Appendix 2. Summary of Selected Adult Bilateral Cochlear Implant Studies

Study Objectives Participants Methods Results Conclusions

Buss E, et al. Evaluate the 26 adults bilaterally CNC words in quiet, CUNY sentences in Mean bilateral CNC scores improved by 5.8% at Bilateral improvements may Multicenter U.S. benefits of bilateral implanted at 5 US CCITT noise at individually set SNRs. the 1-month interval and 11% at the 12-month continue through one year of bilateral MED-EL implant centers. All but 1 of Speech was presented from the front and interval. CUNY sentences in noise showed bilateral implant use. cochlear implantation performance in the participants had noise from the front, 90º from the right or 90º significant bilateral benefit at 6 and 12 months differences occur, but an study: Speech adults. simultaneous from the left. All stimuli were presented via post implant. Median improvements were individual’s ear dominance is not perception over the surgeries. direct audio input which bypasses the approximately 38% due to head shadow effects necessarily consistent over time. first year of use. compression circuitry of the speech and 2-8% due to binaural summation effects. At Binaural squelch benefits may processor. Testing was conducted at 1, 3, the 12 month interval, binaural squelch benefits require longer periods of use Ear Hear. 2008 6, and 12 months post-implant. compared to other bilateral Jan;29(1):20-32. were observed for most subjects with a median improvement of approximately 11%. benefits such as head shadow Speech recognition and summation effects.

Dunn CC, et al. Identify the result of 7 adult simultaneously Conversion to 16 channel HiRes included Immediate crossover: 5 of 6 tested participants Large improvement (30-60%) in Effects of converting conversion from implanted bilateral providing both HiRes P (5156 pps & PW = had significant improvement with HiRes and 1 speech recognition in noise with bilateral cochlear CIS to a Clarion CII recipients 11μs) and HiRes S (2900 pps & PW = 11μs) participant had significant decline with HiRes. HiRes after 1 month’s use implant subjects to a HiResolution who had used 8 on each participants’ speech processor. 1 month HiRes P vs. HiRes S: no significant compared to baseline CIS. strategy with strategy; evaluate channel CIS (813 pps Speech recognition testing was completed in difference for the group; HiRes P was better for 2 Improvement maintained at 3 increased rate and speech recognition & PW = 75μs) for at CIS prior to conversion and in HiRes P and of 7 participants. months; 4 out of 5 maintained number of channels. with HiResolution least 18 months. HiRes S immediately after conversion and improvement at 6+ months. Paired (HiRes P) after 1 month’s use alternating between 1 month best HiRes vs. CIS: HiRes scores on Ann of Oto Rhinol sentences in noise improved by 30-60% for 6 No difference between HiRes P and HiResolution HiRes P & HiRes S daily. Speech and HiRes S strategies. Laryngol 2006. 115: Sequential (HiRes recognition was evaluated again after 3 & 6 participants compared to CIS. 425-432. S). months use of the preferred program(s). 6+ month HiRes vs. CIS: 5 participants still used Authors suggest additional study Speech recognition HiRes and scored significantly better with HiRes of the effects of rate vs. channel Speech recognition: CUNY sentences at 70 number. dbC in multi-talker babble with speech and than CIS; re-test CIS after 6 months HiRes noise from the front at individually set SNRs. experience was improved over initial CIS testing All testing was conducted in the bilateral for 2 participants. condition.

Grantham DW, et al. Assess the 22 bilaterally Localization: 43 loudspeaker array spaced Unilateral condition: Ĉ was near chance for all Individuals with bilateral cochlear Horizontal-plane horizontal implanted adult along a 180º arc of which 17 speakers along participants. Unilateral better ear performance implants localize well on the localization of noise localization ability recipients of devices a 160º arc were active. White Gaussian was near chance (47.9º). In the unilateral horizontal plane using both and speech signals by of bilaterally from 6 CI centers. All noise bursts and speech stimuli (“hey”) were condition, participants had a strong bias to hear all devices but not when using only postlingually deafened implanted adults for but two of the used, both filtered from 100 – 4k Hz. stimuli as originating from the side with the active one device. They localized adults fitted with noise and speech participants had Results were reported as adjusted constant device. speech stimuli slightly better than bilateral cochlear stimuli and simultaneous error (Ĉ) for which 50.5º is chance. Bilateral condition: Ĉ varied from 8.1º to 43.4º noise stimuli. The ability to implants. compare surgeries. ILD & ITD cues: Low-pass, high-pass, and with a mean of 24.1º for noise bursts. Average Ĉ localize had stabilized by localization abilities slow-onset noise stimuli were included in for speech (21.5º) was significantly lower. 5 months of bilateral device use Ear Hear. 2007 over time. for most participants. Aug;28(4):524-41. addition to the noise burst and speech For all but 2 participants who were retested after Investigate the stimuli described above for sub groups of For horizontal plane localization, Localization 15 months of bilateral device use, there was no contributions of ILD the participants. significant change in performance. Two bilaterally implanted adults rely and ITD cues for Testing was conducted for each CI participants had considerable improvement, primarily on ILD cues and are horizontal individually and bilaterally after 5 months however their Ĉ decreased by half. unable to benefit from ITD cues. localization with device use for all participants and then noise. There was no significant difference in localization repeated 10 months later for 12 participants. between using the noise bursts and the high-pass or slow-onset noise. There was, however, a significant increase in errors for the low-pass stimuli compared to the noise bursts. Study Objectives Participants Methods Results Conclusions

Grantham DW, et al. Measure ITDs and 11 bilaterally ITD and ILD thresholds were measured ILD thresholds were significantly lower with Poor sensitivity to ITD with this Interaural time and ILDs in bilaterally implanted adults who using acoustic stimuli (200-msec Gaussian compression turned off. The mean ILD threshold task supports the notion that ITD level difference implanted adults were a subset of the noise burst) via headphones. Thresholds was 3.8 dB (range = 1.2 - 10.7) with compression cues can not be used for thresholds for using noise signals; participants in were measured both with compression turned on compared to a mean threshold of 1.9 dB localization of noise stimuli by acoustically presented compare ILD and Grantham et al 2007 activated on the speech processor (~45 dB (range = 0.9 - 3.3) with compression turned off. bilaterally implanted adults (using signals in post- ITD thresholds to listed above. threshold) and with compression ITD thresholds were poor; 5 were ~400 - 1000μs a CIS envelope extraction localization error deactivated. An adaptive 2-alternative strategy). Horizontal plane lingually deafened 3 participants had ~5 with the rest being > 1000 μs and two individuals scores. forced-choice procedure was used where localization is primarily dependent adults fitted with months and 7 were not able to distinguish the direction up to the participant indicated if the noise was on ILD cues. bilateral cochlear participants had ~15 10,000 μs. implants using CIS+ months of bilateral moving from right to left or left to right. ILD, particularly with compression off, correlated processing. device use. Feedback was provided. with the total error score on the localization task ILD and ITD thresholds were compared to Ear Hear. 2008 where as ITD did not correlate. Jan;29(1):33-44. the error scores obtained in the localization task described in Grantham et al 2007 ITD/ILD Thresholds (above).

Laszig R, et al. Evaluate speech 37 adults with bilateral Speech recognition: FMW words and OLSA Speech recognition in quiet: Binaural benefit Bilateral CI use provides Benefits of bilateral recognition and CIs, 15 were or HMS sentences at 70 dB SPL; OLSA demonstrated compared to either unilateral advantages to some recipients electrical stimulation localization abilities sequentially implanted sentences in noise (CCITT) using an condition for OLSA sentences and compared to over unilateral CI use for listening with the Nucleus of adults who are (0.4 – 5.6 yrs between adaptive procedure resulting in a SNR for the poorer ear for FMW & HSM sentences. in quiet and in noise and for most cochlear implant in bilateral cochlear surgeries) and 22 had 50% correct; HMS sentences at 70 dB SPL Speech recognition in noise: Binaural benefit recipients for localization. adults: 6-month implant recipients. both surgeries with a fixed 10 dB SNR. noted with either unilateral condition for adaptive Head shadow is the most robust postoperative results. simultaneously. Localization: 12 loudspeakers spaced 30º OLSA sentences and compared to the poorer ear effect, although some individuals Participants were Otol Neurotol 2004; apart in a circle around the participant using for HMS sentences with the speech and noise seem to benefit from binaural from several German- a shortened HMS sentence at 65-70 or 55- both from the front. squelch and binaural redundancy 25:958-68. speaking clinics in 60 dB SPL. Results are reported as RMS For spatially separated speech in noise, there was in some situations. Speech recognition Germany and error. Localization Switzerland. a consistent interaural performance advantage for Bilateral cochlear implantation the ear closest to the speech source whether or allows binaural auditory not the better ear was closest to the speech signal processing that can assist with (head shadow benefit). Bilateral stimulation communication in everyday always provided superior performance than listening situations. unilateral listening with either ear when ipsilateral to the noise source. Localization: 15 of 16 participants had better localization with bilateral device use than with unilateral use. In the unilateral condition, the tendency was to respond on the side of the device.

2 Study Objectives Participants Methods Results Conclusions

Litovsky RY, et al. Investigate speech 17 adult participants Speech recognition using an adaptive Speech recognition: Bilateral advantage seen Results indicate advantages for Bilateral cochlear recognition and (14 postlingual and 3 procedure with 4-talker babble and BKB when the babble was on the side of the poorer CI. bilateral CI use over unilateral use implants in adults and localization abilities perilingual) who sentences that results in a SNR for 50% Localization: Bilateral performance was better for localization and understanding children. for adults and received CIs in correct (BKB-SIN). Speech was presented than either unilateral performance. speech in noise. Since children with simultaneous from the front and noise from the front, 90º participants only had 3 months of Arch Otolaryngol bilateral CIs. procedures. right, and 90º left. Adults: Bilateral leads to better localization bilateral CI experience, the Head Neck Surg performance and speech intelligibility when the potential bilateral benefit from 2004; 130:648-55 Localization: 8 loudspeakers spaced along a noise is near the poorer of the two . 140º arc using bursts of pink noise at 65 dB longer periods of use is unknown. Speech recognition SPL (± 6). Participants indicated the Localization speaker source for each . Results are reported as RMS error. Testing was conducted for each CI individually and bilaterally after 3 months of bilateral CI experience.

Litovsky RY, et al. Investigate speech 37 adults with Speech recognition: CNC words and HINT Speech recognition: The bilateral condition was Subjective reports from Simultaneous bilateral recognition abilities simultaneous bilateral sentences in quiet at 65 dB SPL. BKB-SIN significantly better than either unilateral condition participants as well as speech cochlear implantation of bilaterally Nucleus 24 Contour as described above in Litovsky et al. 2004. at all post-implant test intervals for the CNC and at recognition results support in adults: a multicenter implanted adults cochlear implants Questionnaire: At the 3 month post-implant all except the 3 month interval for the HINT bilateral benefit for postlingually clinical study. with simultaneous from 11 CI centers in interval, participants underwent a 3 week sentences. In noise, the bilateral condition was deafened adults who are surgeries. the US. period of unilateral device use (better ear). better than either unilateral with average head implanted simultaneously. Ear Hear. 2006 shadow effects of 4.9 for noise-right and 6.3 for Dec;27(6):714-31. The APHAB was completed at the end of that unilateral experience and again at the 6 noise-left and average binaural squelch effects of Speech recognition month interval after returning to bilateral 1.9 for noise at either side. Questionnaire device use. Questionnaire: On average, participants scored All participants were tested after 1, 3, and 6 the bilateral condition significantly higher than the months of device use. unilateral for ease of communication, reverberant conditions, and background noise.

Muller J, et al. Investigate speech 9 adults with bilateral FMW words in quiet at 65 dB SPL. HSM All participants had higher speech scores in the Bilateral cochlear implantation can Speech understanding understanding in cochlear implants. 6 sentences at 65 dB SPL in noise (CCITT) at bilateral condition than with either ear in the provide improved speech in quiet and noise in quiet and noise in were implanted with +10 dB SNR. unilateral condition on at least one measure, and recognition in quiet and in noise. bilateral users of the bilaterally sequential surgeries most for all measures. Duration of deafness did not seem Med-El Combi 40/40+ implanted adults. (~ 1 – 4 yrs apart) and Average sentence understanding increased an to be a contraindication for cochlear implant 3 had both ears average of 31% with bilateral compared to a bilateral implantation for this small system. implanted during the unilateral CI ipsilateral to the noise, and 11% sample. same surgery. Ear Hear 2002; compared to a unilateral CI contralateral to the 23:198-206. noise. The average word recognition score increased 19% with bilateral CIs compared to a Speech recognition unilateral CI. All differences in average scores were significant.

3 Study Objectives Participants Methods Results Conclusions

Neuman AC, et al. Investigate the 8 adults (1 pre- 9 loudspeakers spaced along a 180º arc There were individual differences between Bilateral CIs provide significant Sound-direction effect of stimulus lingually deafened) using speech (“Where am I now?”) and pink participants. Most participants had better benefit related to horizontal plane identification with type (speech vs. with bilateral cochlear noise bursts at 70 dB SPL (± 3 dB). localization in the bilateral condition in terms of . Results with bilateral cochlear pink noise bursts) implants that had both Participants indicated the speaker source for more correct responses and less error for pink noise and speech did not implants. on horizontal plane ears implanted each sound. Results reported as RMS error. incorrect responses. Localization was better for differ, suggesting either is localization for simultaneously. All the centrally located speakers than for the ones at acceptable for localization testing. Ear Hear. 2007 adults with bilateral had 5-11 mos of the ends of the arc and was better in the bilateral Feb;28(1):73-82. cochlear implants. device use. condition (mean RMS = 29º) than either unilateral Localization condition (mean right RMS = 47º; mean left RMS = 54º). Results with pink noise and speech stimuli were similar.

Nopp P, et al. Investigate sound 20 adults (1 pre- 9 loudspeakers spaced along a 180º arc Bilateral implants had substantial and significant Sound localization was Sound localization in localization with lingually deafened) using bursts of CCITT noise at random benefit. All but two participants (with early onset substantially improved with bilateral users of Med- bilateral compared bilaterally implanted levels of 60, 70, or 80 dB SPL. Participants of deafness) substantially improved their sound bilateral CIs for these adults who El Combi 40/40+ to unilateral CIs. during adolescence or indicated the speaker source for each localization ability when using both implants were primarily postlingually cochlear implants. later. 3 had both ears sound. Results reported as mean deviation compared to either one alone. With bilateral CIs, deafened with short duration of implanted (d) between azimuth of presentation and average accuracy with which subjects can localize deafness before implantation. Ear Hear 2004; simultaneously and response. sounds improves more than 30 degrees. 25:205-14. The authors suggest that the others during Minimal bias is seen for participants in the bilateral individuals with early onset of Localization sequential surgeries condition whereas large bias is seen in the deafness may achieve better (~ 4 mos to 5.5 yrs unilateral condition toward the side of device use. bilateral benefit, if implanted at apart). All had at In addition, the judgments were more consistent younger ages and that additional least 1 month of with bilateral CIs. investigation is needed. bilateral CI experience.

4 Study Objectives Participants Methods Results Conclusions

Ramsden R, et al. Evaluate binaural 30 adults from 7 CI CUNY sentences & CNC words in quiet at Data is available for 29 participants. 27 patients Bilateral benefit, head shadow, Evaluation of benefit in speech clinics in the UK who 70 dB SPL. CUNY sentences at 70 dB SPL preferred sound quality w/ both CIs and use them squelch, and redundancy effects bilaterally implanted recognition while received sequentially with 8-talker babble at + 10 dB SNR pre-op both daily. were demonstrated for some adult subjects with the controlling for implanted CIs. and individually determined SNRs post-op. In quiet, no bilateral advantage was demonstrated participants but not all. Benefit Nucleus 24 cochlear binaural summation Participants had at Testing occurred pre-op and at 1 week, 3 compared to the 1st CI alone at 3 or 9 months. can be obtained by adding a 2nd implant system. for adults who have lest 9 mos of months, and 9 months post-activation. Performance with the 2nd CI was significantly CI for previously implanted adults, been successful unilateral CI Speech in noise: Speech was always from worse than the 1st for sentences and words. particularly in noise. Some Otol Neurotol 2005; with one implant experience, open-set participants with long periods of 26(5): 988-98. the front. Noise was from the front, 90º to With noise from the front, bilateral performance and receive a 2nd sentence the right, or 90º to the left. time between surgeries had Speech recognition implant. understanding & < 15 was significantly better than 1st CI performance at poorer 2nd ear performance and years of deafness in Half the participants were implanted in the 3 & 9 months. Comparison of the best unilateral limited bilateral benefit. the 2nd CI ear. 2nd ear upon enrollment in the study. The score to the bilateral score at 9 months indicates a other half were implanted 9 months later to significant redundancy effect. With noise toward allow for quality of life comparisons. The the 1st CI, bilateral scores were better than 1st CI results of the 2 groups are combined and the scores at 3 & 9 months. Group data did not show quality of life measures were not discussed. a significant head shadow or binaural squelch effect but 18 of 29 participants had a head shadow effect and 6 of 18 participants had binaural squelch benefit. With noise toward the 2nd CI, bilateral scores are better than 2nd CI scores at 3 & 9 months. Head shadow effects ere present at 3 & 9 months but no significant squelch effect for the group. 5 of 18 participants, however had binaural squelch benefit.

Ricketts T et al. Compare speech 16 bilateral implanted Speech was presented from the front and Bilateral implant condition was superior to better Results support previous studies Speech recognition for recognition in adults. 14 received noise from multiple sources around the ear unilateral by 3.3 dB for the adaptive SNR task, that indicate a bilateral advantage unilateral and bilateral multiple noise simultaneous listener (30º to 330º). Adaptive HINT with and 9% for the fixed SNR CST test. In addition, for speech recognition in noise implant modes in the sources for bilateral implants. The other 2 amplitude-normalized cafeteria noise bilateral performance improved with experience. 8 from multiple noise sources. The presence of and better had the 2nd surgery 7 presented at 60 dBA resulting in a SNR for of 10 had improvements (11-20%) on CST at the authors suggest the improvement uncorrelated noise unilateral and 14 months after 50% correct. Connected Speech Test (CST) retest interval. is due to the effects of binaural sources. conditions at 2 the 1st surgery. with passages presented at 70 dBA and a Performance in quiet and noise differed, even at summation and squelch. The different time +10 dB SNR using 5 uncorrelated babble the greatest SNRs and the most difficult SNR binaural advantage of ~ 10% over Ear Hear 2006;Dec periods post samples. the best unilateral condition 27(6):763-773. resulted in the largest bilateral advantage. implant, and to A subset of 10 participants was retested 9 continued to be present over time. Speech recognition assess the effect of months later on the CST at +10 dB SNR; 6 different SNRs on of these participants were tested at 4 SNRs speech recognition. (+20, +15, +10, +5).

5 Study Objectives Participants Methods Results Conclusions

Schleich P, et al. Investigate speech 21 German-speaking OLSA sentences in noise (continuous noise Significant improvement was observed in all Bilateral CI users benefit Head shadow, recognition in noise adults (1 prelingually matching the long-term speech spectrum) listening conditions but one (the squelch effect for significantly from head shadow, squelch, and for adults with deafened) with using an adaptive procedure resulting in a noise from the right side, probably due to the squelch, and summation effects, summation effects in bilateral cochlear bilateral cochlear SNR for 50% correct. Speech was relatively small number of subjects). which are known effects for bilateral users of the implants. implants. 3 had both presented from the front and noise was No correlation between any effects (head shadow, normal-hearing subjects. Med-El combi 40/40+ ears implanted during presented at 60 dB SPL from the front, 90º squelch, summation) and duration of deafness of cochlear implant. the same surgery and right, or 90º left. first and second deafened ear, average duration of the others implanted Ear Hear 2004; deafness across ears, or theses factors expressed during sequential as a fraction of age. 25:197-204. surgeries (4 mos to Speech recognition 5.5 yrs between surgeries). All had at least 1 month bilateral experience.

Schoen F, et al. Investigate speech 9 adults with bilateral HSM sentences at 70 dB SPL in quiet and at Speech recognition increased with increasing Bilaterally implanted adults Speech reception recognition in noise CIs, implanted either 5 SNRs (+20 to 0 dB), performed in a 4 SNRs. All participants showed substantial gain in showed a substantial and thresholds obtained in for adults with sequentially (n=6) or loudspeaker setup (45º, 135º, 225º, 315º) to SNRs (approximately 4 dB on average; ranging statically significant bilateral a symmetrical four- bilateral CIs. simultaneously (n=3). eliminate any head shadow effect. Speech from 1.3 – 6.6 dB) that remained essentially stable benefit over performance with the loudspeaker was presented from the two speakers over time. better hearing ear. Bilateral CI arrangement from toward the better CI and noise from the two The bilateral advantage was evident shortly after users can process speech bilateral users of Med- speakers toward the poorer CI. Results are implantation of the second CI and did not require binaurally and take advantage of El cochlear implants. reported in change of SNR for 50% correct lengthy experience. binaural effects in addition to the for the bilateral condition compared to head shadow effect. Otol Neurotol 2002; unilateral. 23:710-4.

Speech recognition

Seeber BU & Fastl H. Evaluate the 2 bilaterally implanted Localization was conducted in a darkened Both subjects were able to localize stimuli that ILDs were the primary cues used Localization cues with contribution of CI recipients who had anechoic chamber with an 11 loud speaker differed in spectral and temporal structure. for localization with only minor bilateral cochlear binaural cues to very good horizontal array spaced along a 100º arc (although the Placement of speech processors above the head contribution from ITDs. This is in implants. localization using localization abilities. listener was able to select a source location (w/o head block) resulted in left – right contrast to NH listeners who rely variations of along a 140º arc). Stimuli were presented at discrimination whereas, placing a piece of primarily on ITDs. Because of J Acoust Soc Am. spectral and roving levels from 61 – 69 dB SPL. The this, the authors predict that, 2008 cardboard between the processors improved temporal content in participant indicated the source for each localization. although the subjects were very Feb;123(2):1030-42. stimuli, a modified sound using a computer-controlled laser good at localizing in this controlled Localization placement of CI pointer to allow 2º accuracy. Even when ITDs were artificially emphasized, test environment, their ability localization was more dependent on ILDs. processor Results with various noise types were would deteriorate in situations microphones, and compared as were the results with pulsed with multiple sounds where the altered head wide-band noise (WBN) for 2 microphone ILD cues may be unreliable. related transfer placements, and for WBN for stimuli with ILD functions to offset and ITD shifts. ITDs or ILDs.

6 Study Objectives Participants Methods Results Conclusions

Senn P, et al. Assess the minimal 5 participants with Speech recognition: HSM sentences Speech recognition: Percentage of correctly All patients benefited substantially Minimum audible audible angle sequentially implanted presented at 70 dB SPL in CCITT noise at understood words was significantly higher using from bilateral CI for speech angle, just noticeable (MAA) in NH adults bilateral CIs (2 individually set SNRs. Speech was bilateral CI than only CI ipsilateral to noise recognition in noise as the result interaural differences and bilateral CI prelingually deafened presented from the front and noise from the sources. Average increase of 33% (range 1-51%) of a head shadow effect. Binaural and speech recipients and teens and 3 front, 90º right, or 90º left. on the left and 56% (range 37-78%) on the right, squelch and summation effects intelligibility with assess speech postlinguistically Localization: A MAA task using 4 reference consistent with head shadow effect, were were seen in some but not all bilateral cochlear recognition in deafened adults). 5 points for teens and 8 for adults - equally observed. participants. Left-right implants using clinical bilaterally participants with NH spaced in a circle around the participant. Localization: The MAAs in the bilateral condition discrimination was at near normal speech processors. implanted adults. who were matched for White noise bursts were presented from the (3-8º) were significantly smaller than in either MAA values but front-back age. reference position and then from a unilateral condition and only slightly higher than discrimination was poor. The 2nd Audiol Neurotol 2005; CI performance lagged behind the 10:342-52 loudspeaker on a boom that allowed any those of normal hearing controls when the angle 45º or less. Participants were asked reference point was at 0º (left-right discrimination). 1st, suggesting earlier Speech recognition to indicate the direction the sound moved Front-back discrimination when the reference was implantation of the 2nd side might Localization (right/left or front/back). on either side, was poor. be more beneficial.

Tyler RS, et al. Evaluate speech 9 adults with bilateral Speech recognition: CNC words and CUNY Speech recognition: In quiet, statistically All subjects prefer using both CIs. Three-month results recognition and cochlear implants, sentences in quiet and CUNY sentences in significant binaural advantages observed for Results suggest that binaural with bilateral cochlear localization in implanted noise. Speech was presented at 70 dB SPL sentences in 5 participants and words for 2 benefits can be obtained, even implants. adults receiving simultaneously. from the front and noise at individually participants. For speech in noise, 4/9 had with two different processors. bilateral CIs after 3 determined SNRs from 90º to the right or significant improvement with noise from the front, Future studies will include more Ear Hear 2002; 23(1 months experience. left. 1/9 with noise from the left, 3/9 with noise from the Suppl):80S-89S. realistic localization and speech Localization: 2 speaker set up at 45º to the right. All participants showed a significant recognition measures. Speech recognition right and left. Bursts of noise were advantage of binaural versus monaural hearing for Localization presented randomly at 70 dB SPL (± 5 dB). at least one of the 4 speech perception measures. Participants were asked to indicate whether Localization: 6 of 7 participants tested had a the sound was from the right or left speaker. binaural advantage with localization significantly better in the bilateral condition than either unilateral condition.

Tyler RS, et al. Investigate 7 sequentially Speech recognition: Speech material Speech recognition: Testing in quiet indicated ear Individuals can benefit from Speech perception localization and implanted adults (6y presented at 70 dB SPL. CNC words in quiet differences for 4 of the participants whereas ear bilateral implantation even if there and localization with speech recognition 8m to 17y between & CUNY sentences at individually differences were present for all participants when are long periods of time between adults with bilateral abilities for a surgeries). Devices determined SNR using MTB. 4 participants tested in noise. All 4 participants tested for surgeries, the processing sequential cochlear diverse group of varied across were tested with the noise from each side to binaural squelch demonstrated significant binaural strategies are dissimilar, or the implants. bilateral implant participants and 3 determine the presence of binaural squelch. squelch for at least one side. recipients have pre- or post- recipients. individuals had All were tested with speech front and noise Localization: The 2 participants tested in the linguistic onset of deafness. Ear Hear. 2007 different devices for front. Apr;28(2 Suppl):86S unilateral condition prior to 2nd side implantation each ear. Duration of Localization: 8 loudspeaker array spaced demonstrated improvement in localization with Speech recognition bilateral device use along a 180º arc. 2 participants were tested bilateral device use. For the 7 participants, RMS Localization ranged from 2 mos to in the unilateral condition prior to 2nd side values ranged from about 12º to about 45º in the 6 yrs. implantation. All were tested in the bilateral bilateral condition (chance = 46 º). condition.

7 Study Objectives Participants Methods Results Conclusions van Hoesel RJ et al. Investigate bilateral One bilaterally Speech recognition: Sentences similar to Speech recognition: Bilateral improvements due Although ITD cues are not well Sound direction benefits using implanted patient who CUNY sentences presented at 70 dB SPL in to head shadow effects but not for binaural perceived with bilateral cochlear identification, measures of ITD received CIs in both multi-talker babble at an individually squelch. There was no effect of low and high rate implants, there is improved interaural time delay sensitivity, ears during a single determined SNR. Speech was presented update strategies in the test conditions. localization and speech discrimination, and localization, and surgery. from the front and noise from front, 90º right, Localization: At 70 dB SPL, mean absolute errors understanding in noise. These speech intelligibility speech recognition and 90º left. Low and high update rate were 81° and 73° for LE and RE, and 16° for benefits can be an advantage in advantages in noise in noise. strategies were evaluated. bilateral implants. At 60 dB SPL (no AGC), the every day communication for for a bilateral cochlear Localization: 11 loudspeaker array spaced mean error in the bilateral condition improved to cochlear implant recipients. implant user. along a 180º arc. Pink noise bursts were 8°. Ear Hear. 2002 presented at 70 & 60 dB SPL (± 3 dB). The Psychophysics: Best ITD JND was 350-400 µsec Apr;23(2):137-149. participant indicated the speaker source for for low rate pulse trains. Increased rates resulted each sound and results were reported in in larger JNDs. Speech recognition mean absolute errors. Localization Psychophysics Psychophysics: ITD JNDs were measured with a 3 AFC design with 70% accuracy. Stimuli were pulse trains using low rates and high rates modulated at 100 Hz presented to 2 matched bilateral place pairs of electrodes. van Hoesel RJ & Tyler Assess localization 5 bilateral Speech recognition: BKB sentences in Speech recognition: When speech and noise Bilateral implantation provides RS and speech simultaneously noise (BBN) using an adaptive procedure were both from the front, the bilateral score was improvement for localization and Speech perception, recognition in implanted participants resulting in a SNR for 50% correct. Speech similar to the best unilateral score. There were listening in noise when the sound localization, and bilateral and with a minimum of 1 was presented from the front at 65 dB SPL, significant improvements when speech and noise source and speech are spatially lateralization with unilateral year CI experience. and noise from the front, 90º from the right, were spatially separated due to head shadow separated, primarily due to head bilateral cochlear conditions; and 90º from the left. effects. Bilateral scores compared to the shadow effects. Psychophysical implants. evaluate the effects Localization: 8 loudspeaker array spaced shadowed ear (binaural squelch) indicated a 1-2 experiments indicate good of varied ITD and dB difference that was marginally significant. sensitivity to ILDs. ITD cues rely J Acoust Soc Am. along a 108° arc. Pink noise bursts at 65 dB ILD cues with direct SPL (±4 dB). The participant indicated the Localization: Averaged RMS errors were smaller on the availability of low rate 2003 Mar;113(3): electrical information below a few hundred 1617-1630. speaker source for each sound and results (10°) for bilateral conditions than for unilateral stimulation. were reported as RMS errors. conditions (20-60°) ; chance = 50%. Results were Hz. Speech recognition A new processing strategy designed to comparable with the clinical or research Localization processors. Psychophysics better preserve ITD cues (referred to as PDT, or peak derived timing) was used in Psychophysics: Good sensitivity for ILDs that was addition to the clinical strategy for better than 1dB for some participants. ITD localization testing. sensitivity was moderate, around 100 µsec, and Psychophysics: Participants made left-right decreased for stimuli with rates above a few judgments relative to a reference and hundred Hz using unmodulated pulse trains. absolute lateral position decisions as ILDs and ITDs were adjusted on place matched and loudness balanced electrodes from the two sides.

8 Study Objectives Participants Methods Results Conclusions van Hoesel RJ Assess 1) effect of One to two bilateral Exp 1: ITD JNDs for pulse trains as a Exp 1: Small place differences did not Data support previous findings Exploring the benefits place-matching on adult implant function of place of stimulation at a substantially change ITD sensitivity and JND that in bilateral implant users, ILD of bilateral cochlear ITD sensitivity; 2) recipients per comfortably loud level using a medial scores were within 2x as large when place varied cues are primarily used for implants. binaural loudness experiment. electrode for the LE and a range of by 3-4 mm and within 3x as large when place localization and speech summation for electrodes for the RE. varied by 7-8 mm. recognition in noise rather than Audiol Neurotol. broadband stimuli; ITD cues. The inability of current 2004;9:234-246. Exp 2: Loudness estimation with broadband Exp 2: Bilateral stimulation resulted in mean 3) signal detection pink noise bursts. 10 electrodes from each loudness values 1.8 times greater than unilateral cochlear implant devices to code Psychophysics in noise; and 4) side were loudness balanced for each ear as conditions and was a factor of 2 across most fine timing information at high Localization effects of array well as between ears near threshold and presentation levels (e.g. bursts were twice as loud rates may impede access to ITD span, signal maximal comfort levels. Noise bursts were when presented bilaterally). cues used in the normal hearing characteristics, system. presented across a 32 dB range for LE, RE, Exp 3: BMLDs in two subjects were considerably loudspeaker and bilateral. location, and sound lower than what would be expected with NH processing Exp 3: Measures of binaural masking level subjects suggesting minimal binaural speech strategy. differences (BMLD) with 500 Hz pulsed unmasking to be expected from the CI tones (in & out of phase at right/left participants. processor inputs) separated by 0.5-1.5s Exp 4: Adding low rate ITD cues may improve periods of silence and NBN centered at 500 localization performance for wider array spans; in Hz. Participants adjusted the level of the the lateralization task, ITD sensitivity was better tone until the on/off gating was detectable. for click trains than pink noise. Exp 4: Localization measures with 8 loudspeakers spaced along a 180º arc using pulsed pink noise and 50-Hz click trains at roved levels (60-68 dB SPL). Lateralization measures with direct routing into audio input of the speech processor. van Hoesel RJ Investigate various 3 bilaterally implanted Data were collected over a 4-12 month time Individual subject differences were present To date, electrical stimuli are not Sensitivity to binaural ways that electrical adults who were fairly period for each participant. however in general, higher pulse rates, lower able to transmit timing cues that timing in bilateral stimulation might good at identifying Several experiments were conducted to 1) stimulation levels, and shorter durations resulted are available to NH listeners. The cochlear implant provide binaural ITD sensitivity at a evaluate ITD sensitivity with various pulse in higher ITD thresholds. authors suggest this may be due users. timing cues and low rate (100 pps). rates, stimulus levels and durations; 2) Subjects perceived time-varying ITD cues at 100 to issues related to synchrony, their perception in refractory patterns, effects of J Acoust Soc Am. investigate time-varying ITDs rather than pps but could not at 300 pps. implant recipients. static ITDs and determine if subjects deafness and distorted place-rate 2007 Poor ITD discrimination was found on the second relationships. Apr;121(4):2192-206. perceive beats with higher pulse rates, and pulse of a two-pulse stimulus when the gap 3) assess sensitivity to later cues in the ITD cues may be more easily Psychophysics between the two pulses was a few milliseconds in signal compared to the onset. duration. identified with the use of a fine- timing based strategy than envelope based strategies, however channel interaction issues may limit practical benefits.

9 Study Objectives Participants Methods Results Conclusions

Verschuur CA, et al. Study localization 20 bilaterally Localization testing was conducted with 11 Marked improvement in horizontal sound Bilateral CIs are able to provide Auditory localization by bilateral CI implanted adults loudspeakers spaced along a 180º arc using localization with bilateral compared to unilateral CI significantly improved localization abilities in bilateral recipients and recruited from UK a variety of stimuli (speech, speech + and dual microphones. Small variation in bilateral over unilateral CIs. All cochlear implant investigate the multicenter CI trial. reverberation, pulsed pink noise, white noise performance; modest differences in localization participants demonstrated benefit recipients. effectiveness of w/simulated reverberation, tone bursts), performance for different stimuli. Performance with all stimuli types. Dual dual microphones most at 60 dB SPL, but also pulsed pink differences associated with level were relatively microphones provided no Otol Neurotol 2005; with one implant to noise at 70 dB SPL in order to activate the small and confined to unilateral conditions. localization benefit. 26:965-71. improve AGC of the speech processors. Results Bilateral localization benefit was consistent for a Localization localization. were reported as mean angular errors. range of stimuli with different temporal and Testing was conducted for each CI spectral characteristics and for all subjects. individually and bilaterally as well dual microphones providing input to the 1st CI.

Note: For all studies, testing was conducted with each device alone and also in the bilateral condition. APHAB = Abbreviated Profile of Hearing Aid Benefit; BKB = Bamford-Knowal-Bench; CCITT = Comite Consultatif Internationale de Telegraphie et Telephonie (International Telephone and Telegraph Consultative Committee); CI = cochlear implant; CIS = Continuous Interleaved Sampling; CNC = Consonant-Nucleus-Consonant; CUNY = City University of New York; dB = decibels; FMW = Freiburber Monosyllabic Words; HMS = Hochmair-Schultz-Mozer sentences; ILD = Interaural Level Difference; ITD = Interaural Time Difference; JND = just noticeable difference; OLSA = Oldenburger sentences; pps = pulses per second; PW = pulse width; RMS = root mean square; SNR = signal-to- noise ratio; SPL = sound pressure level.

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