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PubMed1989

Auditory discrimination of tone-pulse onsets.

Two experiments are reported in which difference limens (DLs) were measured for onset times of a 1000-Hz tone pulse. An adaptive two-alternative forced-choice procedure and (mostly) well-trained subjects were used. In the first experiment, DLs were measured for the rise time of linear onset ramps at rise-time values between 10 and 60 msec. The DLs follow Weber's law up to a rise time of about 50 msec, and do not support the notion that rise times are perceived in a categorical manner. In the second experiment, DLs were obtained for linear, exponential, and raised-cosine onset envelopes at rise-time values between 10 and 40 msec. When energy differences in the critical band around 1000 Hz are computed for just-discriminable onsets, values between 0.7 dB (10-msec rise time) and 0.3 dB (40-sec rise time) are found. These equivalent intensity DLs show the same "near miss to Weber's law" behavior as do intensity DLs for pure tones.

Attention↗
PubMed1983

Discrimination of speech processed by low-pass filtering and pitch-invariant frequency lowering.

Consonant discriminability by normal-hearing listeners was studied for monosyllables processed using frequency lowering with either uniform (linear) or nonuniform (warped) compression of the frequency axis. The bandwidth of the compressed signal was either 2500 or 1250 Hz and five compression characteristics were studied, in addition to low-pass filtering, for each of the two bandwidths. Stimuli were 24 consonant-vowel syllables made up of 24 consonants and three vowels, recorded three times by each of two male and female speakers. A "roving-speaker, roving-vowel, roving-utterance," two-interval, forced-choiced procedure with feedback was employed. As expected, performance for the 2500-Hz bandwidth was superior to that for the 1250-Hz bandwidth. For each bandwidth, compression schemes which accomplished greater lowering of the high frequencies relative to the low frequencies resulted in the highest performance. Overall performance for the best frequency-lowering system studied, however, was roughly comparable to that obtained for low-pass filtering. Patterns of performance over articulatory features were different for frequency lowering and filtering. In general, lowering was superior to filtering for contrasts of fricative sounds but inferior for contrasts of nasals and semivowels.

Female↗
PubMed2005

Frequency discrimination and literacy skills in children with mild to moderate sensorineural hearing loss.

It has been suggested that specific reading disability (SRD) may be attributable to an impaired ability to perceive spectral differences between sounds that leads to a deficit in frequency discrimination and subsequent problems with language and literacy. The objective of the present study was three-fold. We aimed to (a) determine whether children with mild to moderate sensorineural hearing loss were impaired in their ability to discriminate frequency, (b) assess the extent to which any such deficits may be due to an inability to use information derived from phase locking, and (c) examine whether frequency discrimination abilities were predictive of measures of word and nonword reading and nonword repetition. Difference limens for frequency (DLFs) were obtained for 22 children with mild to moderate hearing loss (SNH group) and 22 age-matched controls (CA group) at central frequencies of 1 kHz, where phase-locking information is available, and 6 kHz, where it is not. A battery of standardized tests of language and literacy was also administered. The SNH group exhibited significantly elevated DLFs at both 1 and 6 kHz relative to controls, despite considerable variability of thresholds in both groups. Although no group differences were found for receptive and expressive vocabulary, receptive grammar, and nonword reading, the SNH group performed worse than controls on word reading and nonword repetition, even though word reading scores were age-appropriate. Frequency discrimination abilities were associated with reading and nonword repetition across groups, but these correlations largely disappeared when the two groups were analyzed separately. Together, these results provide evidence for a dissociation between impaired frequency discrimination and relatively "spared" language and literacy in children with mild to moderate sensorineural hearing loss. These results cast doubt on the assertion that a deficit in frequency discrimination necessarily leads to marked deficits in the development of language and literacy.

Adolescent↗
PubMed1991

Discrimination of formant transition onset frequency: psychoacoustic cues at short, moderate, and long durations.

Two experiments determined the just noticeable difference (jnd) in onset frequency for speech formant transitions followed by a 1800-Hz steady state. Influences of transition duration (30, 45, 60, and 120 ms), transition-onset region (above or below 1800 Hz), and the rate of transition were examined. An overall improvement in discrimination with duration was observed suggesting better frequency resolution and, consequently, better use of pitch/timbre cues with longer transitions. In addition, falling transitions (with onsets above 1800 Hz) were better discriminated than rising, and changing onset to produce increments in transition rate-of-change in frequency yielded smaller jnd's than changing onset to produce decrements. The shortest transitions displayed additional rate-related effects. This last observation may be due to differences in the degree of dispersion of activity in the cochlea when high-rate transitions are effectively treated as non-time-varying, wideband events. The other results may reflect mechanisms that extract the temporal envelopes of signals: Envelope slope and magnitude differences are proposed to provide discriminative cues that supplement or supplant weaker spectrally based pitch/timbre cues for transitions in the short-to-moderate duration range. It is speculated that these cues may also support some speech perceptual decisions.

Attention↗
PubMed1994

Psychoacoustic equivalence of frequency modulation and quasi-frequency modulation.

Frequency modulation (FM) is known to be reasonably approximated by quasi-frequency modulation (QFM) for small modulation indices, beta, but the range of beta for which this approximation is appropriate is unclear. Thresholds for discrimination between FM and QFM with equal beta's are obtained in order to estimate an upper bound on beta for determining when this approximation is valid psychoacoustically, i.e., when FM and QFM are indiscriminable. At low modulation frequencies (fm < or = 4 Hz), QFM is never a valid approximation to FM at any detectable modulation level since discrimination thresholds are below FM detection thresholds. For modulation frequencies between 8 and 32 Hz, discrimination thresholds are approximately -2.5 dB (20 log beta) and can be accounted for by detection of envelope fluctuations in the QFM signal. For modulation frequencies at 64 Hz and above, discrimination thresholds improve with increasing modulation frequency in the same manner as FM and QFM detection thresholds. Discrimination in this frequency region seems to be mediated by detection of the component 2fm Hz below the carrier, i.e., by the most detectable component in the FM signal which does not occur in the QFM signal.

Adult↗
PubMed2002

[Reliability, trainability and stability of auditory discrimination performance in 2 computer-assisted assessment and training methods].

OBJECTIVES: The present study focuses on the possibilities and effects of training dyslexic children in tone and phoneme discrimination tasks. METHODS: A computer program was developed to train dyslexic children to discriminate between tone and speech stimuli. The correlation between auditory discrimination and reading and orthography performance was then tested in a preliminary study of n = 63 children. In a prospective study 44 children were assigned to one of three paralyzed groups: tone training, phoneme training or a control group. Upon completion of the initial diagnostics for all groups, the two training groups received four weeks of discrimination training, after which all three groups were immediately re-tested for the first time. Parallel thereto all children underwent specific training in reading and orthography at their school. Six months later all were re-tested a second time. RESULTS: Both test methods showed a high reliability (rn = .94; .95). Significant correlations between auditory discrimination and reading and orthography performance were confirmed. Auditory discrimination was significantly trainable. Specific training effects, as well as independent developmental effects were found. While the training effects of phoneme discrimination were stable over six months, those of tone discrimination were not. CONCLUSION: The central auditory discrimination between tone and phoneme stimuli can be trained successfully in dyslexic children and might also affect their reading and orthography performance.

Child↗
PubMed1991

Reduction of unique noise in the psychophysics of hearing by Group Operating Characteristic analysis.

Group Operating Characteristic (GOC) analysis can be used to reduce the effects of unique noise on data from psychophysical experiments on hearing. Unique noise can come from physiological sources such as heartbeat and breathing and from other internal sources such as criterion variability, inattention, and faulty memory. The theory of GOC analysis is described and applied to the results of frequency discrimination experiments with human, pigeon, and simulated observers. The method yields relatively unattenuated measures of sensitivity, recovers Receiver Operating Characteristic curves from noisy choice data, and estimates the relative magnitudes of unique and common noise.

Animals↗
PubMed1998

Target flutter rate discrimination by bats using frequency-modulated sonar sounds: behavior and signal processing models.

This study utilized psychophysical data and acoustical measurements of sonar echoes from artificial fluttering targets to develop insights to the information used by FM bats to discriminate the wingbeat rate of flying insects. Fluttering targets were produced by rotating blades that moved towards the bat, and the animal learned to discriminate between two rates of movement, a reference rate (30 or 50 Hz) and a slower, variable rate. Threshold discrimination performance depended on the rotation rate of the reference target, with a difference value of 9 Hz for the reference rate of 30 Hz and 14 Hz for the reference rate of 50 Hz. Control experiments demonstrated that the bats used sonar echoes from the moving targets to perform the discrimination task. Acoustical measurements showed that the moving target produced a Doppler shift in the echo and a concomitant change in the arrival time of each frequency in the linear period FM sweep. The difference in delay between echoes from moving and stationary parts varied linearly with flutter rate and depended on the characteristics of the bat's sonar sounds. Simulations also showed a reduction in average echo bandwidth with increasing flutter rate, which may account for a higher delay discrimination threshold using the 50-Hz reference rate. This work suggests that Doppler-induced changes in echo delays produced by fluttering targets may contribute to the FM bat's perception of flying insect prey.

Acoustics↗
PubMed1993

Modeling perceived relationships between melody, harmony, and key.

Perceptual relationships between four-voice harmonic sequences and single voices were examined in three experiments. In Experiment 1, listeners rated the extent to which single voices were musically consistent with harmonic sequences. When harmonic sequences did not change key, judgments were influenced by three sources of congruency: melody (whether the single voice was the same as the soprano voice of the harmonic sequence), chord progression (whether the single voice could be harmonized to give rise to the chord progression of the harmonic sequence), and key structure (whether or not the single voice implied modulation). When key changes occurred, sensitivity to sources of congruency was reduced. In Experiment 2, another interpretation of the results was examined: that consistency ratings were based on congruency in well-formedness. Listeners provided well-formedness ratings of the single voices and harmonic sequences. A multiple regression analysis suggested that consistency ratings were based not merely on well-formedness but on congruency in melody, chord progression, and key structure. In Experiment 3, listeners rated the extent of modulation in harmonic sequences and in each voice of the sequences. Discrimination between modulation conditions was greater for single voices than for harmonic sequences, suggesting that abstraction of key from melody may occur without reference to implied harmony. A partially hierarchical system for processing melody, harmony, and key is proposed.

Adult↗
PubMed1983

Event-related potentials recorded during the discrimination of improbable stimuli.

In three separate experiments using auditory stimuli, subjects detected improbable targets in an on-going train of standard stimuli. In experiment I there were two equally improbable target stimuli, one difficult to discriminate from the standard stimuli and one easy to discriminate. Experiment II investigated the effects of discrimination difficulty using four different targets, each equal in probability. Experiment III evaluated the effects of both target discriminability and probability on the target-evoked potentials. The subjects in all three experiments consistently displayed delayed reaction times and higher percentages of misses with the more difficult targets. The amplitude of the N1 wave to target stimuli increased as target discriminability was increased. The latencies of the target-evoked N2 and P3 waves increased and the amplitude of the P3 decreased as target discriminability decreased. The amplitude of the N2 wave increased as the target discrimination became more difficult. The amplitude of the N2 wave elicited by an easy target was enhanced by making the target highly improbable whereas probability did not affect the N2 elicited by a difficult target.

Adolescent↗
PubMed1998

Auditory frequency discrimination in the white rat.

Frequency discrimination was investigated in the albino rat using a modified go/no-go positive reinforcement procedure in which subjects reported frequency increments in an ongoing series of pure tone bursts. Weber ratios (frequency difference limen/frequency) were measured from 5 to 32 kHz at 50 dB sound pressure level. A signal detection analysis of the procedure enabled a direct comparison to be made with the rat's performance in a discrete trial go/no-go task. A mean Weber ratio of 3.06+/-0.44% was measured in the frequency range 5-32 kHz. This indicates that the rat has better frequency discrimination acuity than has previously been thought. The result is discussed in the context of factors affecting performance. Among the factors that were explored we found that long training times and the specific training paradigm played important roles. In comparison to discrete trial go/no-go paradigms, rats performed much better when detecting signals from a repeating background. Frequency discrimination performance decreased linearly for tones less than 50 ms in duration. For longer tone duration performance was unaffected. The means and variability of reaction times for threshold changes of frequency were greater in comparison with supra-threshold frequency changes.

Acoustic Stimulation↗
PubMed1987

Individual differences in auditory capabilities. I.

Twenty-eight audiometrically normal adult listeners were given a variety of auditory tests, ranging from quiet and masked thresholds through the discrimination of simple and moderately complex temporal patterns. Test-retest reliability was good. Individual differences persisted on a variety of psychoacoustic tasks following a period of training using adaptive threshold-tracking methods, and with trial-by-trial feedback. Large individual differences in performance on temporal-sequence-discrimination tasks suggest that this form of temporal processing may be of clinical significance. In addition, high correlations were obtained within given classes of tests (as, between all tests of frequency discrimination) and between certain classes of tests (as, between tests of frequency discrimination and those of sequence discrimination). Patterns of individual differences were found which support the conclusion that individual differences in auditory performance are, in part, a function of patterns of independent abilities.

Adolescent↗
PubMed1990

Discrimination of modulation depth of sinusoidal amplitude modulation (SAM) noise.

The detection of sinusoidal amplitude modulation (SAM) provides a lower bound on the degree to which temporal information in the envelope of complex waveforms is encoded by the auditory system. The extent to which changes in the amount of modulation are discriminable provides additional information on the ability of the auditory system to utilize envelope fluctuations. Results from an experiment on the discrimination of modulation depth of broadband noise are presented. Discrimination thresholds, expressed as differences in modulation power, increase monotonically with the modulation depth of the standard, but do not obey Weber's law. The effects of carrier level and of modulation frequency are consistent with those observed in modulation detection: Changes in carrier level have little effect on modulation discrimination; changes in modulation frequency also have little effect except for standards near the modulation detection threshold. The discrimination of modulation depth is consistent with the leaky-integrator model of modulation detection for standards below--10 dB (20 log ms); for standards greater than--10 dB, the leaky integrator predicts better performance than that observed behaviorally.

Attention↗
PubMed1984

Factors influencing the masking level difference in cochlear hearing-impaired and normal-hearing listeners.

The masking level difference (MLD) at 500 Hz was examined in wide-band (960 Hz) and narrow-band (50 Hz) noise for normal-hearing subjects and subjects with symmetrical mild-to-moderate cochlear hearing loss. Monaural tasks of intensity discrimination, temporal resolution, and frequency resolution were performed in order to examine relationships between monaural dysfunction and MLD performance. Interaural time discrimination for a 500-Hz pure tone also was examined. The performance of the hearing-impaired subjects was poorer than that of the normal-hearing subjects for MLD, interaural delta t, and most monaural tasks. However, no significant relationships were found between monaural and MLD performance when effects of threshold were taken into account. MLDs were more reduced in wide-band noise than in narrow-band noise for the hearing-impaired subjects (when contrasted with normal-hearing subjects). MLD performance was correlated with interaural time discrimination, and it is suggested that one reason for poor MLD performance with hearing impairment may be poor temporal coding of stimulus-fine structure.

Adult↗
PubMed2001

Exploring the functional neuroanatomy of music performance, perception, and comprehension.

This chapter highlights findings by my colleagues and me in four neuroimaging and neurological studies of music performance, perception, and comprehension. These investigations elucidate the neural subsystems supporting musical pitch, melody, harmony, rhythm, tempo, meter, and duration. In a positron emission tomography (PET) study of pianists, a memorized performance of a musical piece was contrasted with that of scales to localize brain areas specifically supporting music. A second PET study assayed brain areas subserving selectively the comprehension of harmony, melody, and rhythm. Musicians sight-read a score while detecting specific melodic, harmonic, or rhythmic errors in its heard performance. In a third PET study, musicians and nonmusicians discriminated pairs of rhythms with respect to pattern, tempo, meter, or duration. Data in these studies implicated the cerebellum in nonmotor, nonsomatic, sensory, or cognitive processing. In a fourth study, neurological patients with degeneration of the cerebellum were found to be impaired in fine discrimination of pitch. Overall, these data suggest that the neural systems underlying music are distributed throughout the left and right cerebral and cerebellar hemispheres, with different aspects of music processed by distinct neural circuits. Also discussed are key issues for interpreting the role in music of brain areas implicated in neuroimaging studies.

Auditory Perception↗
PubMed1997

Auditory profile analysis: is there perceptual constancy for spectral shape for stimuli roved in frequency?

The ability to discriminate between two spectral shapes was investigated using a one-interval, two-alternative forced choice procedure. Each stimulus consisted of seven components equally spaced on a logarithmic frequency scale (frequency ratio of 1.2 between adjacent components). The two spectral shapes were produced by first generating a complex each of whose components was equally loud (when heard in isolation) and then increasing the level of either the third or the fifth component by a certain amount. To render pitch an unusable cue, the center frequencies of the stimuli were randomly varied between presentations (maintaining the ratio between adjacent components) over a range of about three octaves (279-2074 Hz). The data indicate that listeners were not able to distinguish between the two types of profiles even for very large increments in level of the third and the fifth components. The results suggest that there is no perceptual constancy for this type of spectral shape for stimuli roved over a sufficiently large frequency range. The spectral shape cannot be perceived independently of stimulus frequency. The results are related to the multi-channel model applied in profile analysis tasks.

Adult↗
PubMed1990

Identification and discrimination disorders in auditory perception: a report on two cases.

Auditory perception was investigated in two brain-damaged subjects. The first patient had a left temporoparietal ischaemic lesion. He presented a right-ear extinction in dichotic tasks, as well as difficulties in understanding and repeating verbal material and impaired identification of melodies. All discrimination tests were well performed. The second patient had a right capsulolenticular and frontal ischaemic lesion. He presented a left ear dichotic extinction and severe difficulties in discrimination of environmental sounds and melodies but no major difficulty in naming and identification. From these results, it is hypothesized that identification and discrimination involve distinct mechanisms within the processing of auditory stimuli, and that they may be selectively disrupted in brain-damaged subjects.

Adult↗
PubMed1998

Increased auditory cortical representation in musicians.

Acoustic stimuli are processed throughout the auditory projection pathway, including the neocortex, by neurons that are aggregated into 'tonotopic' maps according to their specific frequency tunings. Research on animals has shown that tonotopic representations are not statically fixed in the adult organism but can reorganize after damage to the cochlea or after training the intact subject to discriminate between auditory stimuli. Here we used functional magnetic source imaging (single dipole model) to measure cortical representations in highly skilled musicians. Dipole moments for piano tones, but not for pure tones of similar fundamental frequency (matched in loudness), were found to be enlarged by about 25% in musicians compared with control subjects who had never played an instrument. Enlargement was correlated with the age at which musicians began to practise and did not differ between musicians with absolute or relative pitch. These results, when interpreted with evidence for modified somatosensory representations of the fingering digits in skilled violinists, suggest that use-dependent functional reorganization extends across the sensory cortices to reflect the pattern of sensory input processed by the subject during development of musical skill.

Adult↗