Wide Dynamic Range Compression Hearing Research Articles

EFFECT OF DIGITAL NOISE REDUCTION AND DIRECTIONALITY ALGORITHMS IN HEARING AIDS ON TEMPORAL ENVELOPE DISTORTION AND SPEECH RECOGNITION

Background Digital signal processing algorithms tend to alter temporal cues in the speech signal and yet individuals with hearing impairment rely strongly on these cues for speech perception. Hence, there is a need to assess the effect of these algorithms on temporal cues and speech perception. The present study aimed to quantify, in a wide dynamic range compression hearing aid, the individual and combined effects of digital noise reduction and directionality algorithms on temporal cues, syllable recognition, and sentence recognition. Temporal cues were quantified by the envelope difference index (EDI). Material and methods The study included 20 individuals (in the age range of 21 to 44 years) with mild to moderate sensorineural hearing loss. Sentence recognition, syllable recognition, and EDI were obtained at different levels in four different aided conditions – digital noise reduction algorithm only, directionality only, both digital noise reduction and directionality on, and both algorithms off. Sentences were presented in noise at +5 dB signal-to-noise ratio from 180° azimuth. Results Compared to independent activation of the algorithms, the combined algorithms significantly improved speech recognition scores at all presentation levels. The temporal changes induced by the algorithms were only mild, even though EDI was the highest when all the algorithms and the directional microphone were activated. Conclusions The noise reduction algorithms and compression induce temporal changes; however speech recognition improved when the algorithms were activated, presumably due to countervailing psychophysical factors.

Cortical Evoked Potentials and Hearing Aids in Individuals with Auditory Dys-Synchrony.

The purpose of the present study was to investigate the relationship between cortical processing of speech and benefit from hearing aids in individuals with auditory dys-synchrony. Data were collected from 38 individuals with auditory dys-synchrony. Participants were selected based on hearing thresholds, middle ear reflexes, otoacoustic emissions, and auditory brain stem responses. Cortical-evoked potentials were recorded for click and speech. Participants with auditory dys-synchrony were fitted with bilateral multichannel wide dynamic range compression hearing aids. Aided and unaided speech identification scores for 40 words were obtained for each participant. Hierarchical cluster analysis using Ward's method clearly showed four subgroups of participants with auditory dys-synchrony based on the hearing aid benefit score (aided minus unaided speech identification score). The difference in the mean aided and unaided speech identification scores was significantly different in participants with auditory dys-synchrony. However, the mean unaided speech identification scores were not significantly different between the four subgroups. The N2 amplitude and P1 latency of the speech-evoked cortical potentials were significantly different between the four subgroups formed based on hearing aid benefit scores. The results indicated that subgroups of individuals with auditory dys-synchrony who benefit from hearing aids exist. Individuals who benefitted from hearing aids showed decreased N2 amplitudes compared with those who did not. N2 amplitude is associated with greater suppression of background noise while processing speech.

Spectral Tilt Change in Stop Consonant Perception by Listeners With Hearing Impairment

To evaluate how perceptual importance of spectral tilt is altered when formant information is degraded by sensorineural hearing loss. Eighteen listeners with mild to moderate hearing impairment (HI listeners) and 20-23 listeners with normal hearing (NH listeners) identified synthesized stimuli that varied in second formant (F(2)) frequency and spectral tilt. Experiments 1 and 2 examined utterance-initial stops (/ba/ and /da/), and Experiments 3 and 4 examined medial stops (/aba/ and /ada/). Spectral tilt was manipulated at either consonant onset (Experiments 1 and 3), vowels (Experiments 2 and 4), or both (Experiment 5). Regression analyses revealed that HI listeners weighted F(2) substantially less than NH listeners. There was no difference in absolute tilt weights between groups. However, HI listeners emphasized tilt as much as F(2) for medial stops. NH listeners weighted tilt primarily when F(2) was ambiguous, whereas HI listeners weighted tilt significantly more than NH listeners on unambiguous F(2) endpoints. Attenuating changes in spectral tilt can be as deleterious as taking away F(2) information for HI listeners. Recordings through a wide dynamic range compression hearing aid show compromised changes in spectral tilt, compressed in range by up to 50%.

Personal Amplification for School-Age Children with Auditory Processing Disorders

Children with auditory processing disorders (APD) are described to have a signal-to-noise ratio (SNR) difficulty. Frequency-modulated (FM) systems have been reported to improve this situation. Yet the use of personal amplification that may be more portable has not been attempted. To determine whether personal amplification would result in improvement in speech-in-noise performances (attentiveness and speech recognition) and daily functioning in children with diagnosed APD. In addition, the desired hearing aid features (such as required gain, directional microphone and noise reduction, and open-ear fitting) are examined. A single-blind, longitudinal descriptive study in which subjects served as their own control in various hearing aid conditions. Fourteen normal hearing children who had a diagnosis of APD and who were between the ages of 7 and 11 participated. All subjects wore bilateral, mild-gain, behind-the-ear, wide dynamic range compression hearing aids fitted in an open-ear mode. Gain on the hearing aids was adjusted to provide approximately 10 dB of insertion gain for conversational input. Directional microphone and noise reduction were used on the hearing aids. Subjects wore the hearing aids home and were encouraged to use them as much as possible in their daily environments (school, home, and social activities). Subjects were seen four times: an initial visit where hearing aids were fitted, then visits at 2 weeks, 3 months, and 6 months after the initial fitting. The majority of the testing was completed during these final three visits. The children were evaluated on the Northwestern University word-list (NU-6) and the Auditory Continuous Performance Test (ACPT) in noise at most visits. The hearing aids were evaluated in the omnidirectional microphone mode only, omnidirectional microphone with noise reduction (NR) mode, and directional microphone with NR mode. The children's parents and teachers were asked to complete the Children's Auditory Processing Performance Scale (CHAPS) questionnaire both before and at the end of the study. The results showed that the use of hearing aids in the omnidirectional microphone mode alone did not improve speech identification in noise over the unaided condition. However, the inclusion of the NR algorithm and directional microphones improved speech understanding in noise. Amplification reduced the number of errors on the ACPT and improved several areas on the CHAPS; however, the results were not statistically significant. The use of mild-gain, open-ear fitting hearing aids with a directional microphone and noise reduction algorithm may be attempted on some children with APD on a trial basis.

The Objective and Subjective Evaluation of Low-Frequency Expansion in Wide Dynamic Range Compression Hearing Instruments

The effects of low-frequency expansion on the objective and subjective evaluation of four channel in-the-ear hearing instruments was investigated. Three expansion settings were programmed in each device: expansion off, expansion restricted to channel one, and expansion restricted to channels one and two. Objective evaluations were conducted in quiet (Connected Speech Test) and in noise (Hearing in Noise Test) with speech levels fixed at 40 dB SPL. Subjectively, each participant rated expansion satisfaction in quiet and listening to low-level speech in a sound-treated room then indicated the expansion condition preferred overall. Listeners performed significantly better in quiet and in noise for the Off and Channel 1 conditions than the Channels 1 and 2 condition; however, performance was similar between the Off and Channel 1 conditions. Expansion effects on listener satisfaction ratings depended on the listening environment. Overall, listeners preferred expansion in Channel 1 to expansion in Channels 1 and 2; however, preference was not significantly different between the Channel 1 and Off conditions. Results indicate restricting expansion to 1000 Hz overcomes speech-recognition deficits observed with expansion active across a broader spectrum without significantly reducing subjective benefit or preference.

Current Practices in Pediatric Amplification and Early Intervention

No AccessPerspectives on Hearing and Hearing Disorders in ChildhoodArticle1 Mar 2007Current Practices in Pediatric Amplification and Early Intervention Kristina Rigsby, Tamala S. Bradham, William Dickinson and H. Gustav Mueller Kristina Rigsby Vanderbilt Bill Wilkerson Center, National Center for Childhood Deafness and Family CommunicationNashville, TN Google Scholar More articles by this author , Tamala S. Bradham Vanderbilt Bill Wilkerson Center, National Center for Childhood Deafness and Family CommunicationNashville, TN Google Scholar More articles by this author , William Dickinson Vanderbilt Bill Wilkerson Center, National Center for Childhood Deafness and Family CommunicationNashville, TN Google Scholar More articles by this author and H. Gustav Mueller Vanderbilt Bill Wilkerson Center, National Center for Childhood Deafness and Family CommunicationNashville, TN Google Scholar More articles by this author https://doi.org/10.1044/hhdc17.1.3 SectionsAboutFull TextPDF ToolsAdd to favoritesDownload CitationTrack Citations ShareFacebookTwitterLinked In References American Academy of Audiology Task Force Members. (2003). Pediatric Amplification Protocol.Retrieved June15, 2006, from http://audiology.org/publications/ documents/positions/pedrehab Google Scholar Culpepper, B., & Martin, P. (2005) Specialty recognition for pediatric audiology [presentation at the 2005 EHDI annual conference].Retrieved June15, 2006, from www.infanthearing.org/meeting/edhi2005 Google Scholar Harrison, M.,Dannhardy, M., & Roush, J., (1996). Families’ perceptions of early interventions services for children with hearing loss..Language, Speech, and Hearing Services in Schools, 27,203–214. Google Scholar Hedley-Williams, A.,Tharpe, A. M., & Bess, F. (1996). Fitting hearing aids in children: A survey of practice procedures. In.F. H. BessJ. S. Gravel & A. M. Tharpe (Eds.), Amplification for children with auditory deficits.: Nashville, TN: Bill Wilker-son Center Press. Google Scholar Jenstad, L. M.,Pumford, J.,Seewald, R. C., & Corneisse, L. E. (2000). Comparison of linear gain and wide dynamic range compressions hearing aid circuits: Aided speech perception measures..Earand Hearing, 21, 32–44. Google Scholar Jenstad, L. M.,Seewald, R. C.,Cornelisse, L. E., & Shantz, J., (1999). Comparison of linear gain and wide dynamic range compression hearing aid circuits: Aided speech perception measures..Ear and Hearing, 20, 117–126. Google Scholar Luterman, D., & Kurtzer-White, E. (1999). Identifying hearing loss: Parents’ needs..American Journal of Audiology, 8, 13–18. LinkGoogle Scholar Marriage, J.,Moore, B.,Stone, M., & Bear, T. (2005). Effects of three amplification strategies on speech perception by children with severe and profound hearing loss..Ear and Hearing, 26, 35–47. Google Scholar Marriage, J. E., & Moore, B. C. J. (2003). New speech tests reveal benefit of wide-dynamic-range, fast acting compression for consonant discrimination in children with moderate to severe hearing loss..Inter-nationalJournalof Audiology, 42, 418–425. Google Scholar Pediatric Working Group. (1996). Amplification for infants and children with hearing loss..American Journal of Audiology, 5, 53–68. Google Scholar Sjoblad, S.,Harrison, M.,Roush, J., & McWilliam, R. A. (2001). Parents’ reactions and recommendations after diagnosis and hearing aid fitting..American Journal of Audiology, 10,1–8. Google Scholar Smriga, D. J. (2000). Three digital signal processing schemes that can influence signal quality in noise..Seminars in Hearing, 21, 123–126. Google Scholar Yoshinaga-Itano, C.,Sedey, A.,Coulter, D., & Mehl, A. (1998). Language of early- and later-identified children with hearing loss..Pediatrics, 102, 1161–1171. Google Scholar Additional Resources FiguresReferencesRelatedDetailsCited ByJournal of Speech, Language, and Hearing Research54:4 (1224-1239)1 Aug 2011Children’s Performance in Complex Listening Conditions: Effects of Hearing Loss and Digital Noise ReductionAndrea PittmanPerspectives on School-Based Issues11:4 (126-132)1 Dec 2010Speech and Language of Children Using Hearing Aids With Adaptive Directional and Noise Reduction FeaturesJane Auriemmo and Patti Stenger Volume 17Issue 1March 2007Pages: 3-7 Get Permissions Add to your Mendeley library History Published in issue: Mar 1, 2007 Metrics Topicsasha-topicsleader-topicsasha-article-typesasha-sigsCopyright & Permissions© 2007 American Speech-Language-Hearing AssociationPDF DownloadLoading ...

The Objective and Subjective Evaluation of Multichannel Expansion in Wide Dynamic Range Compression Hearing Instruments

The effects of multichannel expansion on the objective and subjective evaluation of 20 listeners fitted binaurally with 4-channel, digital in-the-ear hearing instruments were investigated. Objective evaluations were conducted in quiet using the Connected Speech Test (CST) and in noise using the Hearing in Noise Test (HINT) at 40, 50, and 60 dB SPL. Subjective evaluations were conducted by having each participant (a) rate their satisfaction regarding the amount of noise reduction they perceived daily and (b) indicate which expansion condition they preferred overall after a 2-week trial. Three expansion settings were programmed into the hearing aids: 4-channel expansion, expansion restricted to Channels 1 and 2 only, and expansion off. Listeners performed significantly better in quiet (CST) and in noise (HINT) for the off condition than for either multichannel condition; however, restricting expansion to Channels 1 and 2 improved objective performance in quiet and in noise relative to the 4-channel condition. Conversely, satisfaction ratings were significantly greater for both multichannel conditions than for the off condition; however, satisfaction ratings were similar for the restricted and the 4-channel conditions. Overall, listeners preferred any form of multichannel expansion to no expansion; however, overall preference was similar for the restricted and the 4-channel conditions. Hearing instrument users prefer the use of multichannel expansion despite the fact multichannel expansion may significantly reduce the recognition of low-level speech in quiet and in noise. Although restricting expansion to Channels 1 and 2 (i.e., 2000 Hz and below) maintained subjective benefit for wide dynamic range compression hearing instrument users, the recognition of low-level speech was not completely preserved.

Audibility and Speech Perception of Children Using Wide Dynamic Range Compression Hearing Aids

This study examined the relation of audibility for frequency-specific sounds and the Speech Intelligibility Index (SII) to speech perception abilities of children with sensorineural hearing loss using digital signal-processing hearing aids with wide dynamic range compression. Twenty-six children age 5-15 years with pure-tone averages (0.5, 1.0, and 2.0 kHz) from 60-98 dB HL participated. Three subgroups were created based on the compression characteristics of each hearing aid. Minimum audibility was determined using aided thresholds for frequency-modulated tones and the SII calculated at 55 and 70 dB SPL using the simulated real-ear output of the hearing aid. The Lexical Neighborhood Test (LNT; K. I. Kirk, D. B. Pisoni, & M. J. Osberger, 1995) was presented at 50 and 70 dB SPL. LNT scores at 70 dB SPL were significantly higher than at 50 dB SPL. Average aided thresholds at 0.5, 1.0, and 2.0 kHz were negatively correlated with LNT scores at 50 dB SPL, and SIIs at 55 and 70 dB SPL were positively correlated with LNT scores at 50 and 70 dB SPL. Results support using aided thresholds and speech test scores at soft to loud levels as part of the amplification fitting process.

The subjective evaluation of the expansion time constant in single-channel wide dynamic range compression hearing instruments

The present study investigated the subjective evaluation of expansion time constants in single-channel wide dynamic range compression (WDRC) hearing instruments. Thirty participants utilized binaural WDRC hearing instruments for a two-week trial. Subjective evaluations were conducted by having each participant rate their satisfaction with the expansion time constant on a daily basis and by having each participant indicate their preferred expansion time constant following the completion of the two-week trial. Each change in expansion time constant significantly affected listener satisfaction; however, all time constants resulted in satisfactory performance. Of the users expressing a preference, 75% preferred fast-acting over slow-acting expansion. These findings suggest that dynamic expansion parameters play an important role in determining the effectiveness of the feature for a given listener.

The effects of compression ratio, signal-to-noise ratio, and level on speech recognition in normal-hearing listeners.

Previous research has demonstrated reduced speech recognition when speech is presented at higher-than-normal levels (e.g., above conversational speech levels), particularly in the presence of speech-shaped background noise. Persons with hearing loss frequently listen to speech-in-noise at these levels through hearing aids, which incorporate multiple-channel, wide dynamic range compression. This study examined the interactive effects of signal-to-noise ratio (SNR), speech presentation level, and compression ratio on consonant recognition in noise. Nine subjects with normal hearing identified CV and VC nonsense syllables in a speech-shaped noise at two SNRs (0 and +6 dB), three presentation levels (65, 80, and 95 dB SPL) and four compression ratios (1:1, 2:1, 4:1, and 6:1). Stimuli were processed through a simulated three-channel, fast-acting, wide dynamic range compression hearing aid. Consonant recognition performance decreased as compression ratio increased and presentation level increased. Interaction effects were noted between SNR and compression ratio, as well as between presentation level and compression ratio. Performance decrements due to increases in compression ratio were larger at the better (+6 dB) SNR and at the lowest (65 dB SPL) presentation level. At higher levels (95 dB SPL), such as those experienced by persons with hearing loss, increasing compression ratio did not significantly affect speech intelligibility.

Comparison of Linear Gain and Wide Dynamic Range Compression Hearing Aid Circuits II: Aided Loudness Measures

The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit fitted using the DSL method for increased dynamic range and normalized loudness growth. Ten adolescents and young adults with moderate to severe sensorineural hearing loss were fitted monaurally with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Threshold, upper limit of comfort and loudness growth were measured in the unaided, linear gain and WDRC conditions for warble tones, environmental sounds and speech. Twelve adult listeners with normal hearing also were tested monaurally in the unaided condition to provide normative data for comparison purposes. The WDRC hearing aid provided a greater input dynamic range than the linear circuit for all stimuli. The dynamic range was normalized for more subjects with the WDRC than the linear hearing aid. In addition, exponential loudness growth functions fitted to the loudness growth data showed that, on average, loudness growth was more normalized with the WDRC hearing aid fitted to DSL[i/o] targets than the linear hearing aid fitted to DSL[i/o] targets. WDRC processing, fitted using the DSL[i/o] method, has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides an audible, comfortable and tolerable amplified signal across a wider range of inputs than linear gain processing, without the need for volume control adjustments.

Fitting Wide Dynamic Range Compression Hearing Aids

Fitting Wide Dynamic Range Compression Hearing Aids

A prescription for a nonlinear hearing aid using speech intelligibility and loudness models

A method for prescribing a nonlinear hearing aid using a simplified loudness model and the speech intelligibility index (SII) model [ANSI draft (1993)] is described. The specific loudness of a signal is calculated as a linear function of the sound-pressure level bounded between threshold and UCL. An integrated-SII model is constructed by computing the weighted sum of the SII values across several listening conditions [Hou and Thornton, Ear Hear. 15, 105–112 (1994)]. The fundamental goal of the method is to adjust the hearing aid parameters so as to maximize the integrated SII. The specific loudness of the aided speech and noise for a hearing-impaired subject is constrained so as not to exceed the specific loudness of the unaided signals for normal-hearing listeners in each listening condition. The method is applied to a database of patients who wear multiband wide dynamic range compression hearing devices. Resulting hearing aid program parameters are compared with the patients’ existing programs.