S. Theo Goverts

Auditory and nonauditory factors affecting speech reception in noise by older listeners

Speech reception thresholds (SRTs) for sentences were determined in stationary and modulated background noise for two age-matched groups of normal-hearing (N = 13) and hearing-impaired listeners (N = 21). Correlations were studied between the SRT in noise and measures of auditory and nonauditory performance, after which stepwise regression analyses were performed within both groups separately. Auditory measures included the pure-tone audiogram and tests of spectral and temporal acuity. Nonauditory factors were assessed by measuring the text reception threshold (TRT), a visual analogue of the SRT, in which partially masked sentences were adaptively presented. Results indicate that, for the normal-hearing group, the variance in speech reception is mainly associated with nonauditory factors, both in stationary and in modulated noise. For the hearing-impaired group, speech reception in stationary noise is mainly related to the audiogram, even when audibility effects are accounted for. In modulated noise, both auditory (temporal acuity) and nonauditory factors (TRT) contribute to explaining interindividual differences in speech reception. Age was not a significant factor in the results. It is concluded that, under some conditions, nonauditory factors are relevant for the perception of speech in noise. Further evaluation of nonauditory factors might enable adapting the expectations from auditory rehabilitation in clinical settings.

Hearing status, need for recovery after work, and psychosocial work characteristics: results from an internet-based national survey on hearing

The main aim of the study is to address the relationship between hearing status and need for recovery. In addition, the role of hearing status in the relationship between psychosocial work characteristics (i.e. job demands and job control) and need for recovery was assessed. The sample comprised 925 normally-hearing and hearing-impaired working adults (aged 18–65 years) participating in the National Longitudinal Study on Hearing. Hearing status was determined using the national hearing (speech-in-noise) test over the internet. Psychosocial work characteristics and need for recovery were assessed using the job content questionnaire and the Dutch questionnaire on the experience and assessment of work. Regression models revealed a significant association between hearing status and need for recovery after work, poorer hearing leading to an increasing need for recovery. Additionally, poorer hearing led to a higher odds for risky levels of need for recovery. Hearing status did not influence the significant relationship between psychosocial work characteristics (i.e. job demand and job control) and need for recovery after work. Implications for clinical practice, such as the necessity of having adequate enablement programs for this specific group of patients, are discussed.

The digits-in-noise test: Assessing auditory speech recognition abilities in noise

A speech-in-noise test which uses digit triplets in steady-state speech noise was developed. The test measures primarily the auditory, or bottom-up, speech recognition abilities in noise. Digit triplets were formed by concatenating single digits spoken by a male speaker. Level corrections were made to individual digits to create a set of homogeneous digit triplets with steep speech recognition functions. The test measures the speech reception threshold (SRT) in long-term average speech-spectrum noise via a 1-up, 1-down adaptive procedure with a measurement error of 0.7 dB. One training list is needed for naive listeners. No further learning effects were observed in 24 subsequent SRT measurements. The test was validated by comparing results on the test with results on the standard sentences-in-noise test. To avoid the confounding of hearing loss, age, and linguistic skills, these measurements were performed in normal-hearing subjects with simulated hearing loss. The signals were spectrally smeared and/or low-pass filtered at varying cutoff frequencies. After correction for measurement error the correlation coefficient between SRTs measured with both tests equaled 0.96. Finally, the feasibility of the test was approved in a study where reference SRT values were gathered in a representative set of 1386 listeners over 60 years of age.

A prospective multi-centre study of the benefits of bilateral hearing aids.

Objectives: In this prospective study the benefits of a second hearing aid were evaluated objectively (functional tests) and subjectively (questionnaires). In addition, a battery of diagnostic tests (by headphones) was applied to determine whether the bilateral benefit could be predicted from a priori tests. Design: Diagnostic tests by headphones (binaural masking level difference, interaural time difference, and speech reception thresholds per ear) were conducted to focus on binaural functioning, and free-field tests were used for unilateral and bilateral hearing aids in the same participants to analyze differences in speech intelligibility and horizontal localization. The participants were recruited from the regular patients for hearing aid fitting in eight Audiological Centers. Eventually, 214 participants participated in this study. Each of these participants was fitted with two new hearing aids and started a trial period. Before the trial period the headphone tests were conducted, after the trial period the free-field tests were conducted with one and two hearing aids, and the participants completed a questionnaire. Results and Conclusions: In a number of respects bilaterally fitted hearing aids offered a benefit relative to unilaterally fitted hearing aids (the so-called bilateral benefit), both subjectively (questionnaire) and objectively (speech perception in noise and localization). However, we found large interindividual differences and not all differences were clinically relevant. The results of the diagnostic tests showed that it was not possible to predict the bilateral benefit from a priori information based on headphone tests. At the end of the trial period 93% of the participants preferred a bilateral fitting.

Effects of reverberation and masker fluctuations on binaural unmasking of speech

In daily life, listeners use two ears to understand speech in situations which typically include reverberation and non-stationary noise. In headphone experiments, the binaural benefit for speech in noise is often expressed as the difference in speech reception threshold between diotic (N(0)S(0)) and dichotic (N(0)S(π)) conditions. This binaural advantage (BA), arising from the use of inter-aural phase differences, is about 5-6 dB in stationary noise, but may be lower in everyday conditions. In the current study, BA was measured in various combinations of noise and artificially created diotic reverberation, for normal-hearing and hearing-impaired listeners. Speech-intelligibility models were applied to quantify the combined effects. Results showed that in stationary noise, diotic reverberation did not affect BA. BA was reduced in conditions where the masker fluctuated. With additional reverberation, however, it was restored. Results for both normal-hearing and hearing-impaired listeners were accounted for by assuming that binaural unmasking is only effectively realized at low instantaneous speech-to-noise ratios (SNRs). The observed BA was related to the distribution of SNRs resulting from fluctuations, reverberation, and peripheral processing. It appears that masker fluctuations and reverberation, both relevant for everyday communication, interact in their effects on binaural unmasking and need to be considered together.

The Influence of Masker Type on the Binaural Intelligibility Level Difference

The Binaural Intelligibility Level Difference (BILD) was first described by Licklider (1948). It is a manifestation of binaural unmasking, the advantage of binaural over monaural hearing of a signal S against the background of a spatially separated noise N. In headphone experiments, often a design with a N0S0 presentation vs a N0Sπ presentation is used, in which the noise is presented homophasic and the signal either homophasic or antiphasic. The BILD is then defined as the difference in the speech reception threshold (SRT) in the N0S0 and N0Sπ presentation mode. Blauert (1997) provides an overview of experimental work on BMLD and BILD. Estimating the BILD requires SRT measurements in the N0S0 and N0Sπ presentation modes. Since the diotic N0S0 stimuli contain no binaural information, they can be considered as an estimation of monaural speech perception (Siegel and Colburn 1983). The BILD for a stationary masker is known to be about 4–7 dB (e.g. Blauert 1997; Johansson and Arlinger 2002). We are interested in the BILD for fluctuating maskers because of their relevance for daily life. Assessing speech intelligibility in the presence of a fluctuating masker in a N0Sπ condition, several components should be taken into account (see Fig. 1): point of departure is the diotic speech reception threshold (SRT) for stationary noise (Fig. 1a.). If temporal modulations are introduced there will be release of masking (masking release, MR), the SRT reduces (Fig. 1b.). A typical value is of this masking release is 10 dB. On the other hand, if an interaural phase shift is introduced in the speech-signal the SRT will be reduced because of binaural unmasking (Fig. 1c.). A typical value of this binaural unmasking is 5 dB. The question addressed is this chapter is whether there is an interaction between the diotic (“monaural”) release of masking and the binaural unmasking. So, can the reduction in SRT in the condition with modulated noise and interaural phase shifted speech be predicted by adding the values of masking release and binaural unmasking, i.e. 10 + 5 = 15 dB or is it different?

A process evaluation of implementing a vocational enablement protocol for employees with hearing difficulties in clinical practice

Abstract Objective: A multidisciplinary vocational rehabilitation programme, the Vocational Enablement Protocol (VEP) was developed to address the specific needs of employees with hearing difficulties. In the current study we evaluated the process of implementing the VEP in audiologic care among employees with hearing impairment. Design: In conjunction with a randomized controlled trial, we collected and analysed data on seven process parameters: recruitment, reach, fidelity, dose delivered, dose received and implemented, satisfaction, and perceived benefit. Study sample: Sixty-six employees with hearing impairment participated in the VEP. The multidisciplinary team providing the VEP comprised six professionals. Results: The professionals performed the VEP according to the protocol. Of the recommendations delivered by the professionals, 31% were perceived as implemented by the employees. Compliance rate was highest for hearing-aid uptake (51%). Both employees and professionals were highly satisfied with the VEP. Participants rated good perceived benefit from it. Conclusions: Our results indicate that the VEP could be a useful treatment for employees with hearing difficulties from a process evaluation perspective. Implementation research in the audiological setting should be encouraged in order to further provide insight into parameters facilitating or hindering successful implementation of an intervention and to improve its quality and efficacy.

The Addition of a Contralateral Microphone for Unilateral Cochlear Implant Users: Not an Alternative for Bilateral Cochlear Implantation

Objective This study aimed to investigate whether unilateral cochlear implant (CI) users benefit from the addition of a contralateral microphone (CI-CROS) for spatial speech recognition. Setting Tertiary referral otology and cochlear implant center. Methods The digits-in-noise test was used to measure speech in noise recognition abilities. Evaluations were made in 3 conditions: speech and noise presented from the front of the listener (S0N0) and with spatial separation of speech and noise (S90N-90 and S-90N90). The performance of CI patients using CI-CROS was compared with their unilateral CI condition (n = 10), normal-hearing subjects (n = 12), and bilateral CI users (n = 5). The presence and extent of several binaural phenomena (binaural summation, binaural squelch, and the better-ear effect) were evaluated. Results CI-CROS only provided a benefit in the listening situation wherein speech originates from the side of the CROS microphone; however, this benefit was repealed by disadvantages in other listening conditions. With CI-CROS, the hearing of patient is essentially monaural, albeit with bilateral input; therefore, patients were not able to benefit from the same binaural advantages as normal-hearing subjects and bilateral CI users. Moreover, patients using CI-CROS lost the ability to choose the optimal listening condition to perform as well as unilateral CI users. Conclusion We conclude that CI-CROS is not advisable for unilateral CI users. Bilateral cochlear implantation would be a better alternative for the rehabilitation of patients with unaidable hearing on the contralateral side.

The Effectiveness of a Vocational Enablement Protocol for Employees With Hearing Difficulties: Results of a Randomized Controlled Trial

The aim of this study was to evaluate the effectiveness of a vocational enablement protocol (VEP) on need for recovery (NFR) after work as compared with usual care for employees with hearing difficulties. In a randomized controlled trial design, 136 employees with hearing impairment were randomly assigned to either the VEP or the control group. VEP is a multidisciplinary program integrating audiological and occupational care for individuals experiencing difficulties in the workplace due to hearing loss. The primary outcome measure was NFR. Secondary outcome measures were communication strategy subscales (e.g., self-acceptance and maladaptive behavior), distress, and self-efficacy. Data were collected using questionnaires at baseline and at 3, 6, 9, and 12 months follow-up. No significant difference over the complete follow-up period was found between the intervention and control group for NFR. However, we observed a significant difference for one of the secondary outcomes after 12 months. “Self-acceptance” increased significantly in the VEP group, compared with the controls. The mean difference between the two groups was small, being only 0.24 (95% CI [0.04, 0.44]) on a scale of 1 to 5. The results do not support the use of VEP if the aim is to reduce NFR after work at 12 months follow-up. It may be that NFR does not adequately capture what is covered in the VEP. Although marginal, the effect on self-acceptance was significant. This is encouraging given that positive effects on self-acceptance have rarely been shown for audiological rehabilitation programs. Suggestions for further improvement of the VEP are discussed.

Morphosyntactic correctness of written language production in adults with moderate to severe congenital hearing loss

OBJECTIVE To examine whether moderate to severe congenital hearing loss (MSCHL) leads to persistent morphosyntactic problems in the written language production of adults, as it does in their spoken language production. DESIGN Samples of written language in Dutch were analysed for morphosyntactic correctness and syntactic complexity. STUDY SAMPLE 20 adults with MSCHL and 10 adults with normal hearing (NH). RESULTS Adults with MSCHL did not differ from adults with NH in the morphosyntactic correctness and syntactic complexity of their written utterances. Within the MSCHL group, the number of morphosyntactic errors in writing was related to the degree of hearing loss in childhood. CONCLUSIONS At the group level, MSCHL does not affect the morphosyntactic correctness of language produced in the written modality, in contrast to earlier observed effects on spoken language production. However, at the individual level, our data suggest that adults who acquired their language with more severe auditory limitations are more at risk of persistent problems with morphosyntax in written language production than adults with a lower degree of hearing loss in childhood.