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PubMed1992

Some new pitch paradoxes and their implications.

This paper explores two new paradoxical sound patterns. The tones used to produce these patterns consist of six octave-related harmonics, whose amplitudes are scaled by a bell-shaped spectral envelope; these tones are clearly defined in terms of pitch class (C, C#, D, and so on) but are poorly defined in terms of height. One pattern consists of two tones that are separated by a half-octave. It is heard as ascending when played in one key, yet as descending when played in a different key. Further, when the pattern is played in any one key it is heard as ascending by some listeners but as descending by others (the tritone paradox). Another pattern that consists of simultaneous pairs of tones displays related properties (the semitone paradox). It is shown that the way the tritone paradox is perceived correlates with the speech characteristics of the listener, including his or her linguistic dialect. The findings suggest that the same, culturally acquired representation of pitch classes influences both speech production and also perception of this musical pattern.

Acoustic Stimulation↗
PubMed1980

On tune deafness (dysmelodia): frequency, development, genetics and musical background.

With the aid of the Distorted Tunes Test a group of British adults could be established whose melodic aptitude was below a certain level and whom we called tune deaf. They are only a fraction of those popularly called tone deaf. The Distorted Tunes Test is only slightly correlated with pitch discrimination, short term tonal memory or number memory. In children ability to pass the Distorted Tunes Test develops at greatly varying speeds and to a varying degree, reaching stability in adolescence. Tune deafness has a familial distribution and segregates in a way suggesting an autosomal dominant trait with imperfect penetrance. Some degree of positive assortative mating has been established. Some people, unfamiliar with the British melodies which form the basis of the test, pass it. This indicates the existence of a partly innate and partly acquired competence to judge what is acceptable and what is not, within the tradition of Western popular or classical music. This seems to indicate the existence of some deep structure of tonality, comparable with Chomsky's deep language structure. Asians who have not been much exposed to this kind of music find the task very difficult.

Adolescent↗
PubMed1995

Brain event-related potentials to complex tones in depressed patients: relations to perceptual asymmetry and clinical features.

Brain event-related potentials (ERPs) to probe tones in a dichotic complex tone test were recorded from right-handed depressed patients (n = 44) and normal subjects (n = 19) at homologous sites over left and right hemispheres (F3, F4; C3, C4; P3, P4; O1, O2). There were no differences between groups N1 or P2 amplitude, but patients had smaller P3 amplitude than did normal subjects. Depressed patients failed to show either the left ear advantage or behavior-related hemispheric asymmetry of P3 seen for normal subjects. Depressed patients also showed less difference in hemispheric asymmetry between same and different judgments. These findings indicate that the abnormal behavioral asymmetry for dichotic pitch discrimination in depressed patients reflects a reduction in hemispheric asymmetry and is related to relatively late stages of cognitive processing.

Acoustic Stimulation↗
PubMed1989

Extracochlear electrical stimulation.

Twelve patients with sensorineural hearing loss were stimulated by a transtympanic electrode contacting the cochlear promontory. Nine of them were tested to study hearing perception associated with various features of electrical signals, using an auditory electrical stimulator. Biphasic pulse bursts and sine-wave bursts were used as stimuli. Different electrical characteristics such as amplitude, width and rate for pulses and amplitude and frequency for sine waves were used to investigate hearing perception. The patients' perception threshold, comfortable level, uncomfortable level, dynamic range, just-noticeable difference in frequency or pitch discrimination, just-noticeable difference in intensity or loudness discrimination, loudness perception associated with the electrical signal energy, and sounds associated with electrical stimulation was determined. Pertinent results assisted in the development of a speech electrical stimulator that was used to test three patients for vowel, word, and consonant identification and recognition of patterns of intonation. These results in turn are being used to design a prototype of a single-channel extracochlear prosthesis.

Acoustic Stimulation↗
PubMed2002

Spectro-temporal processing in the envelope-frequency domain.

The frequency selectivity for amplitude modulation applied to tonal carriers and the role of beats between modulators in modulation masking were studied. Beats between the masker and signal modulation as well as intrinsic envelope fluctuations of narrow-band-noise modulators are characterized by fluctuations in the "second-order" envelope (referred to as the "venelope" in the following). In experiment 1, masked threshold patterns (MTPs), representing signal modulation threshold as a function of masker-modulation frequency, were obtained for signal-modulation frequencies of 4, 16, and 64 Hz in the presence of a narrow-band-noise masker modulation, both applied to the same sinusoidal carrier. Carrier frequencies of 1.4, 2.8, and 5.5 kHz were used. The shape and relative bandwidth of the MTPs were found to be independent of the signal-modulation frequency and the carrier frequency. Experiment 2 investigated the extent to which the detection of beats between signal and masker modulation is involved in tone-in-noise (TN), noise-in-tone (NT), and tone-in-tone (TT) modulation masking, whereby the TN condition was similar to the one used in the first experiment. A signal-modulation frequency of 64 Hz, applied to a 2.8-kHz carrier, was tested. Thresholds in the NT condition were always lower than in the TN condition, analogous to the masking effects known from corresponding experiments in the audio-frequency domain. TT masking conditions generally produced the lowest thresholds and were strongly influenced by the detection of beats between the signal and the masker modulation. In experiment 3, TT masked-threshold patterns were obtained in the presence of an additional sinusoidal masker at the beat frequency. Signal-modulation frequencies of 32, 64, and 128 Hz, applied to a 2.8-kHz carrier, were used. It was found that the presence of an additional modulation at the beat frequency hampered the subject's ability to detect the envelope beats and raised thresholds up to a level comparable to that found in the TN condition. The results of the current study suggest that (i) venelope fluctuations play a similar role in modulation masking as envelope fluctuations do in spectral masking, and (ii) envelope and venelope fluctuations are processed by a common mechanism. To interpret the empirical findings, a general model structure for the processing of envelope and venelope fluctuations is proposed.

Adult↗
PubMed2004

High-frequency electromotile responses in the cochlea.

Mammalian outer hair cells (OHCs) convert electrical energy into mechanical energy. The significance of this electromotility rests in the ability of the OHCs to modulate the vibrations of the cochlear partition in vivo. While high-frequency electromotility of isolated OHCs has been demonstrated at frequencies up to 100 kHz, a similar measure of the effect of OHC electromotility on motion of the sensory epithelium has not been made in vivo. In this study, in vivo electrical stimulation of the guinea pig cochlea is found to induce a mechanical response of the basilar membrane for frequencies to at least 100 kHz, nearly twice the upper limit of hearing for the guinea pig. The perfusion of salicylate in the cochlea reversibly reduces the electromotile response, indicating that an OHC-mediated process is the key contributor.

Acoustic Stimulation↗
PubMed2005

Dead regions and pitch perception.

The perception of pitch for pure tones with frequencies falling inside low- or high-frequency dead regions (DRs) was examined. Subjects adjusted a variable-frequency tone to match the pitch of a fixed tone. Matches within one ear were often erratic for tones falling in a DR, indicating unclear pitch percepts. Matches across ears of subjects with asymmetric hearing loss, and octave matches within ears, indicated that tones falling within a DR were perceived with an unclear pitch and/or a pitch different from "normal" whenever the tones fell more than 0.5 octave within a low- or high-frequency DR. One unilaterally impaired subject, with only a small surviving region between 3 and 4 kHz, matched a fixed 0.5-kHz tone in his impaired ear with, on average, a 3.75-kHz tone in his better ear. When asked to match the 0.5-kHz tone with an amplitude-modulated tone, he adjusted the carrier and modulation frequencies to about 3.8 and 0.5 kHz, respectively, suggesting that some temporal information was still available. Overall, the results indicate that the pitch of low-frequency tones is not conveyed solely by a temporal code. Possibly, there needs to be a correspondence between place and temporal information for a normal pitch to be perceived.

Acoustic Stimulation↗
PubMed1983

Do off-frequency simultaneous maskers suppress the signal?

Psychophysical tuning curves obtained in forward masking show greater tuning than those obtained in simultaneous masking. This difference is often attributed to the contribution of suppression to the masking produced by off-frequency simultaneous maskers. In this experiment, simultaneous-masking tuning curves were obtained using a 195-ms, 1-kHz sinusoidal signal presented at 40 dB SPL. If the maskers identified in this procedure reduce signal detectability by suppressing the response to the signal, then it should be possible to demonstrate suppression effects between stimuli with the parameters of the masker and signal. One conventional method for demonstrating suppression is to show a reduction in the amount of forward masking produced by one stimulus when a second stimulus is added to it. When used to test the effect of the masker upon the signal, this procedure does not show the suppression supposedly produced by the off-frequency maskers. These data are consistent with an alternative explanation involving only excitatory interactions between masker and signal.

Adult↗
PubMed1983

Lateralization based on interaural phase differences: effects of frequency, amplitude, duration, and shape of rise/decay.

Experiments in lateralization were performed to evaluate the relative contribution of envelope and phase cues in binaural hearing with particular reference to the effects of frequency, amplitude, shape of rise/decay, and duration of peak amplitude. Pure-tone signals were presented with interaural phase shifts ranging between 90 degrees and 360 degrees. For a given value of phase shift, the leading signal was presented randomly to the right or left ear over a block of 100 trials, and the laterality of the resultant image was judged. Rise/decay time was varied from 5 to 200 ms across blocks. The results confirmed our previous finding that a rise/decay time of at least 200 ms is required to secure a psychophysically steady-state signal. This value will, however, depend on the values chosen for the other signal parameters. Within limits, decreasing intensity could be compensated for by decreasing rise/decay, suggesting the psychophysical importance of the initial segment of the signal (precedence effect). For low frequencies of 650 to 1250 Hz, performance is sensitive to interaural phase shift and largely independent of frequency. For higher frequencies of 1500 and 2000 Hz, lateralization is independent of the phase cue and also largely insensitive to change in rise/decay time. Finally, performance remains unchanged with variation in peak duration ranging from 25 to 200 ms.

Dominance, Cerebral↗
PubMed1983

Pure tone pitch perception and low-frequency hearing loss.

Pitch perception for pure tones was investigated in a group of listeners with low-frequency sensorineural hearing loss. Pitch judgments from each listener were compared with results from psycho-acoustic tasks which provide information on the "place" of cochlear response. The pitch measures employed were: (1) binaural pure-tone pitch matching in a listener with unilateral hearing loss, (2) octave judgments in listeners with musical ability, and (3) pitch-intensity functions in other listeners. Cochlear place of response was inferred from psychophysical tuning curves (PTC's). Two distinct types of PTC's for low-frequency probe tones were observed. Three listeners demonstrated "abnormally tuned" PTC's. For these listeners the frequencies that were most effective at masking the probe were considerably higher than the probe frequency. The three remaining listeners demonstrated "normally tuned" PTC's. Listeners with abnormally tuned PTC's were suspected of having an extremely abnormal place of response for low-frequency tones; this response pattern being located more toward the base of the cochlea than in the listeners with normally tuned PTC's. Sensitivity thresholds measured in the presence of high-pass masking noise supported this hypothesis. Small pitch-frequency irregularities were observed in many listeners, although they were not consistently related to the inferred place of response for that frequency. The individual listeners' pitch judgments failed to distinguish between two types of PTC's. In particular, listeners who demonstrated abnormally tuned PTC's did not exhibit correspondingly large pitch irregularities. These results are difficult to explain on the basis of a classical "place" theory of pitch perception.

Adult↗
PubMed1984

Temporal gap resolution in masked normal ears as a function of masker level.

Recent studies of temporal resolution in hearing-impaired listeners indicate that many ears with cochlear damage exhibit elevated temporal gap thresholds. The deviations from normal may be large, for equivalent-SPL comparisons, but are often small or absent for equivalent-SL comparisons. In the present experiment, we examine the premise that SL effects in gap resolution are independent of sound pressure level. Normal hearing subjects used a Békésy procedure to track the minimum level of an octave-band signal at 1 kHz needed to keep a periodic temporal gap at threshold. Performance functions were generated to show stimulus intensity as a function of gap duration, for gaps from 25 ms to the smallest detectable value. In separate conditions, the level of a white-noise background was varied to shift the subject's audibility threshold. Results indicate that the limits of resolution are largely invariant with SPL, but criterion sensation levels for resolution are progressively reduced at higher SPL. It is concluded that gap thresholds from normal and impaired ears should be compared for equivalent SPL; comparisons made with SL equated are likely to underestimate the consequence of cochlear damage on resolving capacity.

Audiometry, Pure-Tone↗
PubMed1984

Interaural time sensitivity of high-frequency neurons in the inferior colliculus.

Recent psychoacoustic experiments have shown that interaural time differences provide adequate cues for lateralizing high-frequency sounds, provided the stimuli are complex and not pure tones. We present here physiological evidence in support of these findings. Neurons of high best frequency in the cat inferior colliculus respond to interaural phase differences of amplitude modulated waveforms, and this response depends upon preservation of phase information of the modulating signal. Interaural phase differences were introduced in two ways: by interaural delays of the entire waveform and by binaural beats in which there was an interaural frequency difference in the modulating waveform. Results obtained with these two methods are similar. Our results show that high-frequency cells can respond to interaural time differences of amplitude modulated signals and that they do so by a sensitivity to interaural phase differences of the modulating waveform.

Animals↗
PubMed1985

The role of suppression in psychophysical measures of frequency selectivity.

The neural output of the cochlea consists of a structured spectral representation of the input waveform. Psychophysical studies of frequency selectivity provide measures of the quality of this spectral representation based on the detection of a spectrally narrow signal in the presence of competing acoustic inputs. Results are often interpreted in terms of the underlying physiological processes. The present paper begins with a summary of the basic principles and data and a review of recent efforts to extend the theoretical framework to account for a wider range of phenomena. It then discusses and evaluates specific assumptions concerning the role of suppression in psychophysical measures of frequency selectivity, an area of research that has received much attention in recent years. The goal is to provide a summary of current answers to basic questions at a time of rapidly expanding knowledge about both the physiology and psychophysics of frequency selectivity.

Animals↗
PubMed1986

Rate responses of auditory nerve fibers to tones in noise near masked threshold.

The rate responses of auditory nerve fibers were measured for best frequency (BF) tone bursts in the presence of continuous background noise. Rate functions for BF tones were constructed over a 32-dB range of levels, centered on the behavioral masked thresholds of cats. The tone level at which noticeable rate changes are evoked by the tones corresponds closely to behavioral masked threshold at all noise levels used (-10- to 30-dB spectrum level). As the noise level increases, the response rate to the background noise approaches saturation, and the incremental rate response to tones decreases. At high noise levels, the rate responses to tones of low and medium spontaneous rate fibers are larger than those of high spontaneous rate fibers. Empirical statistics of auditory nerve fiber spike counts are reported; these differ from those expected of a Poisson process in that the variance is smaller than the mean. A new measure of discharge rate is described that allows rate changes to be expressed in units of a standard deviation. This measure allows tone-evoked responses to be interpreted in terms of their detectability in a signal detection task. Rate responses of low and medium spontaneous rate fibers are more detectable than those of high spontaneous rate fibers, especially at high noise levels. There appears to be sufficient information in the rate response of a small number of auditory nerve fibers to support behaviorally observed levels of detection performance.

Acoustic Stimulation↗
PubMed1986

The effect of across-frequency differences in masking level on spectro-temporal pattern analysis.

Masking noise well separated in frequency from the signal may improve the detectability of the signal if the masking noise is modulated. This effect is referred to as co-modulation masking release (CMR). The present experiments examine the effect of across-frequency differences in masking noise level on CMR. Three experiments were performed, each using a different method to create modulated noise stimuli having across-frequency differences in the spectrum level. All stimulation was monaural. Experiment I used a notched noise method (selectively reducing the level for the critical band centered on the signal). Experiment II used a method in which the level of a 100-Hz-wide masker centered on the signal was varied, and flanking noise bands were of constant level. Experiment III used a method in which flanking noise bands were varied in level, and the 100-Hz-wide masker centered on the signal was of constant level. The signal was a 1000-Hz, 300-ms pure tone. The CMR effect was negated by small spectral notches centered on the signal (experiment I). However, CMR proved to be relatively robust to across-frequency level differences in experiments II and III (a CMR effect occurred for across-frequency differences in spectrum level as great as 20 dB). Low CMR's obtained in experiment I were probably due to relatively poor correlation of across-frequency modulation pattern which occurred with notched noise. The results of experiments II and III suggest that the fluctuation pattern is of primary importance in providing release from masking, and that information on absolute levels, coded across frequency, is of less importance.

Adult↗
PubMed1987

Perceptual organization of complex-tone sequences: a tradeoff between pitch and timbre?

Sequences of rapidly occurring sounds that differ from each other are often perceptually segregated into "streams" within which the range of differences is smaller [Bregman and Campbell, J. Exp. Psychol. 89, 244-249 (1971)]. Early research on streaming implied it to be pitch dominated, but Wessel [Comput. Music J. 3, 45-52 (1979)] demonstrated that timbre differences could also bring about segregation. In the present study, pitch and timbre attributes were put in competition in four-tone sequences of the form: T2P1-TmP1-T2Pn-TmPn, with the first pair assigned pitch P1 but different timbres T2 and Tm, and the second pair pitch Pn, and similarly contrasted timbres. Six listeners were asked to indicate whether perceived grouping of 49 such sequences was based on pitch proximity, timbre similarity, or ambiguous percepts not dominated by either cue. Results confirm that timbre can segregate sequences and imply that timbre and pitch compete in perceptually organizing complex sequences. Because timbre differences were provided by varying the locus of four equal-amplitude harmonics, and pitch differences were provided by varying their relative spacing, it is suggested that the tradeoffs observed may actually arise due to differences in perceived salience of "spectral pitch" and "virtual pitch" [Terhardt, J. Acoust. Soc. Am. 55, 1061-1069 (1974)] dependent on relative changes in spectral locus and spectral spacing over time.

Adult↗
PubMed1991

Spectral cues to perception of /d, n, l/ by normal- and impaired-hearing listeners.

The alveolar consonants /d, n, l/ occur frequently in intervocalic position in conversational speech but have received little study for differences in their acoustic cues. Impaired- and normal-hearing listeners were investigated for use of consonant-segment versus transition-segment cues to recognition of /d, n, l/ in /aeCae/ tokens extracted from sentences. To examine the cues' contribution to /d, n, l/ recognition, the segments were degraded singly or in combinations in the tokens as follows: [aeC] or [Cae] transitions were replaced by adjacent pitch periods from the respective vowels; the consonant segments were replaced by silence or by a synthetic consonant approximating the summed low-frequency spectra of the /d, n, l/ murmurs. The results with normal-hearing listeners showed that the presence of any one of the three segments, [aeC] transition, [Cae] transition, or natural consonant segment, supported a moderate to high level of /d, n, l/ recognition, depending on the phoneme. In contrast, the severely hearing-impaired listeners' consonant recognition was poor on the basis of transition information, but better in the presence of the natural consonants. The /aeCae/'s with the synthetic consonant yielded chance level performance for the hearing-impaired listeners but good consonant recognition for the normal-hearing listeners--a further indication that cues in the transitions were quite useful for the normal-hearing group but not for the hearing-impaired group.

Adult↗