Acta Oto-Laryngologica
ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Improved speech reception and sound quality with the DUET2 audio processor for electric acoustic stimulation Andrea Kleine Punte, Griet Mertens, Ellen Cochet, Marc De Bodt & Paul Van de Heyning To cite this article: Andrea Kleine Punte, Griet Mertens, Ellen Cochet, Marc De Bodt & Paul Van de Heyning (2015) Improved speech reception and sound quality with the DUET2 audio processor for electric acoustic stimulation, Acta Oto-Laryngologica, 135:10, 1022-1029, DOI: 10.3109/00016489.2015.1050605 To link to this article: http://dx.doi.org/10.3109/00016489.2015.1050605
Published online: 13 Jun 2015.
Submit your article to this journal
Article views: 26
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ioto20 Download by: [Chelsea & Westminster NHS Trust Dept of Urology]
Date: 04 October 2015, At: 17:10
Acta Oto-Laryngologica. 2015; 135: 1022–1029
ORIGINAL ARTICLE
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
Improved speech reception and sound quality with the DUET2 audio processor for electric acoustic stimulation
ANDREA KLEINE PUNTE, GRIET MERTENS, ELLEN COCHET, MARC DE BODT & PAUL VAN DE HEYNING Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University Hospital, University of Antwerp, Belgium
Abstract Conclusion: The results show that the DUET2 offers users speech perception that is equivalent to or better than the DUET. Moreover, the DUET2 offers subjective benefits above those provided by the DUET. Background: The DUET is a combination of hearing aid and CI in one device for electric acoustic stimulation. Since its introduction: a second generation, the DUET2, has been developed. This study aimed to investigate the benefits of the DUET2 compared to the DUET. Methods: Speech reception was determined in quiet and in noise. The sound quality of speech and music was rated using a visual analogue scale. Test intervals were at upgrade and at 3 and 6 months after upgrade. Results: Speech reception in quiet and in noise was significantly better than with the DUET after 6 months. For sentence reception in quiet, the SRT with the DUET2 did not change significantly between test intervals. Sentence reception in noise with the DUET2 improved significantly between 3 and 6 months and upgrade and 6 months. After 6 months, speech reception in quiet and in noise with the DUET2 was significantly better than with the DUET. Subjects rated the sound quality of speech and of music with the DUET2 significantly better than with the DUET.
Keywords: Speech processor, electric acoustic stimulation, sound quality, cochlear implants, subjective benefit, auditory outcome measures
Introduction Patients with residual hearing in the low frequencies and severe-to-profound hearing loss in the higher frequencies can benefit from a combination of electrical and acoustical hearing in the same ear [1–4]. While hearing aids (HAs) are particularly effective at providing amplification of low frequencies, the compensation of severe hearing loss in the high frequency range (> 1000 Hz; > 70 dB hearing loss) is often insufficient [5]. Thus, to provide auditory stimulation over a complete frequency range (up to 6000 Hz), a HA is used in combination with electric stimulation, in the form of a cochlear implant (CI) [6]. The combination of both devices in one ear is called electric acoustic stimulation (EAS). The use of
multiple devices simultaneously to deliver electrical and acoustical stimulation proves cumbersome because multiple devices require different types of batteries, with different battery life spans, and inthe-ear HAs provide inadequate amplification to patients with moderate hearing loss at low frequency thresholds (< 500 Hz) [7]. The DUET audio processor was, therefore, developed in order to offer a combination of HA and CI in one device [7]. The HA of the DUET was specially designed to achieve acoustic amplification in the low frequencies between 125–1500 Hz, while the mid-to-high frequencies are transmitted electrically via the CI with the same audio processor. A second generation of this device called the DUET2 has subsequently been developed. The
Correspondence: Paul Van de Heyning, Antwerp University Hospital, Department of Otolaryngology and Head and Neck Surgery, Wilrijkstraat 10, 2650 Edegem, Belgium. Tel: +0032-38214059. Fax: +0032-38250536. E-mail: [email protected]
(Received 8 April 2015; accepted 3 May 2015) ISSN 0001-6489 print/ISSN 1651-2251 online 2015 Informa Healthcare DOI: 10.3109/00016489.2015.1050605
Speech reception and sound quality with DUET2 for EAS
1023
Table 1. Demographic information. Subject Gender Etiology of Ear Contralateral ID Deafness Implanted Amplification
Electrode Implant Type
Age (years)
Duration of DUET Experience (months)
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
First Upgrade Implantation 1a*
Male
Ototoxicity Right
Bilateral EAS
Medium
1b*
Male
Ototoxicity Left
Bilateral EAS
FLEXSOFT PULSAR
2
Male
Trauma
Left
Hearing Aid
3
Male
Hereditary
Left
No
4
Female
Ototoxicity Left
5
Male
Hereditary
Left
COMBI40+ 47.7
53.2
43,6
47.7
53.2
43,5
Medium
COMBI40+ 60.8
66.1
43,9
Medium
COMBI40+ 69.0
75.2
43,6
No
Medium
COMBI40+ 50.3
54.2
43,3
Hearing Aid
FLEX24
PULSAR
58.3
60.9
27,3
24
6
Female
Hereditary
Right
Hearing Aid
FLEX
PULSAR
71.5
73.6
22,7
7
Female
Hereditary
Right
Hearing Aid
FLEX24
PULSAR
64.6
68.1
38,6
SONATA
21.8
23.0
12,9
8
Male
Ototoxicity Right
No
24
FLEX
*Bilaterally upgraded subject. Each ear was treated as an individual case.
DUET2 is different in design to the DUET; it has improved signal processing capabilities, includes a remote control and a battery alert function [8,9]. With the DUET2 audio processor, the latest speech coding strategies offered by the Maestro fitting software can be implemented. The output of the HA is also greater than with the first generation DUET audio processor (DUET 40dB max vs DUET2 43 dB max). Furthermore, the DUET2 uses an improved microphone compared to the DUET. The speech coding strategies currently available for the DUET are: High Definition Continuous Interleaved Sampling (HDCIS), Fine Structure Processing (FSP), Fine Structure4 (FS4), and FS4p (parallel signal processing) (as cited in Arnolder et al. [10] and Riss et al. [11]). This study aimed to investigate the benefits of the DUET2 compared to the DUET speech processor in terms of speech perception, sound quality of speech and music, and overall user satisfaction.
Materials and methods Subjects Eight Dutch speaking patients were included in this study (five male and three female). The mean age at first implantation was 55.5 ± 15.9 years. The mean age at upgrade was 59.3 ± 16.7 years. For further demographic data see Table I. One subject used bilateral EAS; seven subjects were unilateral EAS users. All subjects were experienced DUET users. The average duration of DUET experience before upgrade was 2.9 ± 1.0 year.
Methods All subjects were upgraded from the DUET to the DUET2 audio processor by simply transferring the individual subject’s DUET program to the DUET2. The bilateral EAS user was bilaterally upgraded, both ears were tested independently with the processor taken off and the contralateral ear plugged. Both processors were fitted according to the instructions in the MAESTRO software manual, and according to the DUET System Data Sheet. The ‘electrical part’ of the EAS was set using the reduced overlapping frequency range, where the programmed CI frequency range starts at the cross-over frequency of the audiogram (defined as that frequency where the audiogram passes the 65 dB HL point). Subjects used the CIS+ speech coding strategy with the DUET and the HDCIS speech coding strategy with the DUET2. For the ‘acoustical part’ of the DUET and the DUET2, the half-gain rule was used: the threshold of a given frequency was divided in half to obtain the predicted gain. Speech reception thresholds (SRT) in quiet and in noise were assessed using the Leuven Intelligibility Sentence Test (LIST) [12] in an adaptive procedure. In quiet and in noise the initial speech level was 65 dB SPL. For the testing in noise condition, speechweighted stationary noise, based on the long-term average speech spectrum of the sentences, was used with the noise level fixed at 65 dB SPL. The level of the sentences varied in steps of 2 dB adaptively in a one-down-, one-up-procedure according to the subject’s response. The SRT was ascertained on the basis of the level of the last six sentences of one list, including an imaginary 11th sentence.
1024
A. Kleine Punte et al.
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
A
B
Figure 1. Mean outcome of the Leuven Intelligibility Sentence Test (adaptive auditory speech test) in (A) quiet (dB HL) and (B) noise (dB SNR), using the DUET or the DUET2 audio processor (n = 9). Error bars represent standard deviation.
Monosyllable word recognition testing was performed using a fixed procedure in quiet with a speech level of 65 dB SPL and in noise at +5 dB signal-tonoise ratio (SNR). The sound quality of speech and music was rated (0–100) using a visual analog scale (VAS). The sound files used were taken from a Flemish listening book and instrumental versions of popular songs. Both sound files were presented in free field at a comfortable level, 1 m in front of the subject. The test intervals used were at the time of upgrade to the DUET2, 3 months after upgrade to the DUET2, and 6 months after upgrade. At upgrade, subjects were tested with the DUET and the DUET2 audio processor. At the 3-month test interval, subjects were tested with the DUET2 only. Ethics approval Local ethics committee approval was obtained. All subjects gave written informed consent prior to participation in this study.
Statistical analyses SRT levels (mean ± SD) for LIST sentence test results in quiet (dB HL) and in noise (dB SNR) for the different audio processors and test intervals are presented. Percentage values for monosyllable speech recognition in quiet and in noise and the average score on the VAS are shown for the two audio processors and the intervals tested (mean ± SD). Paired sample t-tests were used to analyze differences between the two audio processors and between the test intervals. Repeated measure (RM) ANOVA was performed to test the effect of time with the DUET2. If performance was stable at the upgrade interval, the DUET results at upgrade were compared to the DUET2 results after 6 months of listening experience, using the paired sample t-test. The normality of the distribution was confirmed using the Kolmogorov-Smirnov test. Missing data were not replaced but treated as missing values. A p-value < 0.05 was determined as statistically significant. IBM SPSS Statistics 19.0 software (IBM,
Speech reception and sound quality with DUET2 for EAS
1025
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
A
B
Figure 2. Mean percentage correct monosyllable speech recognition in (A) quiet; and (B) noise, using the DUET or the DUET2 audio processor (n = 9). Error bars represent standard deviation.
Armonik, NY) was used for the statistical analyses. Graphs were created in Microsoft Office Excel 2010 (http//www.microsoft.com). Results Adaptive speech perception Figure 1A shows the mean SRT in quiet determined using the LIST (dB HL). The SRT with the DUET2 at upgrade in quiet (32.8 ± 13.4 dB) did not change significantly (p = 0.201) compared to the SRT in quiet with the DUET (29.9 ± 9.4 dB). After 3 months, the SRT with the DUET2 in quiet was 32.6 ± 8.3 dB. After 6 months, the SRT with the DUET in quiet was 34.9 ± 10.3 dB. The SRT with the DUET2 in quiet after 6 months (30.7 ± 8.5 dB) was significantly better than with the DUET at 6 months (p = 0.035). Between upgrade and 6 months, the SRT in quiet worsened significantly (p = 0.035) with the DUET. In contrast, DUET2 results improved slightly, but not significantly, over time (F(2;16) = 0.474; p = 0.631).
No significant difference was found between the DUET at upgrade and DUET2 after 6 months of listening experience (p = 0.539). Figure 1B shows the mean SRT in noise determined using the LIST (dB SNR). There was no significant difference (p = 1.000) in the SRT in noise between the two audio processors at upgrade (DUET = 7.0 ± 4.8 dB; DUET2 = 7.0 ± 5 dB). After 3 months, the SRT in noise with the DUET2 was 6.7 ± 3.9 dB. After 6 months, the SRT with the DUET in noise was 9.7 ± 3.9 dB. The SRT with the DUET2 in noise after 6 months (3.3 ± 2.7 dB) was significantly better than with the DUET at 6 months (p = 0.001). Between upgrade and 6 months, the SRT in noise was not significantly different with the DUET (p = 0.104). In contrast, the SRT in noise with the DUET2 changed significantly over time (F(2;16) = 6.041; p = 0.011). Between upgrade and 3 months, the difference was not significant (p = 0.813). However, between 3–6 months, the SRT in noise with the DUET2 improved significantly (p = 0.002). The SRT in noise with the DUET2 after 6 months of listening
1026
A. Kleine Punte et al.
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
A
B
Figure 3. Mean level of satisfaction with (A) speech; and (B) music using the DUET or the DUET2 audio processor (n = 9). Error bars represent standard deviation.
experience was significantly better than with the DUET at upgrade (p = 0.005). Monosyllable word recognition Figure 2A shows the monosyllable word recognition in quiet (percentage correct). The monosyllable word recognition at upgrade, with the DUET in quiet, was 48.5 ± 19.4%. The monosyllable word recognition at upgrade, with the DUET2 in quiet (40.9 ± 21.1%), did not change significantly compared with the monosyllable word recognition in quiet with the DUET. After 3 months, the monosyllable word recognition with the DUET2 in quiet was 52.0 ± 20.0%. After 6 months, the monosyllable word recognition with the DUET in quiet was 37.4 ± 16.8%. The monosyllable word recognition with the DUET2 in quiet after 6 months (60.6 ± 20.5%) was significantly greater than with the DUET after 6 months (p = 0.028). Between upgrade and 6 months, the monosyllable word recognition in quiet with the DUET did not change significantly (p = 0.186). With the DUET2, however, there was a significant effect over time (F
(2;16) = 5.819; p = 0.013). The monosyllable word recognition in quiet improved significantly with the DUET2 between upgrade and 3 months (p = 0.033). The improvement in monosyllable word recognition in quiet with the DUET2 was not significantly different between 3- and 6-months (p = 0.135). The monosyllable word recognition in quiet, with the DUET2, after 6 months of listening experience, was significantly better than with the DUET at upgrade (p = 0.018). Figure 2B shows the mean percentage monosyllable word recognition in noise (+5 dB SNR). The monosyllable word recognition at upgrade, with the DUET in noise, was 33.3 ± 24.8%. The monosyllable word recognition at upgrade, with the DUET2 in noise (31.8 ± 20.5%), did not change significantly compared with the monosyllable word recognition at upgrade in noise with the DUET (p = 0.806). After 3 months, the monosyllable word recognition with the DUET2 in noise was 40.4 ± 22.3%. After 6 months, the monosyllable word recognition with the DUET in noise was 27.3 ± 13.8%. Monosyllable word recognition with the DUET2 in noise, after 6 months
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
Speech reception and sound quality with DUET2 for EAS (44.4 ± 21.4%), was significantly greater than with the DUET (p = 0.031). Between upgrade and 6 months, the monosyllable word recognition in noise with the DUET did not change significantly (p = 0.428). Similarly, between the time of upgrade and 6 months, word recognition in noise did not change significantly with the DUET2 (F(2;16) = 2.535; p = 0.111). The monosyllable word recognition in noise with the DUET2, after 6 months of listening experience, was significantly better than with the DUET at upgrade (p = 0.032). Sound quality of speech and music The mean level of satisfaction with the sound quality of speech, determined using a VAS, is shown in Figure 3A. At upgrade, the level of satisfaction with the sound quality of speech with the DUET was not significantly different to the DUET2 (p = 0.380). However, after 6 months, the level of satisfaction with the sound quality of speech with the DUET2 was rated significantly better than with the DUET (p = 0.028). The level of satisfaction with the sound quality of speech with the DUET was not significantly different between upgrade and 6 months (p = 0.923). Similarly, the level of satisfaction with the sound quality of speech with the DUET2 did not improve significantly over time (F(2;16) = 1.072; p = 0.366). The level of satisfaction with the sound quality of speech with the DUET2 after 6 months was significantly better than with the DUET at upgrade (p = 0.025). The mean level of satisfaction with the sound quality of music, determined using a VAS, is shown in Figure 3B. At upgrade, the level of satisfaction with the sound quality of music with the DUET was not significantly different to the DUET2 (p = 0.311). After 6 months, the level of satisfaction with the sound quality of music with the DUET2 was rated significantly better than with the DUET (p = 0.008). The level of satisfaction with the sound quality of music with the DUET was not significantly different between upgrade and 6 months (p = 0.838). The DUET2 results showed a tendency towards a significant effect of time (F(2;16) = 3.086; p = 0.074). This trend towards a significant improvement with the DUET2 in the level of satisfaction with the sound quality of music, was observed between 3 and 6 months (p = 0.051). The sound quality of music with the DUET2 after 6 months was significantly better than with the DUET at upgrade (p = 0.036). Subjects reported a more natural sound quality with the DUET2 compared to the DUET, and ease of listening also improved with the DUET2. Overall, subjects preferred the DUET2 compared to the DUET. After the trial period, subjects were offered
1027
their original audio processor back, but all subjects declined and continued using the DUET2 audio processor. Discussion The results of the present study show that the DUET2 offers users speech perception and recognition that is equivalent to, or better than, the DUET. Moreover, the DUET2 offers subjective benefits above those provided by the DUET, such as improved sound quality of speech and improved sound quality of music. Furthermore, the data show that it can take time for adult CI users to become accustomed to their new audio processor. Lorens et al. [13] suggests that the relatively stable results found over time with the DUET indicated that the learning with the DUET was complete before upgrade to the DUET2. Only patients with a minimum of 12 months experience were included in the Lorens et al. study. Similarly, in the present study, subjects had over 12 months of experience with the DUET2 (2.9 ± 1.0 year). The SRT in quiet with the DUET deteriorated significantly between upgrade and 6 months. While the SRT results in noise with the DUET did not change significantly between upgrade and 6 months, the SRT showed a trend towards a decrease. This result suggests that learning with the DUET was complete before upgrade. However, not only had subjects finished learning with the DUET, they had become accustomed to the new device. Subjects had used the DUET2 exclusively since upgrade in this study; however, at 6 months reverted for testing to the DUET. Acute testing with the DUET after 6 months resulted in a deterioration of SRT, because subjects were no longer familiar with the stimulation provided with the DUET audio processor. Over the same period (upgrade to 6 months), the SRT in quiet with the DUET2 did not improve. However, the SRT in quiet was significantly better at 6 months with the DUET2 compared to the DUET. This indicates that subjects became accustomed to the DUET2 stimulation. In the more difficult test situation (SRT in noise), the speech reception was significantly better with the DUET2 at 6 months than with the DUET at 6 months. One could argue that this comparison is unfair because at this test session subjects had 6 months experience with the DUET2, but were tested acutely with the DUET. However, comparison of the SRT in noise showed that the SRT in noise was significantly better after 6 months with the DUET2 than with the DUET at upgrade. This suggests that the DUET2 offers tangible benefits compared to the DUET.
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
1028
A. Kleine Punte et al.
Likewise, monosyllable word recognition with the DUET2 showed a significant improvement compared to the DUET between upgrade and 6 months, and after 6 months. The effect was significant both in quiet and in noise. Significantly better performance with the DUET2 was reached between upgrade and 3 months, and the benefit was still appreciable after 6 months, even though there was no improvement in the monosyllable word recognition with the DUET2 between 3 and 6 months. It appears that subjects need time and listening experience to benefit from features available in the DUET2 and to become accustomed to the new device. We would speculate, as Lorens et al. [13] indicated, that a more pronounced benefit of the DUET2 would become apparent after an even longer period. Several authors have shown that up to 12 months of use is necessary for patients to appreciate thoroughly the benefit of a new sound coding strategy [14–16]. In particular, the results of the Vermeire et al. [14] study also indicate that the benefits of the coding strategy tested cannot be attributed to experience or general learning alone. Likewise, we hypothesize that the improvements in the present study with the DUET2 could not be attributed to a general learning effect or experience alone, seeing as these subjects were experienced EAS users, and were accustomed to the test methods. Thus, without intervention, no improvement would be expected over time. However, comparing the results with the DUET at upgrade to the DUET2 after 6 months of use, we see that the subjects with the DUET2 perform better. Moreover, the subjects in the present study saw a clear subjective benefit with the DUET2 over the DUET between upgrade and 6 months, and with the DUET2 over the DUET after 6 months in the sound quality of speech and music. All subjects preferred the DUET2 over the DUET audio processor and did not opt for using the DUET after the trial period. The overall improvement in speech reception, word recognition, sound, and music quality with the DUET2 could be attributed to the coding strategy HDCIS that expands the low frequency range of the CI, or to the new microphone and higher amplification of the DUET2. However, it is not possible to pinpoint conclusively the difference between the DUET and the DUET2 that accounts for the greatest improvement observed. Conclusion The DUET2 audio processor for EAS can significantly improve speech perception in noise and sound quality compared to the DUET in experienced EAS users.
Acknowledgements We would gratefully like to acknowledge, from MEDEL GmbH, Edda Amann for statistical analyses, and Martin Eisendle and Una Doyle for writing assistance on a version of this manuscript. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. References [1] Helbig S, Van de HP, Kiefer J, Baumann U, Kleine-Punte A, Brockmeier H, et al. Combined electric acoustic stimulation with the PULSARCI(100) implant system using the FLEX (EAS) electrode array. Acta Otolaryngol 2011;131:585–95. [2] von Ilberg C, Kiefer J, Tillein J, Pfenningdorff T, Hartmann R, Sturzebecher E, et al. Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61: 334–40. [3] Skarzynski H, Lorens A, Piotrowska A. A new method of partial deafness treatment. Med Sci Monit 2003;9: CS20–4. [4] Lorens A, Zgoda M, Skarzynski H. A new audio processor for combined electric and acoustic stimulation for the treatment of partial deafness. Acta Otolaryngol 2012;132:739–50. [5] von Ilberg C, Kiefer J, Tillein J, Pfenningdorff T, Hartmann R, Sturzebecher E, et al. Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61:334–40. [6] von Ilberg C, Kiefer J, Tillein J, Pfenningdorff T, Hartmann R, Sturzebecher E, et al. Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61: 334–40. [7] Helbig S, Baumann U. Acceptance and fitting of the DUET device - a combined speech processor for electric acoustic stimulation. Adv Otorhinolaryngol 2010;67:81–7. [8] Kuss P, Deibl M, Shepherd D BH. The OPUS 2 user survey. Conference Proceedings. 2008. [9] Lorens A, Zgoda M, Skarzynski H. A new audio processor for combined electric and acoustic stimulation for the treatment of partial deafness. Acta Otolaryngol 2012;132:739–50. [10] Arnoldner C, Riss D, Brunner M, Durisin M, Baumgartner WD, Hamzavi JS. Speech and music perception with the new fine structure speech coding strategy: preliminary results. Acta Otolaryngol 2007;127:1298–303. [11] Riss D, Hamzavi JS, Blineder M, Honeder C, Ehrenreich I, Kaider, et al. FS4, FS4-p, and FSP: a 4-month crossover study of 3 fine structure sound-coding strategies. Ear Hear 2014;35:e272–81. [12] van Wieringen A, Wouters J. LIST and LINT: sentences and numbers for quantifying speech understanding in severely impaired listeners for Flanders and the Netherlands. Int J Audiol 2008;47:348–55. [13] Lorens A, Zgoda M, Skarzynski H. A new audio processor for combined electric and acoustic stimulation for the treatment of partial deafness. Acta Otolaryngol 2012;132:739–50. [14] Vermeire K, Punte AK, Van de HP. Better speech recognition in noise with the fine structure processing coding strategy. ORL J Otorhinolaryngol Relat Spec 2010;72:305–11.
Speech reception and sound quality with DUET2 for EAS
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
[15] Riss D, Arnoldner C, Reiss S, Baumgartner WD, Hamzavi JS. 1-year results using the Opus speech processor with the fine structure speech coding strategy. Acta Otolaryngol 2009;129:988–91.
1029
[16] Riss D, Arnoldner C, Baumgartner WD, Kaider A, Hamzavi JS. A new fine structure speech coding strategy: speech perception at a reduced number of channels. Otol Neurotol 2008;29:784–8.
ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20
Improved speech reception and sound quality with the DUET2 audio processor for electric acoustic stimulation Andrea Kleine Punte, Griet Mertens, Ellen Cochet, Marc De Bodt & Paul Van de Heyning To cite this article: Andrea Kleine Punte, Griet Mertens, Ellen Cochet, Marc De Bodt & Paul Van de Heyning (2015) Improved speech reception and sound quality with the DUET2 audio processor for electric acoustic stimulation, Acta Oto-Laryngologica, 135:10, 1022-1029, DOI: 10.3109/00016489.2015.1050605 To link to this article: http://dx.doi.org/10.3109/00016489.2015.1050605
Published online: 13 Jun 2015.
Submit your article to this journal
Article views: 26
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ioto20 Download by: [Chelsea & Westminster NHS Trust Dept of Urology]
Date: 04 October 2015, At: 17:10
Acta Oto-Laryngologica. 2015; 135: 1022–1029
ORIGINAL ARTICLE
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
Improved speech reception and sound quality with the DUET2 audio processor for electric acoustic stimulation
ANDREA KLEINE PUNTE, GRIET MERTENS, ELLEN COCHET, MARC DE BODT & PAUL VAN DE HEYNING Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University Hospital, University of Antwerp, Belgium
Abstract Conclusion: The results show that the DUET2 offers users speech perception that is equivalent to or better than the DUET. Moreover, the DUET2 offers subjective benefits above those provided by the DUET. Background: The DUET is a combination of hearing aid and CI in one device for electric acoustic stimulation. Since its introduction: a second generation, the DUET2, has been developed. This study aimed to investigate the benefits of the DUET2 compared to the DUET. Methods: Speech reception was determined in quiet and in noise. The sound quality of speech and music was rated using a visual analogue scale. Test intervals were at upgrade and at 3 and 6 months after upgrade. Results: Speech reception in quiet and in noise was significantly better than with the DUET after 6 months. For sentence reception in quiet, the SRT with the DUET2 did not change significantly between test intervals. Sentence reception in noise with the DUET2 improved significantly between 3 and 6 months and upgrade and 6 months. After 6 months, speech reception in quiet and in noise with the DUET2 was significantly better than with the DUET. Subjects rated the sound quality of speech and of music with the DUET2 significantly better than with the DUET.
Keywords: Speech processor, electric acoustic stimulation, sound quality, cochlear implants, subjective benefit, auditory outcome measures
Introduction Patients with residual hearing in the low frequencies and severe-to-profound hearing loss in the higher frequencies can benefit from a combination of electrical and acoustical hearing in the same ear [1–4]. While hearing aids (HAs) are particularly effective at providing amplification of low frequencies, the compensation of severe hearing loss in the high frequency range (> 1000 Hz; > 70 dB hearing loss) is often insufficient [5]. Thus, to provide auditory stimulation over a complete frequency range (up to 6000 Hz), a HA is used in combination with electric stimulation, in the form of a cochlear implant (CI) [6]. The combination of both devices in one ear is called electric acoustic stimulation (EAS). The use of
multiple devices simultaneously to deliver electrical and acoustical stimulation proves cumbersome because multiple devices require different types of batteries, with different battery life spans, and inthe-ear HAs provide inadequate amplification to patients with moderate hearing loss at low frequency thresholds (< 500 Hz) [7]. The DUET audio processor was, therefore, developed in order to offer a combination of HA and CI in one device [7]. The HA of the DUET was specially designed to achieve acoustic amplification in the low frequencies between 125–1500 Hz, while the mid-to-high frequencies are transmitted electrically via the CI with the same audio processor. A second generation of this device called the DUET2 has subsequently been developed. The
Correspondence: Paul Van de Heyning, Antwerp University Hospital, Department of Otolaryngology and Head and Neck Surgery, Wilrijkstraat 10, 2650 Edegem, Belgium. Tel: +0032-38214059. Fax: +0032-38250536. E-mail: [email protected]
(Received 8 April 2015; accepted 3 May 2015) ISSN 0001-6489 print/ISSN 1651-2251 online 2015 Informa Healthcare DOI: 10.3109/00016489.2015.1050605
Speech reception and sound quality with DUET2 for EAS
1023
Table 1. Demographic information. Subject Gender Etiology of Ear Contralateral ID Deafness Implanted Amplification
Electrode Implant Type
Age (years)
Duration of DUET Experience (months)
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
First Upgrade Implantation 1a*
Male
Ototoxicity Right
Bilateral EAS
Medium
1b*
Male
Ototoxicity Left
Bilateral EAS
FLEXSOFT PULSAR
2
Male
Trauma
Left
Hearing Aid
3
Male
Hereditary
Left
No
4
Female
Ototoxicity Left
5
Male
Hereditary
Left
COMBI40+ 47.7
53.2
43,6
47.7
53.2
43,5
Medium
COMBI40+ 60.8
66.1
43,9
Medium
COMBI40+ 69.0
75.2
43,6
No
Medium
COMBI40+ 50.3
54.2
43,3
Hearing Aid
FLEX24
PULSAR
58.3
60.9
27,3
24
6
Female
Hereditary
Right
Hearing Aid
FLEX
PULSAR
71.5
73.6
22,7
7
Female
Hereditary
Right
Hearing Aid
FLEX24
PULSAR
64.6
68.1
38,6
SONATA
21.8
23.0
12,9
8
Male
Ototoxicity Right
No
24
FLEX
*Bilaterally upgraded subject. Each ear was treated as an individual case.
DUET2 is different in design to the DUET; it has improved signal processing capabilities, includes a remote control and a battery alert function [8,9]. With the DUET2 audio processor, the latest speech coding strategies offered by the Maestro fitting software can be implemented. The output of the HA is also greater than with the first generation DUET audio processor (DUET 40dB max vs DUET2 43 dB max). Furthermore, the DUET2 uses an improved microphone compared to the DUET. The speech coding strategies currently available for the DUET are: High Definition Continuous Interleaved Sampling (HDCIS), Fine Structure Processing (FSP), Fine Structure4 (FS4), and FS4p (parallel signal processing) (as cited in Arnolder et al. [10] and Riss et al. [11]). This study aimed to investigate the benefits of the DUET2 compared to the DUET speech processor in terms of speech perception, sound quality of speech and music, and overall user satisfaction.
Materials and methods Subjects Eight Dutch speaking patients were included in this study (five male and three female). The mean age at first implantation was 55.5 ± 15.9 years. The mean age at upgrade was 59.3 ± 16.7 years. For further demographic data see Table I. One subject used bilateral EAS; seven subjects were unilateral EAS users. All subjects were experienced DUET users. The average duration of DUET experience before upgrade was 2.9 ± 1.0 year.
Methods All subjects were upgraded from the DUET to the DUET2 audio processor by simply transferring the individual subject’s DUET program to the DUET2. The bilateral EAS user was bilaterally upgraded, both ears were tested independently with the processor taken off and the contralateral ear plugged. Both processors were fitted according to the instructions in the MAESTRO software manual, and according to the DUET System Data Sheet. The ‘electrical part’ of the EAS was set using the reduced overlapping frequency range, where the programmed CI frequency range starts at the cross-over frequency of the audiogram (defined as that frequency where the audiogram passes the 65 dB HL point). Subjects used the CIS+ speech coding strategy with the DUET and the HDCIS speech coding strategy with the DUET2. For the ‘acoustical part’ of the DUET and the DUET2, the half-gain rule was used: the threshold of a given frequency was divided in half to obtain the predicted gain. Speech reception thresholds (SRT) in quiet and in noise were assessed using the Leuven Intelligibility Sentence Test (LIST) [12] in an adaptive procedure. In quiet and in noise the initial speech level was 65 dB SPL. For the testing in noise condition, speechweighted stationary noise, based on the long-term average speech spectrum of the sentences, was used with the noise level fixed at 65 dB SPL. The level of the sentences varied in steps of 2 dB adaptively in a one-down-, one-up-procedure according to the subject’s response. The SRT was ascertained on the basis of the level of the last six sentences of one list, including an imaginary 11th sentence.
1024
A. Kleine Punte et al.
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
A
B
Figure 1. Mean outcome of the Leuven Intelligibility Sentence Test (adaptive auditory speech test) in (A) quiet (dB HL) and (B) noise (dB SNR), using the DUET or the DUET2 audio processor (n = 9). Error bars represent standard deviation.
Monosyllable word recognition testing was performed using a fixed procedure in quiet with a speech level of 65 dB SPL and in noise at +5 dB signal-tonoise ratio (SNR). The sound quality of speech and music was rated (0–100) using a visual analog scale (VAS). The sound files used were taken from a Flemish listening book and instrumental versions of popular songs. Both sound files were presented in free field at a comfortable level, 1 m in front of the subject. The test intervals used were at the time of upgrade to the DUET2, 3 months after upgrade to the DUET2, and 6 months after upgrade. At upgrade, subjects were tested with the DUET and the DUET2 audio processor. At the 3-month test interval, subjects were tested with the DUET2 only. Ethics approval Local ethics committee approval was obtained. All subjects gave written informed consent prior to participation in this study.
Statistical analyses SRT levels (mean ± SD) for LIST sentence test results in quiet (dB HL) and in noise (dB SNR) for the different audio processors and test intervals are presented. Percentage values for monosyllable speech recognition in quiet and in noise and the average score on the VAS are shown for the two audio processors and the intervals tested (mean ± SD). Paired sample t-tests were used to analyze differences between the two audio processors and between the test intervals. Repeated measure (RM) ANOVA was performed to test the effect of time with the DUET2. If performance was stable at the upgrade interval, the DUET results at upgrade were compared to the DUET2 results after 6 months of listening experience, using the paired sample t-test. The normality of the distribution was confirmed using the Kolmogorov-Smirnov test. Missing data were not replaced but treated as missing values. A p-value < 0.05 was determined as statistically significant. IBM SPSS Statistics 19.0 software (IBM,
Speech reception and sound quality with DUET2 for EAS
1025
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
A
B
Figure 2. Mean percentage correct monosyllable speech recognition in (A) quiet; and (B) noise, using the DUET or the DUET2 audio processor (n = 9). Error bars represent standard deviation.
Armonik, NY) was used for the statistical analyses. Graphs were created in Microsoft Office Excel 2010 (http//www.microsoft.com). Results Adaptive speech perception Figure 1A shows the mean SRT in quiet determined using the LIST (dB HL). The SRT with the DUET2 at upgrade in quiet (32.8 ± 13.4 dB) did not change significantly (p = 0.201) compared to the SRT in quiet with the DUET (29.9 ± 9.4 dB). After 3 months, the SRT with the DUET2 in quiet was 32.6 ± 8.3 dB. After 6 months, the SRT with the DUET in quiet was 34.9 ± 10.3 dB. The SRT with the DUET2 in quiet after 6 months (30.7 ± 8.5 dB) was significantly better than with the DUET at 6 months (p = 0.035). Between upgrade and 6 months, the SRT in quiet worsened significantly (p = 0.035) with the DUET. In contrast, DUET2 results improved slightly, but not significantly, over time (F(2;16) = 0.474; p = 0.631).
No significant difference was found between the DUET at upgrade and DUET2 after 6 months of listening experience (p = 0.539). Figure 1B shows the mean SRT in noise determined using the LIST (dB SNR). There was no significant difference (p = 1.000) in the SRT in noise between the two audio processors at upgrade (DUET = 7.0 ± 4.8 dB; DUET2 = 7.0 ± 5 dB). After 3 months, the SRT in noise with the DUET2 was 6.7 ± 3.9 dB. After 6 months, the SRT with the DUET in noise was 9.7 ± 3.9 dB. The SRT with the DUET2 in noise after 6 months (3.3 ± 2.7 dB) was significantly better than with the DUET at 6 months (p = 0.001). Between upgrade and 6 months, the SRT in noise was not significantly different with the DUET (p = 0.104). In contrast, the SRT in noise with the DUET2 changed significantly over time (F(2;16) = 6.041; p = 0.011). Between upgrade and 3 months, the difference was not significant (p = 0.813). However, between 3–6 months, the SRT in noise with the DUET2 improved significantly (p = 0.002). The SRT in noise with the DUET2 after 6 months of listening
1026
A. Kleine Punte et al.
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
A
B
Figure 3. Mean level of satisfaction with (A) speech; and (B) music using the DUET or the DUET2 audio processor (n = 9). Error bars represent standard deviation.
experience was significantly better than with the DUET at upgrade (p = 0.005). Monosyllable word recognition Figure 2A shows the monosyllable word recognition in quiet (percentage correct). The monosyllable word recognition at upgrade, with the DUET in quiet, was 48.5 ± 19.4%. The monosyllable word recognition at upgrade, with the DUET2 in quiet (40.9 ± 21.1%), did not change significantly compared with the monosyllable word recognition in quiet with the DUET. After 3 months, the monosyllable word recognition with the DUET2 in quiet was 52.0 ± 20.0%. After 6 months, the monosyllable word recognition with the DUET in quiet was 37.4 ± 16.8%. The monosyllable word recognition with the DUET2 in quiet after 6 months (60.6 ± 20.5%) was significantly greater than with the DUET after 6 months (p = 0.028). Between upgrade and 6 months, the monosyllable word recognition in quiet with the DUET did not change significantly (p = 0.186). With the DUET2, however, there was a significant effect over time (F
(2;16) = 5.819; p = 0.013). The monosyllable word recognition in quiet improved significantly with the DUET2 between upgrade and 3 months (p = 0.033). The improvement in monosyllable word recognition in quiet with the DUET2 was not significantly different between 3- and 6-months (p = 0.135). The monosyllable word recognition in quiet, with the DUET2, after 6 months of listening experience, was significantly better than with the DUET at upgrade (p = 0.018). Figure 2B shows the mean percentage monosyllable word recognition in noise (+5 dB SNR). The monosyllable word recognition at upgrade, with the DUET in noise, was 33.3 ± 24.8%. The monosyllable word recognition at upgrade, with the DUET2 in noise (31.8 ± 20.5%), did not change significantly compared with the monosyllable word recognition at upgrade in noise with the DUET (p = 0.806). After 3 months, the monosyllable word recognition with the DUET2 in noise was 40.4 ± 22.3%. After 6 months, the monosyllable word recognition with the DUET in noise was 27.3 ± 13.8%. Monosyllable word recognition with the DUET2 in noise, after 6 months
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
Speech reception and sound quality with DUET2 for EAS (44.4 ± 21.4%), was significantly greater than with the DUET (p = 0.031). Between upgrade and 6 months, the monosyllable word recognition in noise with the DUET did not change significantly (p = 0.428). Similarly, between the time of upgrade and 6 months, word recognition in noise did not change significantly with the DUET2 (F(2;16) = 2.535; p = 0.111). The monosyllable word recognition in noise with the DUET2, after 6 months of listening experience, was significantly better than with the DUET at upgrade (p = 0.032). Sound quality of speech and music The mean level of satisfaction with the sound quality of speech, determined using a VAS, is shown in Figure 3A. At upgrade, the level of satisfaction with the sound quality of speech with the DUET was not significantly different to the DUET2 (p = 0.380). However, after 6 months, the level of satisfaction with the sound quality of speech with the DUET2 was rated significantly better than with the DUET (p = 0.028). The level of satisfaction with the sound quality of speech with the DUET was not significantly different between upgrade and 6 months (p = 0.923). Similarly, the level of satisfaction with the sound quality of speech with the DUET2 did not improve significantly over time (F(2;16) = 1.072; p = 0.366). The level of satisfaction with the sound quality of speech with the DUET2 after 6 months was significantly better than with the DUET at upgrade (p = 0.025). The mean level of satisfaction with the sound quality of music, determined using a VAS, is shown in Figure 3B. At upgrade, the level of satisfaction with the sound quality of music with the DUET was not significantly different to the DUET2 (p = 0.311). After 6 months, the level of satisfaction with the sound quality of music with the DUET2 was rated significantly better than with the DUET (p = 0.008). The level of satisfaction with the sound quality of music with the DUET was not significantly different between upgrade and 6 months (p = 0.838). The DUET2 results showed a tendency towards a significant effect of time (F(2;16) = 3.086; p = 0.074). This trend towards a significant improvement with the DUET2 in the level of satisfaction with the sound quality of music, was observed between 3 and 6 months (p = 0.051). The sound quality of music with the DUET2 after 6 months was significantly better than with the DUET at upgrade (p = 0.036). Subjects reported a more natural sound quality with the DUET2 compared to the DUET, and ease of listening also improved with the DUET2. Overall, subjects preferred the DUET2 compared to the DUET. After the trial period, subjects were offered
1027
their original audio processor back, but all subjects declined and continued using the DUET2 audio processor. Discussion The results of the present study show that the DUET2 offers users speech perception and recognition that is equivalent to, or better than, the DUET. Moreover, the DUET2 offers subjective benefits above those provided by the DUET, such as improved sound quality of speech and improved sound quality of music. Furthermore, the data show that it can take time for adult CI users to become accustomed to their new audio processor. Lorens et al. [13] suggests that the relatively stable results found over time with the DUET indicated that the learning with the DUET was complete before upgrade to the DUET2. Only patients with a minimum of 12 months experience were included in the Lorens et al. study. Similarly, in the present study, subjects had over 12 months of experience with the DUET2 (2.9 ± 1.0 year). The SRT in quiet with the DUET deteriorated significantly between upgrade and 6 months. While the SRT results in noise with the DUET did not change significantly between upgrade and 6 months, the SRT showed a trend towards a decrease. This result suggests that learning with the DUET was complete before upgrade. However, not only had subjects finished learning with the DUET, they had become accustomed to the new device. Subjects had used the DUET2 exclusively since upgrade in this study; however, at 6 months reverted for testing to the DUET. Acute testing with the DUET after 6 months resulted in a deterioration of SRT, because subjects were no longer familiar with the stimulation provided with the DUET audio processor. Over the same period (upgrade to 6 months), the SRT in quiet with the DUET2 did not improve. However, the SRT in quiet was significantly better at 6 months with the DUET2 compared to the DUET. This indicates that subjects became accustomed to the DUET2 stimulation. In the more difficult test situation (SRT in noise), the speech reception was significantly better with the DUET2 at 6 months than with the DUET at 6 months. One could argue that this comparison is unfair because at this test session subjects had 6 months experience with the DUET2, but were tested acutely with the DUET. However, comparison of the SRT in noise showed that the SRT in noise was significantly better after 6 months with the DUET2 than with the DUET at upgrade. This suggests that the DUET2 offers tangible benefits compared to the DUET.
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
1028
A. Kleine Punte et al.
Likewise, monosyllable word recognition with the DUET2 showed a significant improvement compared to the DUET between upgrade and 6 months, and after 6 months. The effect was significant both in quiet and in noise. Significantly better performance with the DUET2 was reached between upgrade and 3 months, and the benefit was still appreciable after 6 months, even though there was no improvement in the monosyllable word recognition with the DUET2 between 3 and 6 months. It appears that subjects need time and listening experience to benefit from features available in the DUET2 and to become accustomed to the new device. We would speculate, as Lorens et al. [13] indicated, that a more pronounced benefit of the DUET2 would become apparent after an even longer period. Several authors have shown that up to 12 months of use is necessary for patients to appreciate thoroughly the benefit of a new sound coding strategy [14–16]. In particular, the results of the Vermeire et al. [14] study also indicate that the benefits of the coding strategy tested cannot be attributed to experience or general learning alone. Likewise, we hypothesize that the improvements in the present study with the DUET2 could not be attributed to a general learning effect or experience alone, seeing as these subjects were experienced EAS users, and were accustomed to the test methods. Thus, without intervention, no improvement would be expected over time. However, comparing the results with the DUET at upgrade to the DUET2 after 6 months of use, we see that the subjects with the DUET2 perform better. Moreover, the subjects in the present study saw a clear subjective benefit with the DUET2 over the DUET between upgrade and 6 months, and with the DUET2 over the DUET after 6 months in the sound quality of speech and music. All subjects preferred the DUET2 over the DUET audio processor and did not opt for using the DUET after the trial period. The overall improvement in speech reception, word recognition, sound, and music quality with the DUET2 could be attributed to the coding strategy HDCIS that expands the low frequency range of the CI, or to the new microphone and higher amplification of the DUET2. However, it is not possible to pinpoint conclusively the difference between the DUET and the DUET2 that accounts for the greatest improvement observed. Conclusion The DUET2 audio processor for EAS can significantly improve speech perception in noise and sound quality compared to the DUET in experienced EAS users.
Acknowledgements We would gratefully like to acknowledge, from MEDEL GmbH, Edda Amann for statistical analyses, and Martin Eisendle and Una Doyle for writing assistance on a version of this manuscript. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. References [1] Helbig S, Van de HP, Kiefer J, Baumann U, Kleine-Punte A, Brockmeier H, et al. Combined electric acoustic stimulation with the PULSARCI(100) implant system using the FLEX (EAS) electrode array. Acta Otolaryngol 2011;131:585–95. [2] von Ilberg C, Kiefer J, Tillein J, Pfenningdorff T, Hartmann R, Sturzebecher E, et al. Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61: 334–40. [3] Skarzynski H, Lorens A, Piotrowska A. A new method of partial deafness treatment. Med Sci Monit 2003;9: CS20–4. [4] Lorens A, Zgoda M, Skarzynski H. A new audio processor for combined electric and acoustic stimulation for the treatment of partial deafness. Acta Otolaryngol 2012;132:739–50. [5] von Ilberg C, Kiefer J, Tillein J, Pfenningdorff T, Hartmann R, Sturzebecher E, et al. Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61:334–40. [6] von Ilberg C, Kiefer J, Tillein J, Pfenningdorff T, Hartmann R, Sturzebecher E, et al. Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61: 334–40. [7] Helbig S, Baumann U. Acceptance and fitting of the DUET device - a combined speech processor for electric acoustic stimulation. Adv Otorhinolaryngol 2010;67:81–7. [8] Kuss P, Deibl M, Shepherd D BH. The OPUS 2 user survey. Conference Proceedings. 2008. [9] Lorens A, Zgoda M, Skarzynski H. A new audio processor for combined electric and acoustic stimulation for the treatment of partial deafness. Acta Otolaryngol 2012;132:739–50. [10] Arnoldner C, Riss D, Brunner M, Durisin M, Baumgartner WD, Hamzavi JS. Speech and music perception with the new fine structure speech coding strategy: preliminary results. Acta Otolaryngol 2007;127:1298–303. [11] Riss D, Hamzavi JS, Blineder M, Honeder C, Ehrenreich I, Kaider, et al. FS4, FS4-p, and FSP: a 4-month crossover study of 3 fine structure sound-coding strategies. Ear Hear 2014;35:e272–81. [12] van Wieringen A, Wouters J. LIST and LINT: sentences and numbers for quantifying speech understanding in severely impaired listeners for Flanders and the Netherlands. Int J Audiol 2008;47:348–55. [13] Lorens A, Zgoda M, Skarzynski H. A new audio processor for combined electric and acoustic stimulation for the treatment of partial deafness. Acta Otolaryngol 2012;132:739–50. [14] Vermeire K, Punte AK, Van de HP. Better speech recognition in noise with the fine structure processing coding strategy. ORL J Otorhinolaryngol Relat Spec 2010;72:305–11.
Speech reception and sound quality with DUET2 for EAS
Downloaded by [Chelsea & Westminster NHS Trust Dept of Urology] at 17:10 04 October 2015
[15] Riss D, Arnoldner C, Reiss S, Baumgartner WD, Hamzavi JS. 1-year results using the Opus speech processor with the fine structure speech coding strategy. Acta Otolaryngol 2009;129:988–91.
1029
[16] Riss D, Arnoldner C, Baumgartner WD, Kaider A, Hamzavi JS. A new fine structure speech coding strategy: speech perception at a reduced number of channels. Otol Neurotol 2008;29:784–8.
