Frequency Difference Limens Research Articles

Frequency and intensity discrimination in children with cochlear implants

BackgroundFrequency discrimination underlies more complicated auditory activities like speech comprehension and interpretation. However, intensity differences indicate how far apart noises are. This study aimed to evaluate and compare results of frequency modulation and difference limen for intensity in children with cochlear Implants (CI) as well as normal hearing children.ResultsThis case–control work was performed on 40 children, aged from 5–18 years, divided into two equal groups: a study group with unilateral CI and a control group with normal peripheral hearing. All patients were subjected to otological examination, audiological evaluation, frequency modulation difference limen (FMDL) and difference limen for intensity (DLI) tests. Patients with CI, as compared to normal hearing (NH) subjects, required significantly higher frequencies to discriminate FMDL and DLI respectively (P value = 0.001). At 2000 and 4000 Hz: FMDL had a significant diagnostic power for patients with CI (AUC = 0.980, 0.998 respectively, P < 0.001), at cut off 1.5, with 100% sensitivity and 100% specificity. While, at 4000 Hz: DLI had a significant diagnostic power for patients with CI (AUC = 0.999, P < 0.001), at cut off 1.5, with 100% sensitivity and 100% specificity.ConclusionA statistically substantial variation was observed among CI and NH children in FMDL and DLI at all frequencies tested. Patients with CI required significantly higher frequencies to discriminate as compared to NH subjects. Frequencies at 2000 Hz and 4000 Hz possess the best specificity and sensitivity of FMDL. While frequency 4000 Hz possess the best specificity and sensitivity of DLI.

Frequency-discrimination and speech-perception characteristics of bone-conducted sound presented to the facial parts

Bone-conducted (BC) sound is typically presented to the mastoid process of the temporal bone or the condyle process of the mandible. However, a method of presenting BC sound to facial parts such as the nose and cheek have also been investigated recently. Since the face is one of the most complex structures in the human body, slight differences in the presentation parts of the vibrator will also change the perception and propagation mechanism. However, the characteristics of BC sound presented to the face have not yet been studied in detail. We have previously discussed the differences in perception (hearing thresholds) and propagation characteristics among facial parts. Here, to test the frequency-discrimination ability, we measured difference limens for frequency. We also conducted monosyllable articulation tests in Japanese to assess the speech-perception characteristics when BC sounds are presented to various facial (nasal, infraorbital region, zygomatic, jaw angle, and chin) and conventional (mastoid and condyle process) parts. The results obtained showed that the frequency resolution and intelligibility of the facial parts were about the same as those of the conventional parts. It is indicated that practical frequency information and speech perception are possible with BC devices attached to certain facial parts.

The Role of Entrainment and Aperiodicity in Vibrotactile Discrimination

The extent to which entrainment – the phenomenon in neuroscience where neurons synchronize their firing patterns to external stimuli with rhythmic or periodic features – occurs in response to aperiodic or irregular flutter stimuli remains debatable. It has been proposed by Mountcastle et al. that information is processed in a periodic manner; however, more recently, Romo et al. challenged Mountcastle’s theory and proposed that flutter stimulus was encoded based on the rapidly adapting fibers, not the periodicity.1-5 Therefore, if Mountcastle et al. is correct, the brain should be more adept at discriminating frequency between periodic stimuli than between aperiodic stimuli; conversely, if Romo et al. is correct, the brain should be equally good at discriminating frequencies between periodic and aperiodic stimuli. In this study, a two-point vibrotactile stimulation device (The Brain Gauge, Cortical Metrics, USA) was used to stimulate digits II and III of 43 participants’ preferred hand to determine their difference limen (DL) for both amplitude (AD) and frequency (FD) discrimination tests, given aperiodic or periodic stimuli. The tests were performed in the following order: periodic AD, aperiodic AD, periodic FD, and aperiodic FD. The results suggest that the periodicity of the stimuli affects frequency discrimination more than amplitude discrimination and the participants were significantly better at discriminating stimuli with periodic frequencies than aperiodic frequencies. A paired, one-tailed t-test indicated that the subject DLs resulting from periodic stimuli were significantly different (p&lt;0.05) from that resulting from aperiodic stimuli for frequency discrimination, while it was not statistically significant for amplitude discrimination. The results were in favor of Mountcastle’s theory; however, more trials with a more controlled experimental environment may be needed to definitively conclude.

Effect of diotic versus dichotic presentation on the pitch perception of tone complexes at medium and very high frequencies

Difference limens for fundamental frequency (F0), F0DLs, are usually small for complex tones containing low harmonics that are resolved in the auditory periphery, but worsen when the rank of the lowest harmonic increases above about 6–8 and harmonics become less resolved. The traditional explanation for this, in terms of resolvability, has been challenged and an alternative explanation in terms of harmonic rank was suggested. Here, to disentangle the effects of resolvability and harmonic rank the complex tones were presented either diotically (all harmonics to both ears) or dichotically (even and odd harmonics to opposite ears); the latter increases resolvability but does not affect harmonic rank. F0DLs were measured for 14 listeners for complex tones containing harmonics 6–10 with F0s of 280 and 1400 Hz, presented diotically or dichotically. For the low F0, F0DLs were significantly lower for the dichotic than for the diotic condition. This is consistent with a benefit of increased resolvability of harmonics for F0 discrimination and extends previous results to harmonics as low as the sixth. In contrast, for the high F0, F0DLs were similar for the two presentation modes, adding to evidence for differences in pitch perception between tones with low-to-medium and very-high frequency content.

Characteristics of Frequency Resolution and Speech Perception Using Bone Conduction on Different Human Facial Parts.

In conventional bone-conduction (BC) devices, a vibrator is typically attached to the mastoid process of the temporal bone or the condyle process of the mandible. However, BC-sound presentations to facial parts such as the nose and cheek have also been investigated recently. As the face is the among the most complex structures of the human body, transmission of sounds using BC on different facial parts are likely to show different perception and propagation characteristics than those presented to conventional parts. However, the characteristics of BC sound presented to different part of the face have not yet been studied in detail. To test the frequency discrimination ability, we measured difference limens for frequency (DLFs). We also conducted monosyllable articulation tests in Japanese to assess the speech-perception characteristics when BC sounds are presented to various facial (nasal, infraorbital region, zygomatic, jaw angle, and chin) and conventional (mastoid and condyle process) parts of a normal-hearing subject. The results suggest that, at least in the parts investigated in the current study, the frequency resolution and intelligibility of the facial parts were about the same as those of the conventional parts. These results indicate that practical frequency information and speech perception are possible with BC devices attached to different facial parts.

A Bayesian inverse approach to identify and quantify organisms from fisheries acoustic data

Abstract Identifying sound-scattering organisms is a perennial challenge in fisheries acoustics. Most practitioners classify backscatter based on direct sampling, frequency-difference thresholds, and expert judgement, then echo-integrate at a single frequency. However, this approach struggles with species mixtures, and discards multi-frequency information when integrating. Inversion methods do not have these limitations, but are not widely used because species identifications are often ambiguous and the algorithms are complicated to implement. We address these shortcomings using a probabilistic, Bayesian inversion method. Like other inversion methods, it handles species mixtures, uses all available frequencies, and extends naturally to broadband signals. Unlike previous approaches, it leverages Bayesian priors to rigorously incorporate information from direct sampling and biological knowledge, constraining the inversion and reducing ambiguity in species identification. Because it is probabilistic, a well-specified model should not produce solutions that are both wrong and confident. The model is based on physical scattering processes, so its output is fully interpretable, unlike some machine learning methods. Finally, the approach can be implemented using existing Bayesian libraries and is easily parallelized for large datasets. We present examples using simulations and field data from the Gulf of Alaska, and discuss possible applications and extensions of the method.

Deep band modulation, frequency discrimination, temporal resolution and audibility effects: phrase perception with and without hearing impairment among older adults

Objective The temporal envelope enhancement using deep band modulation (DBM) exaggerates the temporal peaks and valleys in the speech signal, thereby reducing the difficulty in the perception of speech in noise. Method Ten participants in each group of older adults with and without hearing loss in 65 to 83 years were recruited. A repeated measures research design was utilised to investigate phrase perception in unprocessed and deep band modulated phrases at different signal-to-noise (SNR) ratios (−4, 0, and +4). Temporal processing, spectral discrimination and speech intelligibility index were assessed. Results Regardless of the group, the phrase perception in the deep band modulated condition was significantly better than the unprocessed condition at each SNR. A significantly strong negative correlation was observed between: Gap detection threshold (GDT) and phrase perception scores in unprocessed condition at −4 dB SNR in each group; frequency difference limen in each condition and DBM phrase perception at −4 dB SNR in the older adult group with hearing impaired (OAG-HI) group. Furthermore, audibility reflected in the speech intelligibility index (SII) did not influence phrase recognition irrespective of condition, SNRs and group. Conclusion Increased modulation depth enables the participants to use the available temporal envelope, especially at the portion of the phrase where noise is less energetically masked.

Threshold and frequency- and temporal resolutions of distantly presented bone-conducted sound in the audible-frequency range

As a vibrator needs to be pressed onto the osseous parts of the head, bone conduction is often accompanied by pain and esthetic problems. To solve these problems, a “distant presentation” that involves presenting vibrators to the neck, trunk, or upper limb was proposed. Our previous studies focused on the perceptual and propagation characteristics of distantly presented bone-conducted sounds in the ultrasonic range. However, only a few studies have been conducted in the audible-frequency range. In this study, to examine the basic properties of distantly presented bone-conduction perception in the audible-frequency range, hearing thresholds, difference limens for frequency, and temporal modulation transfer functions were measured with insulated air-conducted sounds. The results indicate that the distance attenuation is much larger than that in the ultrasonic range, and the degradation of frequency and temporal information occurring in the propagation process of bone-conducted sounds is sufficiently small for the transmission of sound information.

WSTĘPNE BADANIE PSYCHOAKUSTYCZNE ZASTOSOWANIA PROCEDURY SIAM DO POMIARU PROGÓW RÓŻNICOWANIA CZĘSTOTLIWOŚCI

BackgroundThe study investigated the cause of varying estimates of frequency difference limens (DLs) in delayed comparison tasks involving pitch retention in auditory working memory (AWM). Using procedures adapted from the method of constant stimuli (MCS) and the single-interval adjustment matrix (SIAM), we sought to determine via 3 experiments whether the disparity in frequency DLs obtained using each procedure was due to the method of measurement (Experiment 1), the response format (Experiment 2), or performance feedback (Experiment 3).Material and methodsFive adults (ages 21 to 38 years) with hearing within normal limits participated in Experiments 1 and 2, and seven adults (ages 20 to 30 years) with hearing within normal limits participated in Experiment 3. Delayed comparison tasks were used to evaluate frequency DLs under SIAM and MCS.ResultsOur preliminary results suggest that DL values for pitch discrimination are more influenced by response format than by the measurement procedure or performance feedback. Regardless of the method used, DL values were greater in the condition containing intervening stimuli compared to the condition lacking intervening stimuli.ConclusionsPreliminary findings suggest there is consistency in the listener’s adopted criterion (i.e., judgment rationale) across the psychoacoustic methods investigated. Performance measures suggest that SIAM is as accurate as MCS, but it is noteworthy that two SIAM measurement runs using the "same/different" response format is more efficient than four runs with MCS. Future application of the SIAM procedure for measuring DL values might, with larger sample sizes, identify additional factors that contribute to performance and the listener’s adopted criterion, since data collection time is appreciably shorter with SIAM.

Diotic and Dichotic Mechanisms of Discrimination Threshold in Musicians and Non-Musicians.

The perception of harmonic complexes provides important information for musical and vocal communication. Numerous studies have shown that musical training and expertise are associated with better processing of harmonic complexes, however, it is unclear whether the perceptual improvement associated with musical training is universal to different pitch models. The current study addresses this issue by measuring discrimination thresholds of musicians (n = 20) and non-musicians (n = 18) to diotic (same sound to both ears) and dichotic (different sounds to each ear) sounds of four stimulus types: (1) pure sinusoidal tones, PT; (2) four-harmonic complex tones, CT; (3) iterated rippled noise, IRN; and (4) interaurally correlated broadband noise, called the “Huggins” or “dichotic” pitch, DP. Frequency difference limens (DLF) for each stimulus type were obtained via a three-alternative-forced-choice adaptive task requiring selection of the interval with the highest pitch, yielding the smallest perceptible fundamental frequency (F0) distance (in Hz) between two sounds. Music skill was measured by an online test of musical pitch, melody and timing maintained by the International Laboratory for Brain Music and Sound Research. Musicianship, length of music experience and self-evaluation of musical skill were assessed by questionnaire. Results showed musicians had smaller DLFs in all four conditions with the largest group difference in the dichotic condition. DLF thresholds were related to both subjective and objective musical ability. In addition, subjective self-report of musical ability was shown to be a significant variable in group classification. Taken together, the results suggest that music-related plasticity benefits multiple mechanisms of pitch encoding and that self-evaluation of musicality can be reliably associated with objective measures of perception.

Basic properties of distantly-presented bone-conduction perception.

Since a vibrator needs to be pressed onto the osseous parts of the head, bone-conduction (BC) is often accompanied by pain and esthetic problems. In order to solve these problems, "distant presentation" has been proposed. In the distant presentation, vibrators are presented to the neck, upper limb or trunk. Our previous studies focused on the perception and propagation characteristics of distantly-presented BC sound in the ultrasonic range and an application to a novel audio-interface. On the other hand, a limited number of studies have been conducted on distantly-presented BC in the audible-frequency range. In this study, to examine the basic properties of the distantly-presented BC perception in the audible-frequency range, hearing thresholds, difference limens for frequency (DLFs) and temporal modulation transfer functions (TMTFs) were measured under the condition that AC sounds were insulated sufficiently. The results obtained indicated that BC sounds can be clearly perceived at distal parts of the body even in the audible-frequency range and no significant degradation of frequency and temporal information occurs in the propagation process in the body.

Scalable, probabilistic echo inversion for multifrequency and broadband acoustic surveys

Identifying biological scatterers is a perennial challenge in fisheries acoustics. Most practitioners classify backscatter based on direct sampling and frequency-difference thresholds, then integrate at a single frequency. However, this approach struggles with species mixtures, and discards multi-frequency information when integrating. Inversion methods do not have these limitations, but are seldom used, because their species identifications are often ambiguous and their algorithms complicated to implement. We address these shortcomings with a probabilistic, Bayesian inversion method. Like other inversion methods, it handles species mixtures, uses all available frequencies, and extends naturally to broadband signals. Unlike prior approaches, it leverages Bayesian priors to rigorously incorporate information from direct sampling and biological knowledge, constraining the inversion and reducing ambiguity in species identification. Because it is probabilistic, it can be trusted to run automatically: it should not produce solutions that are both wrong and confident. Unlike some data-driven machine learning models, it is based on acoustical scattering processes, so its inferences are physically interpretable. Finally, the approach is straightforward to implement using existing Bayesian libraries, and is easily parallelized for large datasets. We present examples using simulations and field data from the Gulf of Alaska, and discuss possible extensions and applications of the method.

Effect of Efferent Stimulation on the Differential Sensitivity in Individuals with Normal Hearing.

The aim of the article was to compare the conditions of silent and contralateral noise on Differential sensitivity in normal hearing individuals. A total of 40 participants (20 males and 20 females) were enrolled in the study with a mean age of 21.7years, participants with normal hearing thresholds and no history of middle ear pathology were enrolled for the study. Difference limen tests such as difference limen for intensity (DLI), difference limen for frequency (DLF), and difference limen for time (DLT) were carried out in these 40 individuals in the two conditions of silent and contralateral noise using MATLAB. Statistical analysis was carried out using the SPSS version 25.0 were descriptive and inferential statistics were carried out. Data was normally distributed on the Shapiro-Wilk's test of normality due to which a paired t test was carried out to establish the nature of significance between the silent and contralateral noise condition. Results reveal the presence of significant difference (P < 0.01) between the groups for DLF and DLT with contralateral noise condition performing better than silent condition for the parameters. However, no significant difference was obtained for DLI. There is a positive effect of the efferent auditory pathway on the Differential sensitivity thus implying that speech perception in noise is improved in the presence of background noise for normal hearing individuals due to this effect. But in case of DLI, the reduced spread of excitation could be the reason why there were no significant differences between silent and contralateral noise condition.

Effect of Musical Experience on Cochlear Frequency Resolution: An Estimation of PTCs, DLF and SOAEs.

Background: There is a lot of debate on whether musical experience/training can affect cochlear filter characteristics and thereby enhance frequency resolution skills in musicians (Ms). Thus, the objective of the study was to compare between Ms and non-musicians (NMs) and correlate the frequency resolution skills with years of musical experience, the difference limen for frequency (DLF), and the Q10 values of psychophysical tuning curves (PTCs) measured at 2 characteristic frequencies (CFs), 1000 and 4000 Hz. The secondary objective was to find out whether spontaneous otoacoustic emissions (SOAEs) can be recorded among Ms more frequently than among NMs. Methods:Thirty-six listeners with normal hearing participated in the study. They were 18 Ms with a minimum of 8 years of musical experience, and 18 NMs. Forward-masked PTCs and DLF tests were assessed for each listener in the right ear at 2 CFs, 1 and 4 kHz, and SOAEs were measured using standard protocol. Results:The results obtained indicated that values of the psychophysical measures, DLF and Q10, were better among the Ms group. Statistically significant differences were seen when measurements were done at 1 KHz and 4 KHz. SOAEs were recorded in a higher number of Ms than NMs. Musical experience had a moderate positive correlation with PTC Q10 values at both 1 and 4 kHz, but not DLF values. Conclusion:This study indicates that musical experience enhances peripheral filtering, and thereby betters cochlear frequency selectivity in Ms.

Low-sound-level auditory processing in noise-exposed adults

Early signs of noise-induced hearing damage are difficult to identify, as they are often confounded by factors such as age, audiometric thresholds, or even music experience. Much previous research has focused on deficits observed at high intensity levels. In contrast, the present study was designed to test the hypothesis that noise exposure causes a degradation in low-sound-level auditory processing in humans, as a consequence of dysfunction of the inner hair cell pathway. Frequency difference limens (FDLs) and amplitude modulation depth discrimination (MDD) were measured for five center frequencies (0.75, 1, 3, 4 and 6 kHz) at 15 and 25 dB sensation level (SL), as a function of noise exposure, age, audiometric hearing loss, and music experience. Forty participants, aged 33-75 years, with normal hearing up to 1 kHz and mild-to-moderate hearing loss above 2 kHz, were tested. Participants had varying degrees of self-reported noise exposure, and varied in music experience. FDL worsened as a function of age. Participants with music experience outperformed the non-experienced in both the FDL and MDD tasks. MDD thresholds were significantly better for high-noise-exposed, than for low-noise-exposed, participants at 25 dB SL, particularly at 6 kHz. No effects of age or hearing loss were observed in the MDD. It is possible that the association between MDD thresholds and noise exposure was not causal, but instead was mediated by other factors that were not measured in the study. The association is consistent, qualitatively, with a hypothesized loss of compression due to outer hair cell dysfunction.

Evaluation of difference limen for frequency, intensity and duration in individuals with visual impairment

Introduction Individuals with visual impairment are known to have better auditory abilities than individuals with normal vision. There is a literature shortage that has attempted to assess differential sensitivity for frequency, intensity, and duration in individuals with visual impairment. Objective Thus, the study attempted to determine differences in difference limen for frequency, intensity, and duration between individuals with visual impairment and individuals with normal vision. Methods 30 individuals with normal vision and 30 individuals with visual impairment (15 males and 15 females in each) participated in the study, and their DLI, DLF, DLT were assessed using the mlp toolbox. Results The study results showed that the differential sensitivity was superior for individuals with visual impairment compared to sighted people. Conclusions The results agree with previous studies, suggesting a superior auditory performance in individuals with visual impairment. Further studies on a larger group of population are essential for better generalisation of the results.

Unilateral auditory deprivation in humans: Effects on frequency discrimination and auditory memory span in the normal ear

Hearing with one ear is associated with auditory deprivation leading to cortical neuronal reorganization. Despite evidence for substantial effects of unilateral input on cortical and sub-cortical structures, the functional consequences of such alterations on human hearing is underexplored. Unilateral hearing impairment offers a unique model to study the perceptual consequences of cortical reorganization. The present study provides evidence for larger (poorer) difference limens for frequency for sounds heard by the normal ear of listeners with unilateral hearing loss relative to bilaterally normal-hearing controls. This difference in frequency discrimination ability was observed for the low (250 Hz), but not for the high-frequency tone (4000 Hz). Besides auditory perceptual effects, we also found reduced working memory capacity as revealed by forward and backward digit span measures. Contrary to the expectation, there was no significant association between frequency discrimination and working memory capacity in listeners with unilateral hearing loss. Auditory deprivation associated with unilateral hearing impairment affects low-frequency (pitch) discrimination and working memory capacity despite normal hearing in the intact ear. Such deficits in basic auditory processes and memory span for sounds heard by the normal ear may contribute to the hearing and communication difficulties experienced by listeners with unilateral or single-sided deafness.

Comparisons in Frequency Difference Limens Between Sequential and Simultaneous Listening Conditions in Normal-Hearing Listeners.

Purpose We compared frequency difference limens (FDLs) in normal-hearing listeners under two listening conditions: sequential and simultaneous. Method Eighteen adult listeners participated in three experiments. FDL was measured using a method of limits for comparison frequency. In the sequential listening condition, the tones were presented with a half-second time interval in between, but for the simultaneous listening condition, the tones were presented simultaneously. For the first experiment, one of four reference tones (125, 250, 500, or 750 Hz), which was presented to the left ear, was paired with one of four starting comparison tones (250, 500, 750, or 1000 Hz), which was presented to the right ear. The second and third experiments had the same testing conditions as the first experiment except with two- and three-tone complexes, comparison tones. The subjects were asked if the tones sounded the same or different. When a subject chose "different," the comparison frequency decreased by 10% of the frequency difference between the reference and comparison tones. FDLs were determined when the subjects chose "same" 3 times in a row. Results FDLs were significantly broader (worse) with simultaneous listening than with sequential listening for the two- and three-tone complex conditions but not for the single-tone condition. The FDLs were narrowest (best) with the three-tone complex under both listening conditions. FDLs broadened as the testing frequencies increased for the single tone and the two-tone complex. The FDLs were not broadened at frequencies > 250 Hz for the three-tone complex. Conclusion The results suggest that sequential and simultaneous frequency discriminations are mediated by different processes at different stages in the auditory pathway for complex tones, but not for pure tones.

The Contribution of Frequency Discrimination Ability to Auditory Temporal Patterning Tests in Children.

Purpose The Pitch Patterns Test (PPT) and the Duration Patterns Test (DPT) are clinical auditory processing tests that evaluate temporal patterning skills based on pitch (PPT) or duration (DPT) aspects of sound. Although temporal patterning tests are categorized under the temporal processing domain, successful performance on the PPT also relies on accurate pitch discrimination. However, the relationship between pitch discrimination ability and temporal patterning skills has not been thoroughly evaluated. This study examined the contribution of pitch discrimination ability to performance on temporal patterning in children through the use of a pitch discrimination task and the PPT. The DPT was also given as a control measure to assess temporal patterning with no pitch component. Method Thirty-two typically developing elementary school-age children (6;11-11;3 [years;months]) with normal hearing were given a series of three counterbalanced tasks: an adaptive psychophysical pitch discrimination task (difference limen for frequency [DLF]), the PPT, and the DPT. Results Correlational analysis revealed moderate correlations between DLF and PPT scores. After accounting for age, results of a linear regression analysis suggested that pitch discrimination accounts for a significant amount of variance in performance on the PPT. No significant correlation was found between DLF and DPT scores, supporting the hypothesis that the pitch task had no significant temporal patterning component contributing to the overall score. Discussion These findings indicate that pitch discrimination contributes significantly to performance on the PPT, but not the DPT, in a typically developing pediatric population. This is an important clinical consideration in both assessment and utilization of targeted therapy techniques for different clinical populations.

Practice Makes Transfer Imperfect: Evidence From Auditory Learning.

Evidence from motor and visual studies suggests that the ability to generalize learning gains to untrained conditions decreases as the training progresses. This decrease in generalization was suggested to reflect a shift from higher to lower levels of neuronal representations of the task following prolonged training. In the auditory modality, however, the few studies that tested the influence of prolonging training on generalization ability showed no decrease and sometimes even an increase in generalization. To test the impact of extending training in a basic psychoacoustic task on the ability to generalize the gains attained in training to untrained conditions. Eighty-two young adults participated in two experiments that differed in the specific training regimen. In both experiments, training was conducted using a difference limen for frequency (DLF) task with an adaptive forced-choice procedure, for either a single- or nine-session training. Following training, generalization to the untrained ear and to an untrained frequency was assessed. (a) Training induced significant learning (i.e., smaller DLF thresholds) following a single session of training, and more so following nine training sessions; (b) results from the combined data from both experiments showed that the ability to generalize the learning gains to the untrained ear and frequency was limited after the extended DLF training; (c) larger improvements under the trained condition resulted in smaller generalization to the untrained conditions. The findings of increased specificity with training in the auditory modality support the notion that gradual changes, both quantitative and qualitative, occur in the neural representations of an auditory task during its acquisition. These findings suggest common underlying mechanisms in basic skill learning across different modalities.