Music and Cochlear Implants
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AUDIOLOGY FEATURE Music and Cochlear Implants BY GEOFF PLANT Introduction been restricted to envelope cues, and A number of studies have found that The introduction of multichannel many CI users have been frustrated while tempo and rhythm are relatively cochlear implants (CIs) in the early in their desire to listen to, and enjoy well perceived by CI users [10, 11], the 1980s provided children and adults music. The introduction of new latter two elements are not [3, 10, 11, with severe and profound hearing coding strategies, that allow at least 12]. For example, several studies have losses with greatly improved speech partial access to fine time structure, reported that CI users perform poorly perception skills. In this paper, has resulted in improved subjective on pitch perception tasks. Gfeller et al. however, I am going to focus on ratings of music by adult CI users [12] found that while normal hearing an area that continues to present [6, 7, 8], but these innovations are subjects’ mean difference limen for difficulties for many adult CI users – not available to most CI users, and it pitch was 1.13 semitones, that of adult music listening. appears that around 50% of adult CI CI users was 7.56 semitones; more users continue to be at least partially than half an octave. Further, the Music and cochlear implants dissatisfied with the sound of music. performance of the CI subjects was Although adult CI users are usually It must be remembered, however, highly variable, ranging from one to 24 able to communicate effectively via that about half of adult CI users are, semitones. audition alone, at least in quiet, a again, at least partially, happy with Care needs to be taken in the sizable proportion of this group report the sound of music. In my work, I have interpretation of these results, and in that they are disappointed with the tried to discover what can be done to determining their relevance for music sound of music. Lassaletta et al’s try to enrich the music experiences of listening by CI users. Although pitch (2007) study of the music listening all adults with a CI. There is much to is undoubtedly an important part of habits of adults, for example, found learn from those who are successful, most musical experiences, it is not that, although around 50% reported and I will attempt to explain what we necessarily an essential prerequisite that they enjoyed listening to music can learn from the experiences of this for music enjoyment. I know many CI with their CIs, the experience was group. users who report that they have great not as enjoyable as it had been difficulty following a tune, but still before implantation [1]. This finding Access to the components enjoy listening to music. is in agreement with earlier studies of music A more ‘valid’ measure of a CI user’s conducted by Gfeller and her Studies looking at the musical skills ability to access music might be the colleagues [2, 3], which found that of CI users often break music down recognition of familiar tunes. Gfeller around 50% of adult CI users reported into its constituent ‘elements’ such as et al. presented 49 adult CI users with at least some satisfaction with music tempo and rhythm, pitch interval and 12 ‘familiar melodies’, such as ‘Happy listening, while the remaining 50% melody, and timbre and instruments Birthday’, and ‘The Wedding March’ did not. [9]. Although this approach is rather played on a synthesised piano [12]. This is, perhaps, not surprising; CIs artificial, it does provide some useful The mean score for CI users was only were designed to give users access insights into why many CI users are 12.6% correct (range 0 – 43.75%), to speech, not music, and processing unhappy with music. which was significantly poorer than strategies have focused primarily that obtained by a control group of on the speech signal. Hilbert (1912) normal hearing adults (mean = 55.1%; showed that an acoustic signal can range = 13 – 68.9%). be decomposed into a slowly varying “CIs were designed to Although previous research had envelope (amplitude modulation) indicated that “experienced implant and a high-frequency carrier of give users access to recipients preferred the tone quality constant amplitude – the temporal speech, not music, and of the piano to that of seven other fine structure of the signal [4]. The commonly heard instruments” [12], it work of Smith et al. (2002) revealed processing strategies should be remembered that CIs were that fine time structure is critical have focused primarily developed specifically for speech, for music perception, while speech not music, and a ‘fairer’ test of the is relatively well transmitted by the on the speech signal.” ability of CI users to identify tunes more slowly changing temporal should perhaps use the human voice envelope structure [5]. Until relatively rather than a musical instrument. recently, the information from CIs has The obvious limitation of this ent and audiology news | MARCH/APRIL 2014 | VOL 23 NO 1 | www.entandaudiologynews.com AUDIOLOGY FEATURE approach, however, is that listeners “The CI user may be Getting back to music could use the lyrics to identify the Clinicians working with adult CI users song. One alternative is to substitute able to ‘evoke’ similar are often asked for advice on music the nonsense syllable [da] for each listening. The following suggestions syllable / note in a song or tune musical memories of a might be helpful for CI users who want to determine whether this led to familiar tune or song.” to get back to music listening. improvements in the ability of CI users • At first, restrict music listening to to identify familiar tunes. familiar songs. If possible, obtain I recorded 15 familiar songs, such a copy of the lyrics of the song, as as ‘Happy Birthday’, ‘Twinkle, Twinkle this can help reduce the complexity Little Star’ and ‘Yankee Doodle’, using of the task. this technique, and asked 15 adult seen as a multifaceted experience • Male singers, especially those with CI users to tell me the name of each that combines tempo and rhythm, lower registers (bass, baritone) piece [13]. The mean score for the pitch interval and melody, and timbre offer the best chance to detect subject group was 62% correct (range and instruments. It should also be atleast some pitch cues. = 20 – 100%), which is considerably noted that access to even one of • Look for ‘simple’ music. That higher than that reported by Gfeller these musical parameters may help is, music that has only one et al. [12]. There are several factors recognition of another. Gfeller et al., singer, because harmonies can that may have contributed to these for example, cite the case of a CI user create problems at first, and simple scores, such as access to temporal who “stated that she often listened to instrumentation. I often play cues, but the use of a male voice with the rhythmic pattern at the beginning Johnny Cash’s Walk the Line to my a relatively low pitch is probably the of an item. As the item continued, she clients, and almost all respond very most important. Oxenham (2005) would then try to match that pattern positively to this recording. It has believes that envelope cues presented with her memory of familiar melodies” a simple tune that is familiar by CIs can provide access to “single- [12]. to many adults, and Cash sings line melodies … within a limited pitch in a range where the CI user has a range (up to about 300 Hz)” [14]. Familiarity breeds content chance to detect pitch changes. Zeng (2004) noted that “cochlear Kraemer et al. provide some insights The instrumentation is very sparse implants subjects … have a great into the processes that may be and does not compete with the deal of difficulty identifying timbres involved in this type of “remembered voice, and there is a well defined, associated with different musical listening” [16]. They played familiar simple rhythm. instruments” [9], and this obviously and unfamiliar songs and tunes to a • DVDs of live performance offer creates difficulties in music listening. group of normal hearing listeners, the chance to both hear and see Gfeller et al. [3] presented a group while monitoring brain activity using the performance. DVDs often have of 51 CI users with a forced-choice functional magnetic resonance captions / subtitles and this can task involving eight different musical imaging (fMRI). Short segments, help the client ‘follow’ the songs. instruments – trumpet, trombone, ranging from two to five seconds in • Live music performances in a flute, clarinet, saxophone, violin, cello duration, were extracted from the small venue may also be a good and piano. The mean identification musical pieces, and replaced with way to return to music listening, score obtained by the CI users was periods of silence. They found that especially if the CI user is familiar 47% correct, whereas a control group “familiar songs induced greater with the performer’s repertoire. of listeners with normal hearing had activations in auditory association • If the client is listening to recorded a mean score of around 90% for the areas than did silent gaps embedded music, s/he should try to do so in same task. in unknown songs,” and that “simply a quiet room, or consider the use Bradley (2010) presented a closed- muting short gaps of familiar music of direct input, thereby bypassing set “instrument” test contrasting was sufficient to trigger auditory the acoustic conditions of the trumpet, saxophone, piano, flute, imagery that indicates the obligatory listening environment. drums / tympani, tuba, guitar, violin / nature of this phenomenon. • The CI user should be encouraged strings, female vocal and male vocal, Corroborating this observation, all to devote some time to music each to ten adult CI users [15].