Preliminary evaluation of a novel non-linear frequency compression scheme for use in children

Effects of Adaptive Non-linear Frequency Compression in Hearing Aids on Mandarin Speech and Sound-Quality Perception

Objective

This study was aimed at examining the effects of an adaptive non-linear frequency compression algorithm implemented in hearing aids (i.e., SoundRecover2, or SR2) at different parameter settings and auditory acclimatization on speech and sound-quality perception in native Mandarin-speaking adult listeners with sensorineural hearing loss.

Design

Data consisted of participants’ unaided and aided hearing thresholds, Mandarin consonant and vowel recognition in quiet, and sentence recognition in noise, as well as sound-quality ratings through five sessions in a 12-week period with three SR2 settings (i.e., SR2 off, SR2 default, and SR2 strong).

Study Sample

Twenty-nine native Mandarin-speaking adults aged 37–76 years old with symmetric sloping moderate-to-profound sensorineural hearing loss were recruited. They were all fitted bilaterally with Phonak Naida V90-SP BTE hearing aids with hard ear-molds.

Results

The participants demonstrated a significant improvement of aided hearing in detecting high frequency sounds at 8 kHz. For consonant recognition and overall sound-quality rating, the participants performed significantly better with the SR2 default setting than the other two settings. No significant differences were found in vowel and sentence recognition among the three SR2 settings. Test session was a significant factor that contributed to the participants’ performance in all speech and sound-quality perception tests. Specifically, the participants benefited from a longer duration of hearing aid use.

Conclusion

Findings from this study suggested possible perceptual benefit from the adaptive non-linear frequency compression algorithm for native Mandarin-speaking adults with moderate-to-profound hearing loss. Periods of acclimatization should be taken for better performance in novel technologies in hearing aids.

Effects of nonlinear frequency compression on Mandarin speech and sound-quality perception in hearing-aid users

Objective: The purpose of the present study was to examine the effects of NLFC fitting in hearing aids and auditory acclimatisation on speech perception and sound-quality rating in hearing-impaired, native Mandarin-speaking adult listeners.Design: Mandarin consonant, vowel and tone recognition were tested in quiet and sentence recognition in noise (speech-shaped noise at a +5 dB signal-to-noise ratio) with NLFC-on and NLFC-off. Sound-quality ratings were collected on a 0-10 scale at each test session. A generalised linear model and correlational analyses were performed.Study sample: Thirty native Mandarin-speaking adults with moderate-to-severe sensorineural hearing loss were recruited.Results: The hearing-impaired listeners showed significantly higher accuracy with NLFC-on than with NLFC-off for consonant and sentence recognition and the recognition performance improved with both NLFC-on and off as a function of increased length of use. The satisfaction score of sound-quality ratings for different types of sounds significantly increased with NLFC-on than with NLFC-off. The speech recognition results showed moderate to strong correlation with the unaided hearing thresholds.Conclusion: For native Mandarin-speaking listeners with hearing loss, the NLFC technology provided modest but significant improvement in Mandarin fricative and sentence recognition. Subjectively, the naturalness and overall preference of sound-quality satisfaction judgement also improved with NLFC.

Speech Perception and Sound-Quality Rating with an Adaptive Nonlinear Frequency Compression Algorithm in Mandarin-Speaking Hearing Aid Users

BACKGROUND

Mandarin Chinese has a rich repertoire of high-frequency speech sounds. This may pose a remarkable challenge to hearing-impaired listeners who speak Mandarin Chinese because of their high-frequency sloping hearing loss. An adaptive nonlinear frequency compression (adaptive NLFC) algorithm has been implemented in contemporary hearing aids to alleviate the problem.

PURPOSE

The present study examined the performance of speech perception and sound-quality rating in Mandarin-speaking hearing-impaired listeners using hearing aids fitted with adaptive NLFC (i.e., SoundRecover2 or SR2) at different parameter settings.

RESEARCH DESIGN

Hearing-impaired listeners' phoneme detection thresholds, speech reception thresholds, and sound-quality ratings were collected with various SR2 settings.

STUDY SAMPLE

The participants included 15 Mandarin-speaking adults aged 32 to 84 years old who had symmetric sloping severe-to-profound sensorineural hearing loss.

INTERVENTION

The participants were fitted bilaterally with Phonak Naida V90-SP hearing aids.

DATA COLLECTION AND ANALYSIS

The outcome measures included phoneme detection threshold using the Mandarin Phonak Phoneme Perception test, speech reception threshold using the Mandarin hearing in noise test (M-HINT), and sound-quality ratings on human speech in quiet and noise, bird chirps, and music in quiet. For each test, five experimental settings were applied and compared: SR2-off, SR2-weak, SR2-default, SR2-strong 1, and SR2-strong 2.

RESULTS

The results showed that listeners performed significantly better with SR2-strong 1 and SR2-strong 2 settings than with SR2-off or SR2-weak settings for speech reception threshold and phoneme detection threshold. However, no significant improvement was observed in sound-quality ratings among different settings.

CONCLUSIONS

These preliminary findings suggested that the adaptive NLFC algorithm provides perceptual benefit to Mandarin-speaking people with severe-to-profound hearing loss.

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.

The Use of Frequency Lowering Technology in the Treatment of Severe-to-Profound Hearing Loss: A Review of the Literature and Candidacy Considerations for Clinical Application

This article provides a review of the current literature on the topic of frequency lowering hearing aid technology specific to the treatment of severe and profound levels of hearing impairment in child and adult listeners. Factors to consider when assessing listener candidacy for frequency lowering technology are discussed. These include factors related to audiometric assessment, the listener, the type of hearing aid technology, and the verification and validation procedures that can assist in determining candidacy for frequency lowering technology. An individualized candidacy assessment including the use of real-ear verification measures and carefully chosen validation tools are recommended for listeners requiring greater audibility of high-frequency sounds, when compared with amplification via conventional hearing aid technology.

Effects of nonlinear frequency compression on the acoustic properties and recognition of speech sounds in Mandarin Chinese

The present study examined the change in spectral properties of Mandarin vowels and fricatives caused by nonlinear frequency compression (NLFC) used in hearing instruments and how these changes affect the perception of speech sounds in normal-hearing listeners. Speech materials, including a list of Mandarin monosyllables in the form of /dV/ (12 vowels) and /Ca/ (five fricatives), were recorded from 20 normal-hearing, native Mandarin-speaking adults (ten males and ten females). NLFC was based on Phonak SoundRecover algorithms. The speech materials were processed with six different NLFC parameter settings. Detailed acoustic analysis revealed that the high front vowel /i/ and certain compound vowels containing /i/ demonstrated positional deviation in certain processed conditions in comparison to the unprocessed condition. All five fricatives showed acoustic changes in spectral features in all processed conditions. Fourteen Mandarin-speaking, normal-hearing adult listeners performed phoneme recognition with the six NLFC processing conditions. When the cut-off frequency was set relatively low, recognition of /s/ was detrimentally affected, whereas none of the NLFC processing configurations affected the other phonemes. The discrepancy between the considerable acoustic changes and the negligible adverse effects on perceptual outcomes is partially accounted for by the phonology system and phonotactic constraints in Mandarin.

Is non-linear frequency compression amplification beneficial to adults and children with hearing loss? A systematic review

OBJECTIVE

To conduct a systematic review of the benefits of non-linear frequency compression (NLFC) in adults and children.

DESIGN

Ten databases were searched for studies comparing the effects of NLFC and conventional processing (CP) for the period January 2008 to September 2017.

STUDY SAMPLE

Twelve articles were included in this review: four adults and school-aged only, one pre-school only and three with both adults and school-aged children.

RESULTS

A two-stage process was implemented to grade the evidence. The individual studies were graded based on their study type (from 1 = highest quality of evidence to 5 = the lowest quality) and then sub-graded based on their quality ("a" for "good quality" or "b" for "lesser quality"). All studies were awarded 4a, except the single pre-school study, which was awarded 2a. The overall evidence for each population was graded based on the quality, quantity and consistency of the studies. The body of evidence was rated as very low for both adults and school-aged children, but high for pre-school children.

CONCLUSION

The low number (and quality) of studies means that evidence supporting the benefit from NLFC is inconclusive. Further high-quality RCTs are required to provide a conclusive answer to this question.