Thoughts about Suicide and Self-Harm in Patients with Tinnitus and Hyperacusis

There are conflicting reports with regard to the relationship between suicidal ideations and tinnitus and hyperacusis. Audiology departments play a major role in offering therapy and support for patients experiencing tinnitus and hyperacusis. If suicidal and self-harm ideations among patients seen in audiology clinics are high, then it would be important to screen for them to make onward referrals to mental health services.

The aim of this study was to assess the prevalence of and factors related to suicidal and self-harm ideations in patients with tinnitus and hyperacusis seen at an audiology outpatient service.

This study was a part of a service evaluation survey using a correlational design.

All patients who sought help concerning their tinnitus or hyperacusis from an audiology clinic of the National Health Service in the United Kingdom in a 1-yr period were asked to complete the survey questionnaires (n = 402).

The focus of this article is on analysis of the patients’ responses about suicidal and self-harm ideations as measured via the Patient Health Questionnaire, item 9, and their associated factors.

A total of 150/402 of patients answered the question about suicidal and self-harm ideations. Of these, 13% indicated that they had suicidal or self-harm ideations in the past 2 weeks. Suicidal and self-harm ideations were moderately correlated with scores on the anxiety and depression subscales of the hospital anxiety and depression scale. Suicidal and self-harm ideations decreased with increasing age. There were small statistically significant correlations between suicidal and self-harm ideations and tinnitus handicap, hyperacusis handicap, insomnia, and scores on the visual analog scale (VAS) of effect of tinnitus on life. The correlations between suicidal and self-harm ideations and gender, pure-tone average of the worse and better ears, uncomfortable loudness levels of the worse ears, and VAS of tinnitus loudness and annoyance were not statistically significant. A regression model showed that abnormal depression scores increased the chance of suicidal and self-harm ideations by a factor of 6.2 (95% confidence interval = 1.13–34.1, p = 0.036).

Audiologists offering tinnitus and hyperacusis rehabilitation should screen for suicidal and self-harm ideations among patients, especially for those with comorbid depression, and make onward referral to appropriate services when needed.

Factors Related to Insomnia in Adult Patients with Tinnitus and/or Hyperacusis: An Exploratory Analysis

People with tinnitus and/or hyperacusis often experience insomnia. However, it is unclear what factors are most strongly associated with insomnia.

To explore factors related to insomnia in patients with tinnitus and/or hyperacusis.

This was a retrospective study using multiple-regression analysis.

Data were assessed for 444 consecutive patients who sought help concerning their tinnitus and/or hyperacusis from a specialist audiology center in the UK National Health Service. The average age of the patients was 54 years (standard deviation = 15 years).

The results of audiological tests and self-report questionnaires were gathered retrospectively from the records of the patients. Multiple-regression analysis was used to assess the relationship between insomnia and other variables.

Sixty-nine percent of patients with tinnitus experienced some form of insomnia as measured via the Insomnia Severity Index (ISI). A multiple-regression model showed that ISI scores were significantly associated with depression scores measured via the depression subscale of the Hospital Anxiety and Depression Scale (HADS) (regression coefficient [b] = 0.44, p < 0.001), tinnitus annoyance measured via the visual analog scale (VAS) (b = 0.49, p = 0.001), anxiety measured via the anxiety subscale of the HADS (b = 0.21, p = 0.012), and tinnitus handicap measured via the Tinnitus Handicap Inventory (b = 0.07, p < 0.001). The model explained 45% of the variance in ISI scores. VAS scores for tinnitus loudness, hyperacusis-related measures, hearing thresholds, age, and gender were not significantly related to insomnia.

The prevalence of insomnia in patients with tinnitus is high. Both tinnitus-related factors and psychological factors are related to the severity of insomnia. Hyperacusis is not significantly associated with insomnia.

Parental Mental Health in Childhood as a Risk Factor for Anxiety and Depression among People Seeking Help for Tinnitus and Hyperacusis

Parental mental illness is a risk factor for mental health disorders in the offspring. However, the relationship between parental illness in childhood and mental health disorders in adulthood among patients with tinnitus and/or hyperacusis is not known.

The aim was to explore the relationship between parental mental health in childhood and anxiety and depression for patients experiencing tinnitus and/or hyperacusis.

This was a retrospective cross-sectional study with a correlational design.

Two hundred eighty-seven consecutive patients who attended a Tinnitus and Hyperacusis Therapy Specialist Clinic in the United Kingdom were included. Their average age was 52.5 years.

The association was explored between anxiety and depression measured via the Generalized Anxiety Disorder questionnaire (GAD-7) and the Patient Health questionnaire (PHQ-9) and responses to the question “While you were growing up during the first 18 years of life did your parent(s) have depression or mental illness?”

Thirty-nine percent of patients (111/287) responded “yes” to the question about their parents’ mental health, which is about double the incidence in the general population. Regression analysis showed that parental mental illness significantly increased the risk of anxiety and depression, with unadjusted odds ratios (ORs) of 2.7 (95% confidence interval [CI]: 1.5–4.9, p = 0.001) for the PHQ-9 and 2.6 (95% CI: 1.4–4.8, p = 0.002) for the GAD-7. However, when the models were adjusted for the effects of age, gender, tinnitus handicap as measured via the Tinnitus Handicap Inventory, hyperacusis handicap as measured via the Hyperacusis questionnaire, uncomfortable loudness levels, GAD-7 scores (for the depression model only), and PHQ-9 scores (for the anxiety model only), parental mental health was only significantly associated with depression, with an OR of 2.7 (95% CI: 1.08–6.7, p = 0.033).

Audiologists offering tinnitus and hyperacusis rehabilitation should screen patients for parental mental illness in childhood, especially for those with comorbid depression, and make onward referral to appropriate mental health services when needed. Future research should analyze the breadth and type of adverse childhood experiences among patients with tinnitus and hyperacusis and their relationship with mental problems and treatment efficacy.

Parental Separation and Parental Mental Health in Childhood and Risk of Insomnia in Adulthood among Patients with Tinnitus

Many patients seeking help for tinnitus also suffer from insomnia. Adverse childhood experiences may affect the likelihood of insomnia in later life for such patients.

To explore whether parental separation and parental mental health during childhood are related to the severity of insomnia among patients with tinnitus and/or hyperacusis seen in an Audiology clinic.

This was a retrospective cross-sectional study.

One hundred seventy-four consecutive patients who attended a tinnitus/hyperacusis clinic in the United Kingdom were included.

Data were based on responses to questionnaires for people seeking help for tinnitus.

Sixteen percent of patients (27/174) reported that during the first 18 years of life, their parents were separated or divorced and 41% (72/174) reported that their parent(s) suffered from a mental illness. The mean score for the insomnia severity index (ISI) was not significantly affected by parental separation or divorce. However, the mean ISI score was significantly worse for patients whose parents had a mental illness. A multinomial logistic regression model, adjusted for the presence of hyperacusis, hearing loss, age, and gender, indicated that for individuals experiencing tinnitus, a history of parental mental illness during their childhood increased the chance of severe insomnia by a factor of 3.4 (95% confidence interval: 1.1 to 10.8, p = 0.04). The risk of having severe insomnia was 3.8 times greater for patients with hyperacusis than for those without.

Among patients seeking help for tinnitus/hyperacusis, poor parental mental health was associated with severe insomnia.

Effects of hearing loss and age on the binaural processing of temporal envelope and temporal fine structure information

Within the cochlea, broadband sounds like speech and music are filtered into a series of narrowband signals, each with a relatively slowly varying envelope (ENV) imposed on a rapidly oscillating carrier (the temporal fine structure, TFS). Information about ENV is conveyed by the timing and short-term rate of action potentials in the auditory nerve while information about TFS is conveyed by synchronization of action potentials to a specific phase of the waveform in the cochlea (phase locking). This paper describes the effects of age and hearing loss on the binaural processing of ENV and TFS information, i.e. on the processing of differences in ENV and TFS at the two ears. The binaural processing of TFS information is adversely affected by both hearing loss and increasing age. The binaural processing of ENV information deteriorates somewhat with increasing age but is only slightly affected by hearing loss. The reduced TFS processing abilities found for older/hearing-impaired subjects may partially account for the difficulties that such subjects experience in complex listening situations when the target speech and interfering sounds come from different directions in space.

The accuracy of auditory spatial judgments in the visually impaired is dependent on sound source distance

Blindness leads to substantial enhancements in many auditory abilities, and deficits in others. It is unknown how severe visual losses need to be before changes in auditory abilities occur, or whether the relationship between severity of visual loss and changes in auditory abilities is proportional and systematic. Here we show that greater severity of visual loss is associated with increased auditory judgments of distance and room size. On average participants with severe visual losses perceived sounds to be twice as far away, and rooms to be three times larger, than sighted controls. Distance estimates for sighted controls were most accurate for closer sounds and least accurate for farther sounds. As the severity of visual impairment increased, accuracy decreased for closer sounds and increased for farther sounds. However, it is for closer sounds that accurate judgments are needed to guide rapid motor responses to auditory events, e.g. planning a safe path through a busy street to avoid collisions with other people, and falls. Interestingly, greater visual impairment severity was associated with more accurate room size estimates. The results support a new hypothesis that crossmodal calibration of audition by vision depends on the severity of visual loss.

Comparison of auditory spatial bisection and minimum audible angle in front, lateral, and back space

Although vision is important for calibrating auditory spatial perception, it only provides information about frontal sound sources. Previous studies of blind and sighted people support the idea that azimuthal spatial bisection in frontal space requires visual calibration, while detection of a change in azimuth (minimum audible angle, MAA) does not. The influence of vision on the ability to map frontal, lateral and back space has not been investigated. Performance in spatial bisection and MAA tasks was assessed for normally sighted blindfolded subjects using bursts of white noise presented frontally, laterally, or from the back relative to the subjects. Thresholds for both tasks were similar in frontal space, lower for the MAA task than for the bisection task in back space, and higher for the MAA task in lateral space. Two interpretations of the results are discussed, one in terms of visual calibration and the use of internal representations of source location and the other based on comparison of the magnitude or direction of change of the available binaural cues. That bisection thresholds were increased in back space relative to front space, where visual calibration information is unavailable, suggests that an internal representation of source location was used for the bisection task.

Effect of the number of amplitude-compression channels and compression speed on speech recognition by listeners with mild to moderate sensorineural hearing loss

The use of a large number of amplitude-compression channels in hearing aids has potential advantages, such as the ability to compensate for variations in loudness recruitment across frequency and provide appropriate frequency-response shaping. However, sound quality and speech intelligibility could be adversely affected due to reduction of spectro-temporal contrast and distortion, especially when fast-acting compression is used. This study assessed the effect of the number of channels and compression speed on speech recognition when the multichannel processing was used solely to implement amplitude compression, and not for frequency-response shaping. Computer-simulated hearing aids were used. The frequency-dependent insertion gains for speech with a level of 65 dB sound pressure level were applied using a single filter before the signal was filtered into compression channels. Fast-acting (attack, 10 ms; release, 100 ms) or slow-acting (attack, 50 ms; release, 3000 ms) compression using 3, 6, 12, and 22 channels was applied subsequently. Using a sentence recognition task with speech in two- and eight-talker babble at three different signal-to-babble ratios (SBRs), 20 adults with sensorineural hearing loss were tested. The number of channels and compression speed had no significant effect on speech recognition, regardless of babble type or SBR.

Narrow-band ripple glide direction discrimination and its relationship to frequency selectivity estimated using psychophysical tuning curves

The highest spectral ripple density at which the discrimination of ripple glide direction was possible (STRt_dir task) was assessed for one-octave wide (narrowband) stimuli with center frequencies of 500, 1000, 2000, and 4000 Hz and for a broadband stimulus. A pink noise lowpass filtered at the lower edge frequency of the rippled-noise stimuli was used to mask possible combination ripples. The relationship between thresholds measured using the STRt_dir task and estimates of the sharpness of tuning (Q10) derived from fast psychophysical tuning curves was assessed for subjects with normal hearing (NH) and cochlear hearing loss (CHL). The STRt_dir thresholds for the narrowband stimuli were highly correlated with Q10 values for the same center frequency, supporting the idea that STRt_dir thresholds for the narrowband stimuli provide a good measure of frequency resolution. Both the STRt_dir thresholds and the Q10 values were lower (worse) for the subjects with CHL than for the subjects with NH. For both the NH and CHL subjects, mean STRt_dir thresholds for the broadband stimulus were not significantly higher (better) than for the narrowband stimuli, suggesting little or no ability to combine information across center frequencies.

No Effect of Musical Training on Frequency Selectivity Estimated Using Three Methods

It is widely believed that the frequency selectivity of the auditory system is largely determined by processes occurring in the cochlea. If so, musical training would not be expected to influence frequency selectivity. Consistent with this, auditory filter shapes for low center frequencies do not differ for musicians and nonmusicians. However, it has been reported that psychophysical tuning curves (PTCs) at 4000 Hz were sharper for musicians than for nonmusicians. This study explored the origin of the discrepancy across studies. Frequency selectivity was estimated for musicians and nonmusicians using three methods: fast PTCs with a masker that swept in frequency, "traditional" PTCs obtained using several fixed masker center frequencies, and the notched-noise method. The signal frequency was 4000 Hz. The data were fitted assuming that each side of the auditory filter had the shape of a rounded-exponential function. The sharpness of the auditory filters, estimated as the Q₁₀ values, did not differ significantly between musicians and nonmusicians for any of the methods, but detection efficiency tended to be higher for the musicians. This is consistent with the idea that musicianship influences auditory proficiency but does not influence the peripheral processes that determine the frequency selectivity of the auditory system.

Psychoacoustic Aspects of Speech Pattern Coding for the Deaf

The SiVo aid, which provides a sinusoidal signal indicating voice fundamental frequency and voicing information, was compared as an aid to lipreading to a conventional hearing aid having extended low-frequency output. Speech perceptual measures of consonant confusions in lipreading and the identification of a simple intonation contrast were collected from a group of 8 profoundly deaf adults. Audiometric and psychoacoustic measures were also collected. In the intonation task, 6 of the 7 patients tested performed better with the SiVo aid and the seventh scored perfectly with both aids. Four patients (out of 8) preferred to use the SiVo aid rather than the conventional aid, and 2 of these showed a significant advantage with the SiVo aid in the aided lipreading of consonants. The remaining 4 patients preferred the conventional aid, although none of these patients showed a significant advantage with the conventional aid in the lipreading of consonants. The 4 patients who preferred the SiVo aid over the conventional aid had very profound hearing loss and minimal dynamic range at 500 Hz and above, and those receiving the greatest benefit showed no measurable frequency selectivity. In the 2 patients who preferred the SiVo aid, yet showed no significant advantage for the SiVo aid in consonant lipreading, consonant confusions were also measured for aided lipreading, using a prototype aid providing both voice fundamental frequency and voiceless excitation patterns. Both patients showed additional and significant benefit from inclusion of the voiceless pattern element.

How Much Do We Gain by Gain Control in Hearing Aids?

This paper considers three rationales for the use of automatic gain control (AGC) in hearing aids, and particularly multi-channel AGC. One rationale is to restore loudness relations among the acoustical elements of speech to what they would be for a normal ear. At present, there seems to be little evidence to support the idea that such loudness relations are critical for speech intelligibility. A second rationale is to reduce the effects of narrowband interfering sounds. This may be applicable in some restricted situations, but not in many others. The third rationale, the one considered here to be most important, is to ensure that all of the important elements in speech are comfortably audible. This can be achieved using two forms of AGC: slow-acting AGC operating on the whole speech signal, to compensate for variations in overall sound level from one situation to another; and fast-acting (syllabic) compression acting independently in a number of bands, to compensate for differences in level of acoustical elements within speech. To reduce spectral and temporal distortions introduced by the syllabic compression, the number of bands should be small (probably two or three) and the amount of compression should be the minimum required to ensure that all of the important elements in speech are audible. It is concluded that gain control can be useful for increasing user comfort and for ensuring the audibility of speech sounds. It is not likely to restore impaired hearing to normal for most patients, but may usefully be employed in conjunction with other forms of signal processing.

Patients' Perspectives About the Acceptability and Effectiveness of Audiologist-Delivered Cognitive Behavioral Therapy for Tinnitus and/or Hyperacusis Rehabilitation

Objective The aim of this study was to evaluate the views of patients who completed audiologist-delivered cognitive behavioral therapy (CBT) about (a) the effectiveness of the treatment, (b) the acceptability of receiving CBT from audiologists, and (c) the most effective treatment components. Design This was a service evaluation survey with a cross-sectional design. Study Sample The study population comprised 40 consecutive adult patients who received a full course of audiologist-delivered CBT for tinnitus and/or hyperacusis management at a Tinnitus and Hyperacusis Therapy Specialist Clinic in the United Kingdom over a 1-year period. Thirty-one of 40 patients who attended their final session as planned completed the survey questionnaire. Data Collection and Analysis As a part of their routine care, all patients completed a wide range of questionnaires before and after receiving audiologist-delivered CBT. These comprised Tinnitus Handicap Inventory (Newman, Sandridge, & Bolek, 2008); Hyperacusis Questionnaire (Khalfa et al., 2002); Insomnia Severity Index (Bastien, Vallieres, & Morin, 2001); Visual Analogue Scale (Maxwell, 1978) for tinnitus loudness, tinnitus annoyance, and effect of tinnitus on life; Generalized Anxiety Disorder (Spitzer, Kroenke, Williams, & Lowe, 2006) questionnaire; and Patient Health Questionnaire (Kroenke, Spitzer, & Williams, 2001). In addition, patients were asked to complete the survey questionnaire at their final session to provide feedback with regard to their therapy. Results The majority of patients reported that it was very acceptable to them to receive CBT focused on tinnitus and hyperacusis from a specialist audiologist; the median response was 10/10. The majority of patients felt that the CBT was very effective (median response 8/10) and that they were able to manage their tinnitus and/or hyperacusis well (median response 9/10). The effect sizes of treatment based on pre- and postintervention comparison of scores for the Tinnitus Handicap Inventory, Visual Analogue Scale of tinnitus annoyance and effect on life, Hyperacusis Questionnaire, Insomnia Severity Index, Generalized Anxiety Disorder, and Patient Health Questionnaire were large. Conclusions Audiologist-delivered CBT is acceptable to patients and is effective in the management of tinnitus and/or hyperacusis from the patients' perspectives.

Comparison of Frequency Transposition and Frequency Compression for People With Extensive Dead Regions in the Cochlea

The objective was to determine the effects of two frequency-lowering algorithms (frequency transposition, FT, and frequency compression, FC) on audibility, speech identification, and subjective benefit, for people with high-frequency hearing loss and extensive dead regions (DRs) in the cochlea. A single-blind randomized crossover design was used. FT and FC were compared with each other and with a control condition (denoted ‘Control’) without frequency lowering, using hearing aids that were otherwise identical. Data were collected after at least 6 weeks of experience with a condition. Outcome measures were audibility, scores for consonant identification, scores for word-final /s, z/ detection (S test), sentence-in-noise intelligibility, and a questionnaire assessing self-perceived benefit (Spatial and Qualities of Hearing Scale). Ten adults with steeply sloping high-frequency hearing loss and extensive DRs were tested. FT and FC improved the audibility of some high-frequency sounds for 7 and 9 participants out of 10, respectively. At the group level, performance for FT and FC did not differ significantly from that for Control for any of the outcome measures. However, the pattern of consonant confusions varied across conditions. Bayesian analysis of the confusion matrices revealed a trend for FT to lead to more consistent error patterns than FC and Control. Thus, FT may have the potential to give greater benefit than Control or FC following extended experience or training.

Discrimination of the phase of amplitude modulation applied to different carriers: Effects of modulation rate and modulation depth for young and older subjects

The discrimination of amplitude modulation (AM) from frequency modulation (FM) of a 1000-Hz carrier, with equally detectable AM and FM, is better for a 2-Hz than for a 10-Hz modulation rate. This might reflect greater sensitivity to temporal fine structure for low than for high rates. Alternatively, AM-FM discrimination may depend on comparing fluctuations in excitation level on the two sides of the excitation pattern, which are in phase for AM and out of phase for FM. Discrimination of the relative phase of fluctuations might worsen with increasing rate, which could account for the effect of rate on AM-FM discrimination. To test this, discrimination of the phase of AM applied to two sinusoidal carriers was assessed, with a band of noise between the two carriers to prevent use of within-channel cues. Young and older subjects with normal hearing were tested. Performance was almost constant for AM rates from 2 to 10 Hz, but worsened at 20 Hz. Performance was near chance for AM depths near the detection threshold. The results suggest that the superior AM-FM discrimination at 2 Hz cannot be explained in terms of comparison of the phase of fluctuations on the two sides of the excitation pattern.

On the loudness of low-frequency sounds with fluctuating amplitudes

Some environmental sounds have strong amplitude fluctuations that may affect their perceived loudness and annoyance. This study assessed the effect of beat rate (f_b) and center frequency (f_c) on the loudness of low-frequency beating tones. The loudness of two-tone complexes (TTCs) with f_c = 40, 63, 80, and 1000 Hz was matched with that of unmodulated tones (UTs). Frequency differences between the TTC components, corresponding to f_b = 1, 2, 5, and 12 Hz, were used. To compensate for the steep decline in hearing sensitivity below 100 Hz, prior to the loudness match, subjects adjusted the relative levels (ΔL) of the TTC components to give maximum beat perception. Twenty-four normal-hearing subjects were tested. The values of ΔL giving best beats were well predicted from the transfer function of the middle ear and the estimated shapes of the auditory filters, assuming that the auditory filter whose output dominated the beat percept was centered somewhat above f_c. At the same root-mean-square level and independent of f_c, TTCs were perceived as louder than UTs for f_b ≤ 2 Hz, had roughly equal loudness to UTs for f_b = 5 Hz, and were less loud than UTs for f_b = 12 Hz.

Effect of age on envelope regularity discrimination

The ability to discriminate irregular from regular amplitude modulation was compared for young and older adults with audiometric thresholds within the normal range for frequencies from 250 to 8000 Hz, using the "envelope regularity discrimination" (ERD) test. The amount of irregularity was parametrically varied and quantified by an "irregularity index." The carrier frequency was 2000 Hz, the modulation rate was 8 Hz, and the baseline modulation index was 0.3. Stimuli were presented both at 80 dB sound pressure level (SPL) and at 20 dB sensation level (SL) in the presence of a threshold-equalizing noise. There was a significant effect of level, performance being better at 80 dB SPL than at 20 dB SL. There was also a significant effect of age, performance being worse for the older subjects. There was no significant interaction of level and age. The thresholds for the ERD test were not significantly correlated with absolute thresholds at the test carrier frequency of 2000 Hz, for either group, or for the two groups combined. The worse envelope regularity discrimination for the older group may be related to the age-related synaptopathy that has been established from recent studies of human temporal bones.

The effect of musicianship, contralateral noise, and ear of presentation on the detection of changes in temporal fine structure

Musicians are better than non-musicians at discriminating changes in the fundamental frequency (F0) of harmonic complex tones. Such discrimination may be based on place cues derived from low resolved harmonics, envelope cues derived from high harmonics, and temporal fine structure (TFS) cues derived from both low and high harmonics. The present study compared the ability of highly trained violinists and non-musicians to discriminate changes in complex sounds that differed primarily in their TFS. The task was to discriminate harmonic (H) and frequency-shifted inharmonic (I) tones that were bandpass filtered such that the components were largely or completely unresolved. The effect of contralateral noise and ear of presentation was also investigated. It was hypothesized that contralateral noise would activate the efferent system, helping to preserve the neural representation of envelope fluctuations in the H and I stimuli, thereby improving their discrimination. Violinists were significantly better than non-musicians at discriminating the H and I tones. However, contralateral noise and ear of presentation had no effect. It is concluded that, compared to non-musicians, violinists have a superior ability to discriminate complex sounds based on their TFS, and this ability is unaffected by contralateral stimulation or ear of presentation.

Using recurrent neural networks to improve the perception of speech in non-stationary noise by people with cochlear implants

Speech-in-noise perception is a major problem for users of cochlear implants (CIs), especially with non-stationary background noise. Noise-reduction algorithms have produced benefits but relied on a priori information about the target speaker and/or background noise. A recurrent neural network (RNN) algorithm was developed for enhancing speech in non-stationary noise and its benefits were evaluated for speech perception, using both objective measures and experiments with CI simulations and CI users. The RNN was trained using speech from many talkers mixed with multi-talker or traffic noise recordings. Its performance was evaluated using speech from an unseen talker mixed with different noise recordings of the same class, either babble or traffic noise. Objective measures indicated benefits of using a recurrent over a feed-forward architecture, and predicted better speech intelligibility with than without the processing. The experimental results showed significantly improved intelligibility of speech in babble noise but not in traffic noise. CI subjects rated the processed stimuli as significantly better in terms of speech distortions, noise intrusiveness, and overall quality than unprocessed stimuli for both babble and traffic noise. These results extend previous findings for CI users to mostly unseen acoustic conditions with non-stationary noise.

Envelope regularity discrimination

The ability to discriminate irregular from regular amplitude modulation was assessed using the "envelope regularity discrimination" test. The amount of irregularity was parametrically varied and quantified by an "irregularity index." Normative data were gathered for young subjects with normal audiometric thresholds. Parameters varied were the carrier and modulation frequencies, f_c and f_m, and the baseline modulation index, m. All tests were performed using a background threshold-equalizing noise. The main findings were (1) using f_c = 4000 Hz, f_m = 8 Hz, and m = 0.3, performance improved over the first two threshold runs and then remained roughly stable, and there was a high correlation between thresholds obtained at 80 dB sound pressure level (SPL) and at 20 dB sensation level; (2) using f_m = 8 Hz and m = 0.3 with a level of 80 dB SPL, thresholds did not vary significantly across f_c = 1000, 2000, and 4000 Hz; (3) using f_m = 8 Hz and f_c = 4000 Hz with a level of 80 dB SPL, thresholds did not vary significantly for m from 0.2 to 0.5; and (4) using m = 0.3 and f_c = 4000 Hz with a level of 80 dB SPL, thresholds improved with increasing f_m from 2 to 16 Hz. For all conditions, there was substantial individual variability, probably resulting from differences in "processing efficiency."

Effect of ripple repetition rate on discrimination of ripple glide direction and the detection of brief tones in spectro-temporal ripple noise

The effect of temporal repetition rate R on the discrimination and internal representation of stimuli with spectro-temporal ripples was examined. Experiment 1 measured the highest ripple density D at which upward- and downward-gliding ripples could be discriminated. Thresholds varied only slightly for R from 2 to 8 Hz, with a median threshold just above 5 ripples/oct. The threshold decreased (worsened) when R was increased to 16 and 32 Hz, suggesting that the limited temporal resolution of the auditory system plays a role for these higher values of R. Experiment 2 explored the internal representation of stimuli with static and downward-gliding spectral ripples by measuring the detection threshold for a brief tone presented at a peak or a valley in the stimulus spectrum. Thresholds were generally higher when the signal was at a peak than when it was at a valley. The peak-valley difference tended to decrease with increasing D, and the variation of thresholds with D was greater for low R than for high R. The results suggest that the discrimination of spectro-temporal ripples is limited mainly by frequency resolution for lower ripple rates (up to 4-8 Hz) but temporal resolution plays a major role for higher rates.

Speech Processing to Improve the Perception of Speech in Background Noise for Children With Auditory Processing Disorder and Typically Developing Peers

Auditory processing disorder (APD) may be diagnosed when a child has listening difficulties but has normal audiometric thresholds. For adults with normal hearing and with mild-to-moderate hearing impairment, an algorithm called spectral shaping with dynamic range compression (SSDRC) has been shown to increase the intelligibility of speech when background noise is added after the processing. Here, we assessed the effect of such processing using 8 children with APD and 10 age-matched control children. The loudness of the processed and unprocessed sentences was matched using a loudness model. The task was to repeat back sentences produced by a female speaker when presented with either speech-shaped noise (SSN) or a male competing speaker (CS) at two signal-to-background ratios (SBRs). Speech identification was significantly better with SSDRC processing than without, for both groups. The benefit of SSDRC processing was greater for the SSN than for the CS background. For the SSN, scores were similar for the two groups at both SBRs. For the CS, the APD group performed significantly more poorly than the control group. The overall improvement produced by SSDRC processing could be useful for enhancing communication in a classroom where the teacher's voice is broadcast using a wireless system.

Comparison of effects on subjective intelligibility and quality of speech in babble for two algorithms: A deep recurrent neural network and spectral subtraction

The effects on speech intelligibility and sound quality of two noise-reduction algorithms were compared: a deep recurrent neural network (RNN) and spectral subtraction (SS). The RNN was trained using sentences spoken by a large number of talkers with a variety of accents, presented in babble. Different talkers were used for testing. Participants with mild-to-moderate hearing loss were tested. Stimuli were given frequency-dependent linear amplification to compensate for the individual hearing losses. A paired-comparison procedure was used to compare all possible combinations of three conditions. The conditions were: speech in babble with no processing (NP) or processed using the RNN or SS. In each trial, the same sentence was played twice using two different conditions. The participants indicated which one was better and by how much in terms of speech intelligibility and (in separate blocks) sound quality. Processing using the RNN was significantly preferred over NP and over SS processing for both subjective intelligibility and sound quality, although the magnitude of the preferences was small. SS processing was not significantly preferred over NP for either subjective intelligibility or sound quality. Objective computational measures of speech intelligibility predicted better intelligibility for RNN than for SS or NP.