The purpose of this study is to investigate the flow of nonsymbolic auditory information in humans. To achieve this goal the observer adjusts the loudness of a Gaussian noise (GN) signal to match the perceived intensity of an electrodermal stimulus (EDS), a cross-modality matching task. The loudness of the GN and the voltage of the EDS mere maintained within the observer's (O's) sensory probabilistic zone. The sensory probabilistic zone is a range of stimulus intensity from somewhere above "no detection" to "100% detection". The independent variable is a binary condition in that it consisted of catch trials of the time and the remaining time of an EDS at a given intensity (previously determined at an intensity that elicited a response 50% of the time). Consequently, the O's adjustment of the GN reflected his decision-making processes, analysed by signal detection theory and cybernetics. Experiment one demonstrated that neither practice nor the experimenter influenced the O's performance. Also, there are no residual carry-over effects. The 0 has difficulty assigning relative value to the auditory signals and has little or no difficulty in combining, organizing or co-ordinating the auditory information. The second experiment demonstrated that the O's difficulty in assigning relative value to the signals is due to a short memory retention of the nonsymbolic auditory signals (half-life of less than a second). However, verbal confidence ratings (VCRs) add persistency to the auditory memory (echoic memory), its half-life is extended to about 3.1 seconds. The VCR has a half-life of about four seconds. Experiment three demonstrated that nonsymbolic auditory information processing is not affected by interfering signals. From a cybernetic model of the results it is concluded that nonsymbolic auditory information is processed by a filtered, single channel, series processor. Persistency is added to the system's memory component by an interaction between the auditory (echoic) memory and the conceptual symbolic system (VCR).

In the present study, dichotic listening performance of two-year-old children was investigated. Single pairs of words were presented dichoticaly to thirty-one children between GA 2-0-12 and 3-1-20. Each subject was asked to point to pictures of what he had heard. For each pair of words presented, a subject was shown three pictures, which corresponded to the two stimulus words and a foil word. Differences between number of correct responses for each ear were evaluated by means of a t test. Words presented to the right ear were more efficiently recalled than words presented to the left ear, in this age group , which suggests that the left hemisphere has achieved some degree of dominance for language by age two. No statisticaly significant differences were noted, in degree of right ear advantage, between males and females. When studies using school age and adult subjects are compared, it appears that the right ear advantage does not change in magnitude or direction from age two until adulthood. Results of the present investigation are discussed in relation to existing theories of the development of cerebral lateralization. An attempt was made to relate experimental results from dichotic listening,. EEG, and clinical studies. Limitations of the experiment, as wall as suggestions for further research, are discussed. / Medicine, Faculty of / Audiology and Speech Sciences, School of / Graduate

This investigation studies the effect of phonation and of some activities eliciting middle-ear muscle contraction on high-intensity sound transmission in the normal human auditory system. For the most part it is concerned with the influence of phonation on TTS from a continuous pure-tone stimulus. The main experimental technique consisted of measuring subjects' hearing thresholds before and after a 5 min, 500-Hz, 118-dB SPL exposure, this exposure being sometimes accompanied by the performance of a specific activity such as phonation. Threshold tracings were obtained by using a Békésy-type procedure, and threshold was measured at 7 times after cessation of the exposure tone. Analysis of the results indicates that TTS from phonation (humming) during exposure was significantly less than TTS from the exposure tone without any supplementary activity, for a variety of humming activities: humming at 125 Hz (males) or 250 Hz (females); humming loudly at these same frequencies; or humming at 250 Hz (males) or 500 Hz (females). TTS from humming loudly and humming at the higher frequencies was consistently, although not significantly, less than TTS from humming at the lower frequencies. For females, phonation (humming during exposure was more effective in decreasing TTS than for males. Repeatedly turning the head during exposure, which is believed to elicit MEM contraction, resulted in less TTS than no activity during exposure. Similar slight decreases in TTS were observed when the following activities which elicit middle-ear muscle contraction were performed during exposure: chewing, smiling, swallowing. Listening to recorded humming during exposure did not significantly alter TTS from the exposure. The activity of exhaling after preparing to hum did not significantly alter TTS from the exposure. In addition to the TTS studies, measurements of acoustic impedance during the exposure tone and of acoustic reflex thresholds were obtained. Various hypotheses concerning causes for the reduced TTS from phonation during exposure are discussed. Attenuation provided by middle-ear muscle contraction during phonation does not appear sufficient to decrease TTS to the extent that humming does. Sound may be attenuated by inefficient stapes vibration during phonation and TTS may therefore be reduced. Two other possibilities are suggested to account for the TTS decrease: interference between humming and the exposure tone; and interference (by humming) with the central control of middle-ear muscle activity. More evidence will be necessary to satisfactorily determine which, if any, of these mechanisms is actually in effect. / Medicine, Faculty of / Audiology and Speech Sciences, School of / Graduate

The aim of this study was to investigate whether music influences human life before birth. In order to determine the existence and character of music in the uterine acoustic environment, a study was conducted involving the insertion of a hydrophone through the cervix, next to the fetal head. The investigation was conducted on eight women in early labour. The average residual uterine sound of the eight subjects was measured at 65 dBA (A-weighted) re 20 µ.Pa in a 1 O KHz band, RMS averaged over 32-second records. Above this emerged the maternal voice, an external female voice and a male voice presented at approximately 65 dB (linear weighted). Pure tones between 50 Hz and 1 O KHz and orchestral music, all presented at 80 dB (linear weighted), were also shown to emerge above the residual uterine sound. Attenuation of external sound was observed to vary as a function of frequency, with less attenuation of lower frequencies. It was determined that the music was transmitted into the uterus without sufficient distortion to significantly alter the recognisable characteristics of the music. The fetal heart rate (FHA) response to a music stimulus (MS) and a vibroacoustic stimulus (VS) was measured in 40 subjects. Gestational age of the fetuses ranged from 32 to 42 weeks. The study included a control period with no acoustic stimulation; a period with the presentation of 5 music stimuli; and a period with the presentation of 5 vibroacoustic stimuli. A change in the FHA of 15 beats per minute or greater, lasting 15 seconds and occurring within 15 seconds of at least 2 of the 5 stimuli (or a tachycardia of greater than 15 beats per minute above the resting baseline, sustained for one minute or longer) was considered to be a positive response. The MS elicited a positive response in 35 of the fetuses (the 5 non-responses occurring in a period of low FHA variability) and all 40 fetuses responded to the VS (regardless of arousal state). In the third study, mothers attending childbirth education classes volunteered to listen to a prescribed music excerpt twice daily from the 34th week of pregnancy. Ten neonates (all clinically normal) were tested betw~en the 2nd and 5th day after birth. Investigators observed the effect of two music sti:Tiuli, the prescribed stimulus and a non-prescribed stimulus, on neonatal sucking of a non-nutritive nipple. A five-minute control period with no stimulation was compared with a ten-minute period during which two music stimuli were presented. By random allocation, either the prescribed music stimulus (PM) or the nonprescribed music (NM) was presented contingent upon sucking pressure. If a sucking burst was initiated, the PM stimulus was activated. On cessation of sucking, the NM stimulus was activated. Randomly, the procedure would be reversed for some of the subjects, where initiation of sucking activated the NM stimulus and cessation of sucking activated the PM stimulus. It was determined that the inter-burst intervals during the music period were significantly extended when coinciding with the PM stimulus and significantly shortened when coinciding with the NM stimulus.The studies indicated that music is transmitted into the uterus with insufficient distortion to alter the character of the music; that the normal fetus responds to a music stimulus from at least the 32nd week of gestation; and that the neonate alters the normal sucking pattern to activate longer periods of a music stimulus which has been repeatedly presented during the intrauterine stage and shorter periods of a novel music stimulus.

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