Edward M. Burns

Ear‐canal impedance and reflection coefficient in human infants and adults

The ear-canal impedance and reflection coefficient were measured in an adult group and in groups of infants of age 1, 3, 6, 12, and 24 months over frequency range 125-10,700 Hz. The development of the external ear canal and middle ear strongly affect input impedance and reflection coefficient responses, and this development is not yet complete at age 24 months. Contributing factors include growth of the area and length of the ear canal, a resonance in the ear-canal walls of younger infants, and a probable influence of growth of the middle-ear cavities. The middle-ear compliance is lower in infants than adults, and the middle-ear resistance is higher. The power transfer into the middle ear of the infant is much less than into that of the adult. Such differences in power transfer directly influence both behavioral and physiological measurements of hearing. The difficulties of interpretation of neonatal tympanograms are shown to be a consequence of ear-canal wall vibration. Impedance and reflectance measurements in the 2-4-kHz range are recommended as a potentially useful clinical tool for circumventing these difficulties.

Intervals, Scales, and Tuning

Publisher Summary The chapter discusses the possible origins and bases of scales including those aspects of scales that are universal across musical cultures. It also addresses the perception of the basic unit of melodies and scales, the musical interval. Natural intervals are define as intervals that show maximum sensory consonance and harmony, have influenced the evolution of the scales of many musical cultures, but the standards of intonation for a given culture are the learned interval categories of the scales of that culture. Based on the results of musical interval adjustment and identification experiments, and on measurements of intonation in performance, the intonation standard for Western music appears to be a version of the equitempered scale that is slightly compressed for small intervals, and stretched for wide intervals, including the octave. The perception of musical intervals shares a number of commonalities with the perception of phonemes in speech, most notably categorical-like perception, and an equivalence of spacing, in sensation units, of categories along the respective continua. However, the perception of melodic musical intervals appears to be the only example of ideal categorical perception in which discrimination is totally dependent on identification. Therefore this chapter concludes that, rather than speech being “special” as ofttimes proclaimed by experimental psychologists it seems that music is truly special.

Prevalence of spontaneous otoacoustic emissions in neonates

The prevalence of spontaneous otoacoustic emissions (SOAEs) was measured in a group of 100 neonates and in a group of 50 normal-hearing young adults. The prevalence of SOAEs in the adult group (0.62) is at the high end of the range of prevalences reported in other surveys of adult SOAEs based on measurements using similar microphones. The prevalence of SOAEs in neonates (0.64) is not significantly different from that in adults. The various tendencies that have been found to be significant in the pooled results of other surveys are also evident in our adult group: more SOAEs in right ears, a higher prevalence of SOAEs in females, and a dependence between ears for the occurrence of SOAEs. The above-mentioned tendencies are also significant in the infant data. The major differences between the infant and adult results are the predominant SOAE frequency range and the average levels of SOAEs. The majority of adult SOAEs are between 1.0 and 2.0 kHz, whereas the majority of neonatal SOAEs are between 2.5 and 5.0 kHz. The average SOAE level is -2.6 dB SPL for adults and 8.5 dB SPL for infants.

Played‐again SAM: Further observations on the pitch of amplitude‐modulated noise

The pitchlike sensation elicited by sinusoidally amplitude‐modulated (SAM) noise remains a controversial phenomenon. The controversy centers on two major points: (1) whether this sensation is ’’really’’ pitch rather than, e.g., roughness or intermittency, and (2) the possibility that any pitch sensation is mediated by short‐term spectral information rather than temporal information—thus nullifying an interesting aspect of the phenomenon. Three experiments employing SAM wideband noise, SAM wideband noise bandpass‐filtered after modulation, and a SAM 10 kHz pure tone were performed: (1) open‐set melody identification, (2) melodic dictation, and (3) musical‐interval adjustment. These experiments extend our earlier study [Burns and Viemeister, J. Acoust. Soc. Am. 60, 863 (1976)]. The results provide further evidence that SAM noise can, at suitable modulation frequencies, elicit a sensation of pitch (as defined by the ability to carry melodic information), and that this pitch represents a purely temporal pheno...

Incidence of spontaneous otoacoustic emissions in children and infants

Whereas some evidence indicates that spontaneous otoacoustic emissions (SOAEs) may be a manifestation of the normal functioning of an active feedback mechanism in the cochlea, other evidence suggests that emissions may be the result of the interaction of such a feedback mechanism with localized outer-hair-cell damage. The present study surveyed the incidence of SOAEs in children and infants. If SOAEs are correlated with outer-hair-cell damage, the incidence of SOAEs might be expected to be lower in these two groups than in adults. The results showed no difference in the incidence of SOAEs with age. They also showed a significant tendency for a higher incidence of SOAEs in females than in males.

Pressure transfer function and absorption cross section from the diffuse field to the human infant ear canal

The diffuse-field pressure transfer function from a reverberant field to the ear canal of human infants, ages 1, 3, 6, 12, and 24 months, has been measured from 125-10700 Hz. The source was a loudspeaker using pink noise, and the diffuse-field pressure and the ear-canal pressure were simultaneously measured using a spatial averaging technique in a reverberant room. The results in most subjects show a two-peak structure in the 2-6-kHz range, corresponding to the ear-canal and concha resonances. The ear-canal resonance frequency decreases from 4.4 kHz at age 1 month to 2.9 kHz at age 24 months. The concha resonance frequency decreases from 5.5 kHz at age 1 month to 4.5 kHz at age 24 months. Below 2 kHz, the diffuse-field transfer function shows effects due to the torsos of the infant and parent, and varies with how the infant is held. Comparisons are reported of the diffuse-field absorption cross section for infants relative to adults. This quantity is a measure of power absorbed by the middle ear from a diffuse sound field, and large differences are observed in infants relative to adults. The radiation efficiencies of the infant and the adult ear are small at low frequencies, near unity at midfrequencies, and decrease at higher frequencies. The process of ear-canal development is not yet complete at age 24 months. The results have implications for experiments on hearing in infants.

Frequency and frequency‐ratio resolution by possessors of absolute and relative pitch: Examples of categorical perception?

The methodology derived from the trace-context theory of intensity resolution (Durlach and Braida, 1969; Macmillan et al., 1988) was applied to resolution over an octave range along two continua: a sequential-frequency-ratio continuum for possessors of relative pitch (RP), and a pure-tone frequency continuum for possessors of absolute pitch (AP). The performance of both RP and AP possessors was exceptional in that total identification sensitivity along both continua was much greater than identification sensitivity along unidimensional psychophysical continua characterized by the 7 +/- 2 rule. In addition, the performance of RP possessors was exceptional in that, on average, total sensitivity for identification resolution was greater than sensitivity for resolution in discrimination. Finally, identification sensitivity between category prototypes (chromatic semits) along both continua was approximately the same as identification sensitivity between phonemic category prototypes along speech continua, despite the fact that both the discrimination ranges and the total number of categories are much larger for the two pitch continua.

Longitudinal measurements of spontaneous otoacoustic emissions in infants

It has previously been shown [E. M. Burns, K. H. Arehart, and S. L. Campbell, J. Acoust. Soc. Am. 91, 1575-1581 (1992)] that both the overall prevalence of spontaneous otoacoustic emissions (SOAEs) and most of the various gender- and ear-related prevalence tendencies are not significantly different in 1-month-olds and adults. However, large differences were found between the neonates and adults in the distributions of the frequencies and levels of SOAEs. Both the average level and the median frequency were significantly higher in infants. To obtain longitudinal SOAE data, infants from this original group of 1-month-olds were tested at ages 3, 6, 12, and 24 months. In general, individual SOAEs decrease in level with age, and high-frequency SOAEs tend to show the largest decreases. No substantial shifts occur in the frequencies of individual SOAEs. The frequency and level distributions at 24 months of age are still not adult-like. SOAEs which show short-term instabilities in frequency and/or amplitude at 1 month of age typically continue to evidence such instabilities at later ages. These results suggest the cochlea is adult-like at birth, and imply that the observed SOAE changes reflect developmental changes in the external and middle ear.

Effects of contralateral acoustic stimulation on spontaneous otoacoustic emissionsa)

Spontaneous otoacoustic emissions (SOAEs) were measured in the ear canal of adult humans prior to, during, and following presentation of tonal and broadband stimuli to the contralateral ear. Tones were presented at a fixed level at ten frequencies relative to the SOAE. Broadband noise was presented at eight levels, from 6 to 76 dB SPL. Shifts in SOAE frequency and amplitude were observed for some subjects, for some tone conditions. Frequency shifts were always positive, whereas amplitude shifts were variable. No apparent pattern of tuning was seen, such that tones with a particular frequency relationship to the SOAEs induced greater changes in the SOAEs. Systematic changes in frequency and amplitude of SOAEs were observed for increasing level of broadband noise for all subjects. Results are discussed with respect to possible mechanism(s) responsible for the alterations in SOAEs: Transcranial conduction; the olivocochlear system; and/or the middle-ear reflex arc.

Suppression tuning curves for spontaneous otoacoustic emissions in infants and adults

Suppression tuning curves (STCs) for spontaneous otoacoustic emissions (SOAEs) were longitudinally obtained in seven infants (at 3 weeks, 2 months, and 3, 4, or 6 months of age) and in five adults. Excellent reproducibility was obtained for adult STCs. Reproducibility for infant STCs was poorer, but the curves at each age resemble those of adults both qualitatively and quantitatively as measured by slopes of the lower and upper segments of the STCs and by Q10s. Evidence from two subjects suggests that developmental changes in the fine tuning of the system may occur postnatally. Results are discussed with respect to the development of cochlear frequency selectivity.