant is in fact of the same order of magnitude as the traditional DL for pitch.

This study was designed to evaluate the effect of rate (68, 127, 180 words/min) and intensity (20, 40, 60 SRT) of stimulus presentation, and of practice, upon concurrent repetition of a continuous flow of heard words. Subjects were 33 enlisted men. A three-part tape was made to obtain an SRT, to present a pretest trial, and to present three PB-50 lists read as continuous speech. Intelligibility scores were assigned to each subject's taped repetitions. Twelve subjects had an 8-day practice with other PB lists. Analysis of variance yielded an F associated with practice significant beyond the 0.5% level. The F's for rate and intensity were significant beyond the 0.1% level. Pearson r's were calculated between performance level and six psychological and auditory tests. Only the r of +0.54 with the Seashore Rhythm test was significant. It was concluded that: (a) Performance improves with increased intensity of heard speech, and with practice; (b) Performance increases when the rate of stimulus presentation is decreased; (c) A positive relationship exists between performance and scores on the Seashore Rhythm test; (d) Under proper conditions of rate and intensity, some persons can be trained to perform with more than 90% intelligibility.

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