Newman Guttman

Lower Limits of Auditory Periodicity Analysis

Tests utilizing an iterated, uninterrupted section of random noise disclose that periodicity (iteration) is easily detectable to about 1 cps and detectable with especial difficulty below 0.5 cps. Frequencies bounding regions of perception of pitch, motorboating, and whooshing are specified as 19, 4, and 1 cps, respectively.

Auditory Nerve: Electrical Stimulation in Man

Auditory perceptions produced in a person deaf to acoustic stimulation were studied by electrically exciting the auditory nerve through permanently implanted electrodes. Pulsed current as small as 1 microampere peak-to-peak could be perceived. Pitch, as reported by the subject, varied with electrode selection, current amplitude, and pulse repetition rate from about 70 to at least 300 pulses per second. Loudness increased with amplitude and duration of pulse stimuli, and to a lesser extent with repetition rate. The total range in amplitude of the stimulus, from threshold to an uncomfortable loudness, was 15 to 20 decibels. Simultaneous stimulation in separate electrodes produced a number of complex effects.

Binaural Interaction of High‐Frequency Complex Stimuli

An experiment is described in which time and intensity differences of 2‐kc high‐pass clicks were mutually offset to produce sound images centered in the head. Binaurally correlated and uncorrelated clicks were used, and the trade was tested at 10–70 db SL. The results show that generally the two types of clicks behave similarly, and that up to 60 db SL, at least, as over‐all intensity increases, the time difference compensating a given intensity difference (in db) decreases. A function is derived describing what is interpreted as a physiological intensity‐to‐time conversion. The place of such a conversion in lateralization is discussed.

On the Pitch of Periodic Pulses

Subjects adjusted the frequency of one periodic pulse train to match the pitch of another train fixed in frequency. Two modes of pitch perception are found. In the first mode, for pulse rates less than 100 pps, the pulse trains are ascribed a pitch equal to the number of pulses per second, regardless of the polarity pattern of the pulses. In the second mode, for fundamental frequencies in excess of 200 cps, the sounds are assigned a pitch equal to the fundamental frequency. Between these frequency regions a mode transition occurs in which the pitch judgments generally fall between the pulse‐rate and fundamental‐frequency values. Amplitude and phase spectra are computed for the stimuli. The stimuli are studied on an electrical analog of the basilar membrane. Waveforms of membrane displacement and first spatial derivative of displacement are obtained from the analog. An effort is made to correlate the psychophysical results with the displacement and derivative patterns observed on the analog membrane. The t...

Width of the Spectrum Effective in the Binaural Release of Masking

In an experiment concerned with the binaural masking‐level difference phenomenon, an attempt was made to determine the extent of the masker spectrum effective in the release of masking. The experiment utilized a uniform power‐spectrum noise separated into two bands differing in interaural phase—an “inner” band surrounding the test signal and “outer” band. Binaural masking‐level differences (BMLDs) were traced as functions of the interaural signal phase (0 and π rad), the relative phase of the bands (0 and π rad), and the bandwidth of the inner band. It was found that a narrow inner band homophasic with respect to signal phase could destroy much of the release of masking owing to the heterophasic outer band. The converse was not true: a wide heterophasic band (125 and 200 cps centered at 250 and 500 cps, respectively) was required to produce significant release. These results depart significantly from predictions of the equalization—cancellation theory of binaural masking and furthermore do not support an assumption that BMLD is a function of the interaural noise crosscorrelation coefficient only.

Exploratory Studies of Zwicker's “Negative Afterimage” in Hearing

This paper describes several exploratory experiments on a subjective tone that Zwicker discovered and referred to as the “negative afterimage.” Zwicker described the tone as audible upon cessation of a band‐rejected noise or band‐rejected pulse train stimulus, and as having a pitch corresponding to a frequency within the rejected band. We worked exclusively with noise stimuli. Our principal finding is that the minimum adequate stimulus appears to be a spectral edge rather than a rejected band, and that a low‐pass edge is more effective than a high‐pass edge. Other findings are as follows. Most people hear the tone, but susceptibility varies widely and the effect is labile. With favorable stimulus parameters, precision of matching to its pitch is on the order of 5% to 10% of the mean. The principal determinant of pitch is the location of the edge of the low‐pass component of the stimulus; the pitch corresponds to a frequency about 23 oct above that edge. Energy in the high‐pass component of the inducing st...

Pitch of High‐Pass‐Filtered Pulse Trains

This experiment determined the pitch of mixed‐polarity pulse trains, high‐pass‐filtered at 2 and 4 kcps. It was found that pitch may be associated with pulse rate at rates higher than the limit of 150 pps found with unfiltered pulses. At frequencies higher than those supporting pulse‐rate pitch, some tendency to hear a pitch equal to the spectral difference frequency appears. Evidence for the difference‐frequency interpretation is the contrast in pitch of patterns equated for pulse number but possessing all‐harmonic and odd‐harmonic spectra. Comparison of the pitch results with a computer simulation of basiliar‐membrane displacements revealed some correlation of difference‐frequency pitch with displacement envelope. It is hypothesized that the high‐pass input‐filter slope combines with the natural‐membrane low‐pass characteristic to form a narrow passband. The envelope of membrane displacement at the passband site tends to contain a pitch‐significant frequency component equal to the difference frequency. ...

Monaural Temporal Masking Investigated by Binaural Interaction

Three experiments were conducted to study monaural temporal masking as manifested in binaural interactions. The experimental paradigm consisted of presenting a pair of clicks in one ear and a single “probe” click in the other. The ability of listeners to bring the probe click into fusion with one or the other contralateral click served as the principal measure of masking. Forward masking (inability to fuse the second click) was studied as a function of repetition rate and click levels. The forward‐masking interval increased with increase of first‐click intensity and, notably, decreased with increase of repetition rate. For the conditions and procedure of this experiment, the longest forward‐masking interval was about 7 msec. Backward masking (inability to fuse the first click) appeared when the monaural clicks were proximate (up to 2 msec in this experiment) and the second click was much more intense than the first. This type of backward masking was deemed a short‐term effect and was distinguished from long‐term backward masking. A model is presented to account for the improved resolution at high repetition rates.

A Mapping of Binaural Click Lateralizations

This experiment principally attempted to map the movements of lateralized auditory images associated with 1‐pps unfiltered clicks heard at two intensity levels and over a wide range of interaural time and intensity differences. With sensation level at 16 db in both ears, lateralization effects were heard for interaural time differences as large as ±15 msec. With 16 db SL in one ear, the minimum level in the other ear producing effects was −6 db, the effect usually being a “bulge” of the image in the audible ear occurring within ±2 msec interaural time difference. Approximately the same time‐difference limits were found, respectively, for 36 db in both ears and 36 db in one ear paired with the minimally effectual −2 db in the other ear. The time‐difference limits within which fusion was “complete” (only one image heard) ranged from 3–7 msec, louder ear leading, to 3 msec, louder ear lagging. It is suggested that the results set a bound on the contribution of direct binaural correlation to the precedence‐ef...

Binaural Interactions of Three Clicks

Listeners tracked the trajectories of auditory images produced by a group of three clicks, of which two were temporally fixed in opposite ears and the third ranged freely in time. The fixed clicks were positioned in three time‐ and level‐difference combinations to produce a centered image. The results indicate that the temporally variable click interferes with the fixed‐clicks image when it leads or lags by as much as approximately 25 msec. The leading interference is plausibly explained by monaural forward masking, but the lagging interference is puzzling, partly because it seems inconsistent with results of other experiments in which the two fixed clicks are in one ear and the variable click is in the other. It was also found that the variable click leading by 5 msec or less completely governs lateralization. It was concluded that monaural forward masking obstructs determination of complex binaural interactions.