John A. Rupf

Speech‐Synchronized versus Periodic Interaural Switching of Speech

The ability of subjects to “shadow” speech switched between the ears periodically was compared to that for speech switched in syllable and phoneme units. Shadowing performance, expressed in terms of incorrectly articulated words, was not significantly different for the two conditions under test.

A method for the precise switching of speech

A simple procedure by which a speech signal may be switched on or off (or from one ear to the other) at a precise instant of time is described. The speech sample is first recorded on a magnetic tape loop. A reference pulse is then recorded preceding the speech signal. This reference pulse triggers an adjustable time delay which in tum operates an electronic switch at an appropriate time.

A test of precategorical acoustic storage for vowels

A common element among several proposed speech perception models is that an acoustic representation of the speech signal persists briefly in memory prior to phonetic processing. It is also commonly hypothesized that with the passage of time the auditory signals are degraded. These hypotheses were tested in a perceptual experiment in which subjects were presented short segments of vowels for identification. A single glottal pulse from each of the vowels /ɑ, i, I, ae, e,/ was excised from natural speech and repeated to produce three types of stimuli: two contiguous glottal pulses, four contiguous glottal pulses, and two contiguous glottal pulses followed by two more contiguous glottal pulses with interspersed silences of 10, 20, 40, 60, 80, 120, 240, 480, 1000, and 2000 ms. The stimuli for all vowels and types were randomized and presented to subjects. As expected, the four contiguous glottal pulse stimuli gave better recognition scores than the two contiguous glottal pulse stimuli. It was predicted that as ...

Context effects on silent interval estimation in speech and nonspeech environments

The speech stimuli for this experiment were derived from two sentences, each containing the words free criminals. In one sentence, the words free criminals occurred intraphrase and in the other sentence they occurred interphrase. The vowel duration in free and the silent interval preceding criminals were systematically and independently varied. Vowel durations of 100, 200, 300, 400, 500, and 600 msec were paired with silent intervals of 0, 50, 100, 150, 250, and 500 msec. Subjects were asked to make direct magnitude estimates of the silent interval duration between free and criminals. Power‐law scaling exponents for judgments versus vowel duration and silent interval duration were 0.29 and 0.48, respectively. The above experimental procedure was repeated in two experiments using nonspeech stimuli with temporal characteristics similar to the two sentences. In particular, the silent interval to be estimated occurred between two 1000‐Hz tones. In Experiment 1 the duration of the tone preceding the silent int...

Silent Interval and Vowel Duration Effects on Pause Magnitude Estimation in Intrapause and Interpause Environments

The stimuli for this experiment were derived from two sentences, each containing the words free criminals. In one sentence these two words occurred within a phrase, and in the other sentence a phrase boundary occurred between the words. The vowel duration in free and the silent interval preceeding criminals were systematically and independently varied. Vowel durations of 100, 200, 300, 400, 500, and 600 msec were paired with silent intervals of 0, 50, 100, 150, 250, and 500 msec for both sentences. Subjects were asked to make direct magnitude estimates of the perceived pause between free and criminals in each of the stimulus sentences. Results indicated that given durations of vowel and silent interval result in similar perceived pauses in intraphrase position than in interphrase position. Power law scaling exponents were larger for vowel duration than for silent interval in all conditions. [This research supported by the National Institutes of Health.]

Effect of Interaural Switching on the Recognition of Speech Sounds

The intelligibility of nonsense syllables was investigated as a function of the place in the speech waveform where the signal was switched from one ear to the other. The results demonstrated that the place at which switching occurred had essentially no effect on the identification of either the consonants or the vowels in the stimuli. In view of these findings it is unlikely that phonological rules are applied before the signals to the two ears are combined in the auditory system.

Temporal‐Order Perception of Vowel Sequences with Monaural and Binaural Presentation

The ability of subjects to repeat alternated speech depends on the alternation rate. The possibility that alternation interferes with the perception of temporal order was investigated in an experiment in which subjects determined the temporal order of vowel sequences under monaural and binaural conditions of presentation. Test stimuli were formed from segments of the vowels /i, ɛ, a, u/. Each stimulus consisted of four equal segments of the four vowels arranged in a random order. Segment duration was varied from 300 to 50 msec. For half the stimuli, the vowels were contiguous and presented to one ear, while for the remainder of the stimuli adjacent vowels were presented to opposite ears. On a given trial, using either the monaural mode or the binaural modes, the ability of subjects to determine the vowel order decreased monotonically with segment duration. Performance varied from near perfect with 300 msec segments to near chance with 50 msec segments. Performance with binaural stimuli was consistently lo...

Perception of Linguistic Boundaries

The necessity for segmentation in linguistic descriptions of an utterance has long been recognized. We have made a study of the perception of boundaries between phonemic segments of natural speech. Subjects were instructed to divide an utterance at the boundary between a consonant and vowel by causing the presentation (under phones) to switch from one ear to the other at a point in time corresponding to the CV or VC boundary. The means and variances of these subjective placements were measured and, intersubject variation was found to be greater than intrasubject variation, but both were large. Subjective boundaries seldom corresponded to prominent waveform features visible on a CRO. Subjective boundaries determined by switching were compared to subjective boundaries determined by listening to gated segments. [This work was supported in part by the Air Force Cambridge Research Laboratories under Contract.]

Further Studies of the Intelligibility of Alternated Speech

Previous studies in which subjects were asked to repeat (i.e., shadow) speech that was switched alternately between the two ears have presented evidence that the perception of alternated speech is adversely effected when alternation is synchronous with syllables [A. W. F. Huggins, J. Acoust. Soc. Am. 36, 1055–1064 0964); G. W. Hughes et el., J. Acoust. Soc. Am. 40, 1283 (1966)]. In this study, we compare the perceptual effects of syllable‐synchronous switching to those caused by alternation that occurs periodically at the average syllable rate. We also compare effects of alternation at phoneme boundaries with the effects of other conditions of alternation. No striking difference in shadowing performance between the syllable‐ or phoneme‐locked alternation and the periodic alternation were observed, but a strong patterning of errors relative to position in the script was found for all modes of alternation. Our results indicate that script composition may be a more important factor than mode of alternation i...