Psychoacoustic Measures Research Articles

Mismatch negativity (MMN) objectively reflects timbre discrimination thresholds in normal-hearing listeners and cochlear implant users

Timbre perception is poor in cochlear implant (CI) users. Most behavioral studies assess timbre discrimination with real instrumental sounds differing in more than one timbre dimension. This study focuses on objective measures of individual discrimination of single timbre dimensions. A psychoacoustic and electrophysiological case-control study of timbre discrimination was conducted in 15 CI users and 15 normal-hearing (NH) listeners. Just noticeable differences (JNDs) for temporal envelope (TE) modulation differences and spectral distribution (S) differences of complex tones were measured in an adaptive three-alternatives forced-choice procedure. From individual JNDs, individual four tone pairs were computed: temporal envelope modulation/spectral distribution timbre discrimination, and above/below JND. With these tone pairs, four randomly arranged oddball paradigms were presented to derive mismatch negativity (MMN), which reflects the ability to automatically detect acoustic changes. JNDs could be derived for all NH listeners. Discrimination of spectral distribution differences and particularly temporal envelope modulation differences were more difficult for CI users. MMN was present in all NH listeners and CI users when the timbre difference was above the individual JND, but not when below JND. Thus, the timbre difference between ‘deviant’ and ‘standard’ tones reflected the individual threshold for automatic detection of timbre changes. We conclude that the timbre perception skills of NH listeners and CI users in particular can be assessed timbre dimension specifically with psychoacoustic measurements and MMN recordings. MMN occurrence reflects the individual JND for temporal envelope modulation and spectral distribution differences and can be used as a clinical tool to monitor auditory-verbal therapy after CI surgery.

Modeling sound-source localization in sagittal planes for human listeners.

Monaural spectral features are important for human sound-source localization in sagittal planes, including front-back discrimination and elevation perception. These directional features result from the acoustic filtering of incoming sounds by the listener's morphology and are described by listener-specific head-related transfer functions (HRTFs). This article proposes a probabilistic, functional model of sagittal-plane localization that is based on human listeners' HRTFs. The model approximates spectral auditory processing, accounts for acoustic and non-acoustic listener specificity, allows for predictions beyond the median plane, and directly predicts psychoacoustic measures of localization performance. The predictive power of the listener-specific modeling approach was verified under various experimental conditions: The model predicted effects on localization performance of band limitation, spectral warping, non-individualized HRTFs, spectral resolution, spectral ripples, and high-frequency attenuation in speech. The functionalities of vital model components were evaluated and discussed in detail. Positive spectral gradient extraction, sensorimotor mapping, and binaural weighting of monaural spatial information were addressed in particular. Potential applications of the model include predictions of psychophysical effects, for instance, in the context of virtual acoustics or hearing assistive devices.

The Influence of Sound Generator Associated With Conventional Amplification for Tinnitus Control: Randomized Blind Clinical Trial

Hearing aids with an integrated sound generator have been used to enhance the treatment of tinnitus. The main aim of this study was to verify whether the combined use of amplification and sound generator is more effective than conventional amplification alone in reducing tinnitus annoyance by means of the use of a new hearing aid with an integrated sound generator. A total of 49 patients underwent a blind randomized clinical trial. Tinnitus annoyance was measured by Tinnitus Handicap Inventory and numerical scales, and psychoacoustic measures of tinnitus were also performed. The sound generator was set at the lowest intensity capable of providing relief from tinnitus. Results showed that 62.5% of the patients presented a reduction in tinnitus annoyance in the combined fitting group and in the group with amplification alone, 78% showed a reduction. This difference between the groups was not statistically significant.

Short-term learning effect in different psychoacoustic measures.

Learning effect has been studied in the literature, but the learning done in short-term training has not been studied. Also, to date, the learning effect of different psychoacoustic measures has not been compared. In the current study, we compared the perceptual learning effect caused by performing four different auditory temporal processing (ATP) tasks in a short-term training design including two training sessions. A total of 74 young, normal-hearing participants each performed one of the following tasks: spectral temporal order judgment (TOJ), dichotic TOJ, gap detection, or duration discrimination. Each task was performed in two consecutive sessions. A learning effect was observed only for the spectral TOJ task. The change from the first to the second session was larger in spectral TOJ (81%) than in dichotic TOJ (2%), gap detection (7%), and duration discrimination (5%). The difference in perceptual learning between spectral TOJ and other ATP tasks suggests that the performance of this task involves other cue(s) in addition to the temporal one.

Calculation of selective filters of a device for primary analysis of speech signals

The amplitude-frequency responses of filters for primary analysis of speech signals, which have a low quality factor and a high rolloff factor in the high-frequency range, are calculated using the linear theory of speech production and psychoacoustic measurement data. The frequency resolution of the filter system for a sinusoidal signal is 40–200 Hz. The modulation-frequency resolution of amplitude- and frequency-modulated signals is 3–6 Hz. The aforementioned features of the calculated filters are close to the amplitudefrequency responses of biological auditory systems at the level of the eighth nerve.

Speech is not special… again.

THE “SPECIALNESS” OF SPEECH As is apparent from reading the first line of nearly any research or review article on speech, the task of perceiving speech sounds is complex and the ease with which humans acquire, produce and perceive these sounds is remarkable. Despite the growing appreciation for the complexity of the perception of music, speech perception remains the most amazing and poorly understood auditory (and, if we may be so bold, perceptual) accomplishments of humans. Over the years, there has been considerable debate on whether this achievement is the result of general perceptual/cognitive mechanisms or “special” processes dedicated to the mapping of speech acoustics to linguistic representations (for reviews see Trout, 2001; Diehl et al., 2004). The most familiar proposal of the “specialness” of speech perception is the various incarnations of the Motor Theory of speech proposed by Liberman et al. (1967; Liberman and Mattingly, 1985, 1989). Given the status of research into audition in the 1950s and 1960s, it is not surprising that speech appeared to require processing not available in “normal” hearing. Much of the work at the time used relatively simple tones and noises to get at the basic psychoacoustics underlying the perception of pitch and loudness (though some researchers like Harvey Fletcher were also working on some basics of speech perception, Fletcher and Galt, 1950; Allen, 1996). Liberman and his collaborators discovered that the discrimination of acoustic changes in speech sounds did not look like the psychoacoustic measures of discrimination for pitch and loudness. Instead of following a Weber or Fechner law, the discrimination function had a peak near the categorization boundary between contrasting phonemes—a pattern of perceptual results that is referred to as Categorical Perception (Liberman et al., 1957). In addition, the acoustic cues to phonemic identity were not readily apparent with similar spectral patterns resulting in different phonemic percepts and acoustically disparate patterns resulting in identical phonemic percepts—the problem of “lack of invariance” (e.g., Liberman et al., 1952). The perception of these varying acoustic patterns was highly context-sensitive to preceding and following phonetic content in ways that appeared specific to the communicative constraints of speech and not applicable to the perception of other sounds—as in demonstrations of perceptual compensation for coarticulation, speaking rate normalization and talker normalization (e.g., Ladefoged and Broadbent, 1957; Miller and Liberman, 1979; Mann, 1980). One major source of evidence in favor of a Motor Theory account of speech perception is that information about a speaker’s production (anatomy or kinematics) from non-auditory sources can affect phonetic perception. The famed McGurk effect (McGurk and MacDonald, 1976), in which visual presentation of a talker can alter the auditory phonetic percept, is taken as evidence that listeners are integrating information about production from this secondary source. Fowler and Deckle (1991) have demonstrated a similar effect using haptic information gathered by touching the speaker’s face (see also Sato et al., 2010). Gick and Derrick (2009) reported that perception of consonant— vowel tokens in noise are biased toward voiceless stops (e.g., /pa/) when they are accompanied by a small burst of air on the skin of the listener, which could be interpreted as the aspiration that would more likely accompany the release of a voiceless stop. In addition, there have been several studies that have demonstrated that manipulations of the listener’s articulators can affect perception, which are supportive of the Motor Theory proposal that the mechanisms of production underlie the perception of speech. For example, Ito et al. (2009) obtained shifts in phoneme categorization resulting from external manipulation of the skin around the listener’s mouth in ways that would correspond to the deformations typical of producing these speech sounds (see also Yeung and Werker, 2013 for a similar demonstration with infants). Recently, Mochida et al. (2013) found that the ability to categorize consonants can be influenced by the simultaneous silent production of these consonants. Typically, these studies are proffered as evidence for a direct role of speech motor processing in speech perception. Independent of this proposed motor basis of perception, others have suggested the existence of a special speech or phonetic mode of perception based on evidence of neural and behavioral responses to the same stimuli being modulated by whether or not the listener believes the signal to be speech or non-speech (e.g., Tomiak et al., 1987; Vroomen and Baart, 2009; Stekelenburg and Vroomen, 2012).

Phase synchronization of instrumental music signals

Signal analysis is one of the finest scientific techniques in communication theory. Some quantitative and qualitative measures describe the pattern of a music signal, vary from one to another. Same musical recital, when played by different instrumentalists, generates different types of music patterns. The reason behind various patterns is the psychoacoustic measures - Dynamics, Timber, Tonality and Rhythm, varies in each time. However, the psycho-acoustic study of the music signals does not reveal any idea about the similarity between the signals. For such cases, study of synchronization of long-term nonlinear dynamics may provide effective results. In this context, phase synchronization (PS) is one of the measures to show synchronization between two non-identical signals. In fact, it is very critical to investigate any other kind of synchronization for experimental condition, because those are completely non identical signals. Also, there exists equivalence between the phases and the distances of the diagonal line in Recurrence plot (RP) of the signals, which is quantifiable by the recurrence quantification measure tau-recurrence rate. This paper considers two nonlinear music signals based on same raga played by two eminent sitar instrumentalists as two non-identical sources. The psycho-acoustic study shows how the Dynamics, Timber, Tonality and Rhythm vary for the two music signals. Then, long term analysis in the form of phase space reconstruction is performed, which reveals the chaotic phase spaces for both the signals. From the RP of both the phase spaces, tau-recurrence rate is calculated. Finally by the correlation of normalized tau-recurrence rate of their 3D phase spaces and the PS of the two music signals has been established. The numerical results well support the analysis.

The function of the basilar membrane and medial olivocochlear (MOC) reflex mimicked in a hearing aid algorithm

The hearing aid algorithm “BioAid” mimics two basic principles of normal hearing: the instantaneous compression of the basilar membrane and the efferent feedback of the medial olivocochlear (MOC) reflex. The design of this algorithm aims at restoring those parts of the auditory system, which are hypothesized to dysfunction in the individual listener. In the initial stage of this study individual computer models of three hearing-impaired listeners were constructed. These computer models reproduce the listeners’ performance in psychoacoustic measures of (1) absolute thresholds, (2) compression, and (3) frequency selectivity. Subsequently, these computer models were used as “artificial listeners.” Using BioAid as a front-end to the models, parameters of the algorithm were individually adjusted with the aim to ‘normalize’ the model performance on these psychoacoustic measures. In the final stage of the study, the optimized hearing aid fittings were evaluated with the three hearing-impaired listeners. The aided listeners showed the same qualitative characteristics of the psychoacoustic measures as the aided computer models: near-normal absolute thresholds, steeper compression estimates and sharper frequency selectivity curves. A systematic investigation of the effect of compression and the MOC feedback in the algorithm revealed that both are necessary to restore performance. [Work supported by DFG.]

Steady as /∫i/ goes: The spectral kinematics of sibilant fricatives in English and Japanese

Sibilant fricatives are often treated as having steady-state articulatory targets, which fix their spectra throughout their duration; however, Iskarous et al. (2011) reported that the centroid frequency of English /s/ varies considerably across the fricative's time course. This study replicates their spectral analysis using a psychoacoustic measure (peak ERB) and then extends it to English /∫/ and Japanese /s, ɕ/. The time-varying spectral pattern of each fricative was approximated with a nine-point peak ERB trajectory, computed from 20-ms windows spaced evenly throughout each token. There were three notable results. First, adults did not produce the same spectral kinematic pattern for all sibilants in a given language: the spectral peak of English /s/ followed a concave trajectory, while /∫/ remained relatively flat. Second, phonetically similar fricatives from different languages did not necessarily show similar dynamical spectral patterns: the peak trajectory of /s/ was curved in both languages, but re...

Reliable discrimination thresholds in 17 trials

This study explores potential weaknesses of the Zippy Estimation by Sequential Testing (ZEST) psychophysical procedure as a means of acquiring rapid psychoacoustic measurements. Although ZEST is promising for this purpose, previous work used a priori knowledge to make optimal choices for initial assumptions, a best case scenario for ZEST’s performance. Before the ZEST procedure can be employed as a clinical tool, an understanding of how it performs in the absence of a priori information is needed. Specifically, an investigator must choose: (1) the model psychometric function, (2) the starting level, and (3) the number of trials. The present study explores sensitivity to these choices when ZEST is employed in 2AFC, frequency-discrimination tasks. Data for six normal listeners were obtained for a wide range of initial conditions and compared with simulations. These data indicate that even when an inappropriate psychometric function is used, reliable thresholds can be obtained with only 17 trials when the starting level is within a factor of four times the listener’s “true” threshold. These results suggest that ZEST combined with a 2AFC paradigm is a promising candidate for rapid and reliable assessment of listeners' discrimination thresholds. [Work supported by NIH/NIDCD 1R03DC009071.]

The need for a soundscape taxonomy

It is for some time now that the standardization process in Soundscape in the ISO/TC 43/WG 54 12913 has started. Meanwhile, it has reached the level of decisions regarding evaluation approaches. Hence, as perception is the foreground of any assessment procedures here, on the one hand interviews do play a major role, but also procedures as sound walks. On the other hand, a time to evaluation related psychoacoustic measurement is needed to bring relevant datasets into triangulation. This paper will present the current state of the art in Soundscape and will discuss further input that is needed in this field.

Psychoacoustic Assessment to Improve Tinnitus Diagnosis

The diagnosis of tinnitus relies on self-report. Psychoacoustic measurements of tinnitus pitch and loudness are essential for assessing claims and discriminating true from false ones. For this reason, the quantification of tinnitus remains a challenging research goal. We aimed to: (1) assess the precision of a new tinnitus likeness rating procedure with a continuous-pitch presentation method, controlling for music training, and (2) test whether tinnitus psychoacoustic measurements have the sensitivity and specificity required to detect people faking tinnitus. Musicians and non-musicians with tinnitus, as well as simulated malingerers without tinnitus, were tested. Most were retested several weeks later. Tinnitus pitch matching was first assessed using the likeness rating method: pure tones from 0.25 to 16 kHz were presented randomly to participants, who had to rate the likeness of each tone to their tinnitus, and to adjust its level from 0 to 100 dB SPL. Tinnitus pitch matching was then assessed with a continuous-pitch method: participants had to match the pitch of their tinnitus to an external tone by moving their finger across a touch-sensitive strip, which generated a continuous pure tone from 0.5 to 20 kHz in 1-Hz steps. The predominant tinnitus pitch was consistent across both methods for both musicians and non-musicians, although musicians displayed better external tone pitch matching abilities. Simulated malingerers rated loudness much higher than did the other groups with a high degree of specificity (94.4%) and were unreliable in loudness (not pitch) matching from one session to the other. Retest data showed similar pitch matching responses for both methods for all participants. In conclusion, tinnitus pitch and loudness reliably correspond to the tinnitus percept, and psychoacoustic loudness matches are sensitive and specific to the presence of tinnitus.

Computer-Automated Tinnitus Assessment: Noise-Band Matching, Maskability, and Residual Inhibition

Psychoacoustic measures of tinnitus typically include loudness and pitch match, minimum masking level (MML), and residual inhibition (RI). We previously developed and documented a computer-automated tinnitus evaluation system (TES) capable of subject-guided loudness and pitch matching. The TES was further developed to conduct computer-aided, subject-guided testing for noise-band matching (NBM), MML, and RI. The purpose of the present study was to document the capability of the upgraded TES to obtain measures of NBM, MML, and RI, and to determine the test-retest reliability of the responses obtained. Three subject-guided, computer-automated testing protocols were developed to conduct NBM. For MML and RI testing, a 2-12 kHz band of noise was used. All testing was repeated during a second session. Subjects meeting study criteria were selected from those who had previously been tested for loudness and pitch matching in our laboratory. A total of 21 subjects completed testing, including seven females and 14 males. The upgraded TES was found to be fairly time efficient. Subjects were generally reliable, both within and between sessions, with respect to the type of stimulus they chose as the best match to their tinnitus. Matching to bandwidth was more variable between measurements, with greater consistency seen for subjects reporting tonal tinnitus or wide-band noisy tinnitus than intermediate types. Between-session repeated MMLs were within 10 dB of each other for all but three of the subjects. Subjects who experienced RI during Session 1 tended to be those who experienced it during Session 2. This study may represent the first time that NBM, MML, and RI audiometric testing results have been obtained entirely through a self-contained, computer-automated system designed specifically for use in the clinic. Future plans include refinements to achieve greater testing efficiency.

Relationship of distortion product otoacoustic emission components to psychoacoustic measures of noise induced hearing loss

Distortion product otoacoustic emissions (DPOAEs) have promise as a tool to detect and monitor cochlear hair cell damage in noise-induced hearing loss (NIHL). However, variability in OAE amplitudes and thresholds across individuals limits their potential for detecting the early impact of NIHL. The DPOAE has two components, one generated at the point of interaction between the primaries (generator), the second reflected from the characteristic place of the DPOAE frequency (reflected). This study investigated the components of the DPOAE and how they correlate with injury. A total of 109 men, including 54 with varying degrees of occupational noise exposure, were tested. We recorded DPOAEs using logarithmically swept pure-tones and extracted the components of the DPOAE using a least-squares fit approach. Audiometry was conducted at 1.5 and 4kHz with 1dB resolution. Compressive nonlinearity was evaluated psychoacoustically with 1.5 and 4kHz pure-tones using Schroeder-phase maskers. Overall there were associations between the generator component and the psychoacoustic measures: stronger DPOAE amplitudes were associated with better thresholds and greater difference in Schroeder-phase masking threshold. Associations were stronger at 4kHz than 1.5kHz. Similar, but weaker effects were observed for the reflected component. Findings suggest that separation of DPOAE components enhances the assessment of cochlear noise-induced injury.

A model-based hearing aid: Psychoacoustics, models, and algorithms

In hearing aids, amplification and dynamic range compression typically aim at compensating the deficits associated with outer-hair cell (OHC) loss. Nevertheless, success shows large inter-individual variability and hearing-impaired listeners generally still have considerable problems in complex acoustic communication situations including noise and reverberation. These problems could be related to inner-hair cell (IHC) damage and reduced frequency selectivity resulting in a loss of spectro-temporal coding fidelity. Here a model-based, fast-acting dynamic compression algorithm which aims at approximating the normal-hearing BM input-output function in hearing-impaired listeners is suggested. The algorithm is fitted by estimating low-level gain loss (OHC loss) from adaptive categorical loudness scaling data and audiometric thresholds based on Ewert and Grimm [Proc. ISAAR (2012)] and Jürgens et al. Hear. Res. 270, 177 (2011)]. Aided speech intelligibility was measured in stationary and fluctuating noise and related to the estimated OHC loss. To improve diagnostics of OHC and IHC loss, a series of five psychoacoustic measurements was conducted aiming at a direct quantification of IHC damage in a group of six young and elderly normal-hearing and 12 hearing-impaired listeners. A model is suggested to account for the temporal fine-structure detection and discrimination data. [Work funded by BMBF 01EZ0741 and DFG FOR1732.]

Bertram Scharf and his critical contributions to the field

Jerry Tobias introduced me to Bert Scharf via his book Foundations of Modern Auditory Theory. Our research in the 1970s was on the prediction of speech intelligibility from acoustic measurements; the similarity between Fletcher's 20 frequency bands of equal contributions to intelligibility and psychoacoustic measurements of critical bands was of great interest. Bert's chapter on critical bands provided an insightful, comprehensive, concise, and critical review of the state of the art in critical-band research. Our mutual research interests brought us together when he asked me to review a draft of a paper he was preparing. My review was highly critical and after submitting it to him I felt I had been too unforgiving in my review (reviewers can be wrong). I called him to explain that I had been overly critical of a fine paper. His response was the opposite of what I expected. He said it was the best review he had received and that he was extremely grateful for my input. I realized then that he—not only set high standards for others—but for himself as well. By adhering consistently to his high standards, his many contributions to the field have been long-lasting and critical.

Effect of musical training on static and dynamic measures of spectral-pattern discrimination

Both behavioral and physiological studies have demonstrated enhanced processing of speech in challenging listening environments attributable to musical training. The relationship, however, of this benefit to auditory abilities as assessed by psychoacoustic measures remains unclear. Using tasks previously shown to relate to speech-in-noise perception, the present study evaluated discrimination ability for static and dynamic spectral patterns by 49 listeners grouped as either musicians or nonmusicians. The two static conditions measured the ability to detect a change in the phase of a logarithmic sinusoidal spectral ripple of wideband noise with ripple densities of 1.5 and 3.0 cycles per octave chosen to emphasize either timbre or pitch distinctions, respectively. The dynamic conditions assessed temporal-pattern discrimination of 1-kHz pure tones frequency modulated by different 5-Hz lowpass noise samples with thresholds estimated in terms of either stimulus duration or signal-to-noise ratio. Musicians performed significantly better than nonmusicians on all four tasks. Discriminant analysis showed that group membership was correctly predicted for 84% of the listeners with the structure coefficient of each measure greater than 0.46. Results suggest that enhanced processing of static and dynamic spectral patterns defined by low-rate modulation may contribute to the relationship between musical training and speech-in-noise perception. [Work supported by NIH.]

Suprathreshold Auditory Processing and Speech Perception in Noise: Hearing-Impaired and Normal-Hearing Listeners

It is widely believed that suprathreshold distortions in auditory processing contribute to the speech recognition deficits experienced by hearing-impaired (HI) listeners in noise. Damage to outer hair cells and attendant reductions in peripheral compression and frequency selectivity may contribute to these deficits. In addition, reduced access to temporal fine structure (TFS) information in the speech waveform may play a role. To examine how measures of peripheral compression, frequency selectivity, and TFS sensitivity relate to speech recognition performance by HI listeners. To determine whether distortions in processing reflected by these psychoacoustic measures are more closely associated with speech deficits in steady-state or modulated noise. Normal-hearing (NH) and HI listeners were tested on tasks examining frequency selectivity (notched-noise task), peripheral compression (temporal masking curve task), and sensitivity to TFS information (frequency modulation [FM] detection task) in the presence of random amplitude modulation. Performance was tested at 500, 1000, 2000, and 4000 Hz at several presentation levels. The same listeners were tested on sentence recognition in steady-state and modulated noise at several signal-to-noise ratios. Ten NH and 18 HI listeners were tested. NH listeners ranged in age from 36 to 80 yr (M = 57.6). For HI listeners, ages ranged from 58 to 87 yr (M = 71.8). Scores on the FM detection task at 1 and 2 kHz were significantly correlated with speech scores in both noise conditions. Frequency selectivity and compression measures were not as clearly associated with speech performance. Speech Intelligibility Index (SII) analyses indicated only small differences in speech audibility across subjects for each signal-to-noise ratio (SNR) condition that would predict differences in speech scores no greater than 10% at a given SNR. Actual speech scores varied by as much as 80% across subjects. The results suggest that distorted processing of audible speech cues was a primary factor accounting for differences in speech scores across subjects and that reduced ability to use TFS cues may be an important component of this distortion. The influence of TFS cues on speech scores was comparable in steady-state and modulated noise. Speech recognition was not related to audibility, represented by the SII, once high-frequency sensitivity differences across subjects (beginning at 5 kHz) were removed statistically. This might indicate that high-frequency hearing loss is associated with distortions in processing in lower-frequency regions.

Psychoacoustic and Phoneme Identification Measures in Cochlear-Implant and Normal-Hearing Listeners

The purpose of this study is to identify precise and repeatable measures for assessing cochlear-implant (CI) hearing. The study presents psychoacoustic and phoneme identification measures in CI and normal-hearing (NH) listeners, with correlations between measures examined. Psychoacoustic measures included pitch discrimination tasks using pure tones, harmonic complexes, and tone pips; intensity perception tasks included intensity discrimination for tones and modulation detection; spectral-temporal masking tasks included gap detection, forward and backward masking, tone-on-tone masking, synthetic formant-on-formant masking, and tone in noise detection. Phoneme perception measures included vowel and consonant identification in quiet and stationary and temporally gated speech-shaped noise. Results on psychoacoustic measures illustrate the effects of broader filtering in CI hearing contributing to reduced pitch perception and increased spectral masking. Results on consonant and vowel identification measures illustrate a wide range in performance across CI listeners. They also provide further evidence that CI listeners obtain little to no release of masking in temporally gated noise compared to stationary noise. The forward and backward-masking measures had the highest correlation with the phoneme identification measures for CI listeners. No significant correlations between speech reception and psychoacoustic measures were observed for NH listeners. The superior NH performance on measures of phoneme identification, especially in the presence of background noise, is a key difference between groups.

The Effect of rTMS on Auditory Processing in Adults with Chronic, Bilateral Tinnitus: A Placebo-Controlled Pilot Study

BackgroundOn the basis that tinnitus may result from neural hyperactivity in the auditory cortex, researchers have investigated the use of low frequency (1 Hz) repetitive transcranial magnetic stimulation (rTMS) as a potential modulator of this hyperactivity. While these investigations show promise, investigations to date have neglected to consider the possible effect of 1 Hz rTMS on other functions of the auditory cortex of these individuals, such as auditory processing. Objective/hypothesisThis placebo-controlled pilot study aimed to determine whether 1 Hz rTMS applied to the primary auditory cortex (PAC), specifically Brodmann Area 41 (BA41), of adults with chronic, bilateral tinnitus would influence their auditory processing abilities. MethodsEight participants with bilateral, chronic tinnitus were randomized to receive a 10-day course of neuronavigationally guided active rTMS (n = 4) or placebo rTMS (n = 4) treatment applied to a focal region of the left PAC (BA41). Participants' auditory processing was measured using Time Compressed Reverberant Speech and three-pair Dichotic Digits (DD). Their tinnitus was measured using the Tinnitus Handicap Inventory (THI) and a psychoacoustic measure of tinnitus perception. All outcome measures were administered at baseline (1 week prior to rTMS), 1 week, 1, 2 and 3 months post-rTMS. ResultsAll four participants in the active rTMS (A) group, and none of the participants in the sham (placebo) rTMS (S) group, showed improved auditory processing scores at multiple assessment points post-stimulation, with the group differences in median normalized gain scores reaching significance at the 5% level from 1 week or 1 month post-stimulation onwards. Three of the four participants in the active rTMS (A) group, and none of the participants in the sham rTMS (S) group, showed improved tinnitus scores at multiple assessment points post-stimulation, with some of the group differences in median normalized gain scores reaching significance at the 5% level. ConclusionsThe results of this preliminary study suggest that 1 Hz rTMS applied to the PAC (BA41) has the capacity to improve both auditory processing and tinnitus perception in some adults with chronic, bilateral tinnitus.