Music Enjoyment and Cochlear Implant Recipients: Overcoming Obstacles and Harnessing Capabilities
Kate Gfeller, Ph.D., is the Russell and Florence Day Professor of Liberal Arts and Sciences in the School of Music and the Department of Communication Sciences and Disorders at the University of Iowa. Gfeller is a member of the Iowa Cochlear Implant Clinical Research Team in the Department of Otolaryngology—Head and Neck Surgery at the University of Iowa Hospitals and Clinics. As a part of that multidisciplinary team, her research on music perception has been funded by the National Institutes of Health, the Office of Special Education and Rehabilitation, and the Department of Defense. For 30 years, she has worked as part of multidisciplinary teams in conducting basic and translational research and providing music therapy services for children and adults with hearing losses. She has investigated perception and enjoyment of music, with an emphasis on real-world complex sounds, as well as music-based programs for auditory skill development. This includes applications intended to promote more meaningful involvement in social and educational settings.
Cochlear implants (CIs), while remarkably effective in supporting spoken communication, are technically limited at conveying melody, harmony, and the rich and pleasing tone quality of music. In addition, deficits to the auditory system associated with hearing loss can have negative consequences for music listening. Despite these obstacles, many children who use CIs enjoy music, and some adult users have regained satisfying music experiences. This article summarizes research on technical, biological, and experiential factors that may limit music enjoyment; training or accommodations that have improved music perception and enjoyment; and practical approaches that CI users can use to harness their potential for music enjoyment.
“ Music sounds like a cage full of squawking parrots.”
“ The organ at church sounds like a train comingthrough the sanctuary.”
“ I can hear the music, but it doesn’t make sense to me.”
These are a few quotes from cochlear implant (CI) recipients, describing how music sounds through their CIs. Their comments highlight some of the obstacles that CI users face when using a hearing device designed primarily to support spoken communication. CIs are remarkably effective in conveying the salient features of speech, particularly in quiet listening environments. However, they are not well suited for conveying melodies, harmonies, and the beautiful tone qualities that people with typical hearing associate with music (Looi, Gfeller, & Driscoll, 2012). Because music is pervasive in most cultures (e.g., part of social events, religious services, etc.), CI users are likely to be exposed to music on a daily basis (e.g., Cross, 2004; Gfeller, 2008). Furthermore, music is associated with cultural and personal expression and emotional wellbeing; thus, the extent to which CI recipients are able to perceive and enjoy music has relevance to social integration and quality of life (Gfeller & Knutson, 2003).
This article describes music’s salient characteristics; technical, biological, and experiential factors that undermine or support music perception; training to enhance music perception and enjoyment; and practical recommendations for optimizing music listening and enjoyment.
Structural Components of Music
When listening to music, we perceive complex and rapidly changing combinations of pitch, timbre, rhythm, and loudness (Looi et al., 2012). Rhythm, sometimes referred to as temporal patterns, is the sequential duration of notes. These temporal patterns comprise melodic rhythms (long and short notes in melodies), underlying beat (e.g., triple meter in waltzes), and tempo (e.g., fast, slow). Loudness is the aspect of the acoustic signal associated with amplitude, or magnitude, of auditory sensation. In music, a wide and rapidly varying dynamic range (from barely audible to bombastically loud) is considered an important expressive element.
Pitch, how high or low a note sounds, forms the basis of melodies (sequential pitch patterns) and harmony (concurrently presented pitches) (Looi et al., 2012). Timbre refers to the distribution of spectral energy that helps a listener differentiate musical instruments or singers performing the same pitch. For example, Bob Dylan’s voice is unmistakable because of its nasal quality. Trumpets are sometimes described as sounding brilliant, while clarinets have a hollow sound. Timbre not only helps listeners to identify who or which instrument they are hearing, but also contributes to the aesthetic beauty or entertainment value of music. Perceptual requirements for both pitch and timbre include adequate representation of spectrally complex aspects of the acoustical signal (sometimes referred to as the fine structure) (Limb & Roy, 2014).
In real-world music, the attributes of pitch, timbre, rhythm, and loudness are typically organized in rapidly changing combinations. The listener engages in simultaneous perceptual processing of multiple input sources (e.g., groups of instruments playing many concurrent melodic and rhythmic patterns) (Looi et al., 2012). The following section will describe how effective the CI is in conveying these building blocks of music.
Cochlear Implants and Music Perception
Cochlear implants do not transmit a faithful representation of musical sounds. Rather, current generation implants usually remove the fine structure information in the sound waves and preserve the broad features of the temporal envelopes (Kong, Cruz, Jones, & Zeng, 2004; Kong, Stickney, & Zeng, 2005). In other words, CIs are most effective in conveying durational information, such as rhythm and tempo (Looi et al., 2012; McDermott, 2004).
In musically relevant rhythmic tasks, many CI recipients have similar accuracy as listeners with typical hearing. This includes discrimination of tempo (e.g., slow or fast), meter (e.g., duple or triple), and simple rhythm patterns (e.g., reviews in Limb & Roy, 2014; Looi et al., 2012; McDermott, 2004). In functional terms, this means that CI users have similar capabilities as persons with typical hearing in tasks such as clapping or moving to a beat, or in playing percussion instruments (Hsiao & Gfeller, 2012). Research indicates that postlingually deafened CI users can use melodic rhythm to compensate for poor pitch perception in identifying familiar melodies (Gfeller, Turner, et al., 2002). Some CI users prefer compositions with prominent and clear rhythmic components over music emphasizing lyrical melodies and harmony (Au, Marozeau, Innes-Brown, Schubert, & Stevens, 2012). In summary, CI users can enhance their understanding and enjoyment of music by attending to its rhythmic elements.
Although CI users can ‘hear’ musical sounds fairly easily, they are likely to have a restricted dynamic range due to technical limitations of the device as well as damage to the auditory system. This results in more difficulty hearing extremely quiet sounds or tolerating very loud sounds, or processing rapid changes in dynamics (e.g., soft to loud) (Limb & Roy, 2014; Looi et al., 2012).
Pitch perception of CI users is significantly less accurate than that of listeners with typical hearing because of technical limitations of the CI as well as damage to the auditory system (e.g., Limb & Roy, 2014; Looi et al., 2012). On average, CI recipients are less accurate than listeners with typical hearing on detection of small pitch changes, determining if one pitch is higher or lower than another (pitch ranking), and pitch patterns recognition or discrimination (Gfeller et al., 2007; Kong et al., 2004; Looi et al., 2012). In functional terms, some CI recipients may hear no pitch change from one note to the next; others may perceive changes in pitch, but the size of pitch change may be compressed or distorted. The poor representation of pitch conveyed through the CI sheds light on comments quoted at the introduction of this paper, such as “I can hear the music, but it doesn’t make any sense.”
Interestingly, while some individuals who use CIs have improved pitch perception as a result of upgrades in signal processing, research from large groups of CI users reveals no statistically superior pitch perception for specific models of conventional internal arrays (22 mm electrode) or commercially available processing strategies (e.g., Gfeller et al., 2008; Gfeller, Jiang, Oleson, Driscoll, & Knutson, 2010; Gfeller, Turner, et al., 2010; Kong et al., 2004; Looi et al., 2012; McDermott, 2004). However, adult CI users who have sufficient residual hearing to benefit from well-fitted hearing aids worn with the CI (bimodal stimulation) have shown perception superior to CI use alone (Dorman, Gifford, Spahr, & McKarns, 2008; El Fata, James, Laborde, & Fraysse, 2009; Gfeller et al., 2008, 2010; Looi et al., 2012). Thus, well-fitted hearing aids worn with CIs can sometimes enhance music perception.
Because melodies and harmonies are made up of pitch patterns, it is not surprising that CI recipients are significantly less accurate than persons with typical hearing on perception of melodic and harmony patterns (e.g., for reviews, see Limb & Roy, 2014; Looi et al., 2012; McDermott, 2004). However, accuracy can be enhanced by contextual cues (e.g., watching the singer, melodies associated with special events such as “Happy Birthday”) (Olszewski, Gfeller, Froman, Stordahl, & Tomblin, 2005). This is illustrated by the following comment from a CI user: “It does help… if I know what it’s [i.e., music] supposed to sound like. For example, the ‘Star Spangled Banner’ started to sound fairly normal about a week into the Olympics, but I think this is my brain filling in the missing pieces.”
Perhaps the most challenging pitch-based task for many CI recipients is accurate production of pitch, such as singing in tune, or tuning an instrument. Objective testing of singing by groups of pediatric CI recipients (Nakata, Trehub, Mitani, & Kanda, 2006; Xu et al., 2009) indicates that most children with CIs are significantly less accurate than children with typical hearing in matching pitches and singing the melodic contour in tune.
Timbre allows the listener to differentiate between two instruments or singers playing/singing the same note at the same level of loudness (Looi et al., 2012). Timbral blend is the term used to describe multiple instruments or voices producing notes simultaneously. CI users are significantly less accurate than listeners with typical hearing in recognizing musical instruments by sound quality alone, though single musical instruments tend to be easier to identify than more complex blends (reviews in Limb & Roy, 2014; Looi et al., 2012; McDermott, 2004). However, CI signal processing provides sufficient spectral detail for the listener to detect differences in sound quality between two contrasting sound sources (e.g., detecting a difference between a flute and a piano).
In everyday life, listeners are seldom required to identify musical instruments. However, tone quality (e.g., brilliant, smooth, haunting, etc.) is an important part of music appreciation. The term appraisal is often used in research evaluating timbre on dimensions of pleasantness or specific characteristics (e.g., rough vs. smooth). As a group, CI recipients appraise the tone quality of musical instruments less pleasantly than do listeners with typical hearing (reviews in Looi et al., 2012; McDermott, 2004).
Differences Among CI Users
The previous paragraphs have focused on average, or typical, perceptual capabilities documented across groups of CI users (e.g., Looi et al., 2012; McDermott, 2004). Individual CI recipients, however, differ considerably on perception and appraisal of those aspects of music for which pitch and timbre are salient (Gfeller et al., 2008; Gfeller et al., 2010; Looi et al., 2012). Some, such as those quoted in the introduction of this paper, describe music as little more than obnoxious noise. However, others have remarkable levels of accuracy and enjoyment, despite the technical limitations of the CI. For example, one CI user from the Iowa Cochlear Implant Clinical Research Center, after adjusting to her device, described music with her CI this way: “I think those of us who were intimately connected to music before our hearing losses notice the little ways that music is part of the warp and woof of life and relish our recovery of something priceless.”
Interestingly, appraisal and enjoyment of music is not merely a function of perceptual accuracy (Gfeller et al., 2008; Gfeller, Witt, Spencer, Stordahl, & Tomblin, 1999; Wright & Uchanski, 2012). There are individuals who have above average perceptual acuity who nevertheless dislike music through the CI. In contrast, there are CI users with relatively poor acuity who truly enjoy music. Individual expectations can have an important impact upon music enjoyment (Gfeller, Mehr, & Witt, 2001). This comment from an adult who is postlingually deaf illustrates the importance of expectations in relation to music appreciation: “Initially it was very disappointing to listen to music with my CI. … I have had to adapt. [After] accepting a ‘new sound’ … it can be extremely enjoyable to listen to music now … it’s just different.”
In addition to expectations, other factors contribute to variable perception and enjoyment among CI users, including: residual hearing, hearing aid use, current age, how efficiently the brain processes incoming auditory information, onset of hearing loss, experiential circumstances, and musical training (Gfeller et al., 2008, 2010; Looi et al., 2012; McDermott, 2004). For example, implant recipients with greater damage to the auditory system may enjoy less benefit from enhanced signal processing strategies designed to convey greater fine structure (e.g., Fu, Shannon, & Wang, 1998) or from the acoustic stimulation presented via a hearing aid (bimodal hearing) (El Fata et al., 2009; Looi et al., 2012).
Younger CI users may have the advantage of greater neural plasticity, which contributes to more efficient use of new information (Gfeller, Driscoll, Kenworthy, & Van Voorst, 2011; Hsiao and Gfeller, 2012). CI users of all ages differ in how efficiently their brains discriminate and process sounds (Gfeller et al., 2008). Regarding onset of hearing loss, CI users who are postlingually deaf can use contextual cues (e.g., using memory of music) to support understanding (Gfeller et al., 2001). Postingually deafened CI users tend to appraise musical sound quality poorly in contrast with perceptions prior to hearing loss, while children whose entire experience with music has been through a CI may have less stringent expectations regarding what constitutes aesthetically pleasing music (Gfeller, Witt et al., 1999; Hsiao and Gfeller, 2012).
Music listening can also be influenced by environmental circumstances. For example, an overly reverberant room or poor sound equipment can make listening more difficult, while listening can be enhanced through visual cues such as watching the singer, or reading along with notation or song lyrics (Gfeller, Christ, et al., 2000; Gfeller et al., 2008, 2010).
In recent years, there has been growing interest in the impact of musical training. As noted previously, CI users are less accurate than persons with typical hearing on perception of pitch and timbre. However, significant perceptual improvements can occur as a result of systematic training (e.g., Driscoll, 2012; Fu & Galvin, 2007; Gfeller et al., 2011; Gfeller, Witt, Stordahl, Mehr, & Woodworth, 2000; Gfeller, Witt, et al., 2002; Rocca, 2012).
In addition to improved music perception and enjoyment (e.g.,melody recognition, sound quality ratings) studies with listeners with typical hearing indicate that music training may enhance the efficiency with which the auditory pathways process speech as
well as musical sounds. Researchers hypothesize that the heightened fine-grained frequency discrimination required to perceive music may, over time, improve perceptual skills that generalize to perception of more complex speech tasks, including vocal inflection, talker identification, and speech perception in noisy listening conditions (e.g., Chermak, 2010; Kraus & Skoe, 2009; Kraus, Skoe, Parbery-Clark, & Ashley, 2009; Shahin, 2011).
In our lab, we are currently comparing adults with typical hearing with either little (if any) or extensive musical training on their neural and behavioral responses to various musical stimuli. For example, preliminary data indicate that, those with extensive musical training have more accurate behavioral measures for pure tone pitch discrimination at 800 and 1600 Hz (Satterthwaite p-value, p < .05).
These observations with listeners with typical hearing from various centers, including our own, have prompted speculation that music training may benefit CI users, enhancing their extraction of finestructure information from complex aspects of speech and music. However, given the very atypical auditory signal conveyed by the CI, systematic evaluation of music training is required in order to better assess the potential benefit to CI recipients (Shahin, 2011). Our research center is one of several currently involved in examining the impact of musical training on auditory processing of CI users.
In summary, the CI is not ideally suited for conveying several structural attributes of music, although acuity and appraisal vary considerably among CI users. Furthermore, some aspects of music listening can be enhanced through accommodation or music
training. These research findings suggest practical strategies for CI users, which are noted on the following page.
Practical Strategies to Enhance Music Listening and Participation
Perhaps the most prudent advice one can offer regarding music and CIs is a balanced message: Music will not be the same as it was prior to implantation, but many people can improve through accommodation or focused practice over time. The word “music” encompasses complex and diverse structural combinations. Furthermore, perceptual and production requirements differ greatly, depending upon how one engages with music (e.g., listening, singing, playing an instrument). Thus, one solution will not fit all individuals or circumstances; trial and error will help determine which aspects of music are most enjoyable, or have potential for improvement. The personal priorities and motivation of each user and their family should be taken into account, given that improved music perception requires some dedicated effort over time.
A combination of training and accommodation can address different aspects of music engagement. Training (focused listening exercises) is geared toward improving neural efficiency and learning to associate particular sounds with specific musical entities. Accommodations are practical strategies intended to compensate for the technical limitations of the device (e.g., quiet listening environments or using visual cues) or the auditory system. The following list offers practical strategies for enhancing music perception and enjoyment for CI users (Gfeller et al., 2001).
Establish realistic expectations.
Listening. Music will not sound as it did prior to deafness and/or cochlear implantation, and one should avoid comparisons with “star” users. However, many pediatric CI users do enjoy some aspects of music (Gfeller et al., 1999) and many adult CI users have been able to reestablish listening enjoyment as long as new expectations are established. As is true for most listeners with typical hearing, CI users may discover that some musical experiences may be more enjoyable than others (Gfeller & Knutson, 2003).
Making music. Some pediatric and adult CI users have found greater satisfaction in playing instruments that do not require ongoing tuning (e.g., as is required for violin, guitar), and which provide visual and kinesthetic cues that supplement audition (e.g., the piano). In music instruction, it is important to remember that aural limitations for pitch perception are due in large measure to the characteristics of the CI, and do not reflect lack of effort or intelligence. Instructional goals and objectives should be individualized and reassessed periodically to reflect the individual’s current capabilities, as well as to identify realistic avenues for growth and development. Several sources in the references of this article provide more information regarding accommodations for music instruction (Gfeller et al., 2011; Gfeller et al., 2001; Hsiao & Gfeller, 2012).
Listen to music in an optimal environment.
Avoid extremely reverberant rooms or situations having many distractions.
Improve perceptual accuracy and sound quality through listening practice.
Change requires repeated exposure to musical sounds over time. Practice is likely to be more effective and less frustrating if completed when the listener is rested and alert, and in short rehearsals distributed over several days/weeks.
Begin by attending to those structural attributes that are most effectively transmitted through the CI.
For example, initially choose music activities for which rhythm is an important component (e.g., focusing on the rhythm while listening, moving to music). As skills increase, focus on more challenging tasks.
Use contextual cues.
These include watching the musician, reading the notation or song lyrics, or prior knowledge of the music to piece together the sounds.
Music perception is an important indicator of CI benefit, both with regard to social integration and quality of life. Although music as heard through a CI is not the same as typical hearing, through judicious choices and persistent practice, many CI users can achieve more satisfactory engagement with music in their daily lives. What’s more, enhanced music perception may have carryover to more effective navigation of the complex acoustic environment encountered in everyday life.
Portions of this paper were supported by grant 2 P50 DC00242 from the NIDCD, NIH; grant 1R01 DC000377 from the NIDCD, grant RR00059 from the General Clinical Research Centers Program, NCRR, NIH; and the Iowa Lions Foundation. Thanks are due to Virginia Driscoll for assistance in the preparation of this manuscript.
Au, A., Marozeau, J., Innes-Brown, H., Schubert, E., & Stevens, C. (2012). Music for the cochlear implant: Audience response to six commissioned compositions. Seminars in Hearing, 33(4), 335-345.
Chermak, G. (2010). Music and auditory training. The Hearing Journal, 63(4), 57-58.
Cross, I. (2004). Music, cognition, culture, and evolution. In I. Peretz & R. Zatorre (Eds.), The Cognitive Neuroscience of Music (pp. 42-56). Oxford, England: Oxford University Press.
Dorman, M. F., Gifford, R. H., Spahr, A. J., & McKarns, S. A. (2008). The benefits of combining acoustic and electric stimulation for the recognition of speech, voice, and melodies. Audiology and Neurotology, 13(2), 105-112.
Driscoll, V. (2012). The effects of training on recognition of musical instruments by adults with cochlear implants. Seminars in Hearing, 33(4), 410-418.
El Fata, F., James, C., Laborde, M., & Fraysse, B. (2009). How much residual hearing is ‘useful’ for music perception with cochlear implants? Audiology and Neurotology, 14, 14-21.
Fu, Q., & Galvin, J. (2007). Perceptual learning and auditory training in cochlear implant recipients. Trends in Amplification, 11(3), 193.
Fu, Q., Shannon, R. V., & Wang, X. (1998). Effects of noise and spectral resolution on vowel and consonant recognition: Acoustic and electric hearing. Journal of the Acoustical Society of America, 104, 3586-3596.
Gfeller, K. E. (2008). Music: A human phenomenon and therapeutic tool. In W. B. Davis, K. E. Gfeller & M. H. Thaut (Eds.), An Introduction to Music Therapy Theory and Practice. (3rd ed., pp. 41-75). Silver Spring, MD: American Music Therapy Association.
Gfeller, K. E., Christ, A., Knutson, J. F., Witt, S., Murray, K. T., & Tyler, R. S. (2000). Musical backgrounds, listening habits, and aesthetic enjoyment of adult cochlear implant recipients. Journal of the American Academy of Audiology, 11, 390-406.
Gfeller, K. E., Driscoll, V., Kenworthy, M., & Van Voorst, T. (2011). Music therapy for preschool cochlear implant recipients. Music Therapy Perspectives, 29(1), 39-49.
Gfeller, K. E., Jiang, D., Oleson, J., Driscoll, V., & Knutson, J. F. (2010). Temporal stability of music perception and appraisal scores of adult cochlear implant recipients. Journal of the American Academy of Audiology, 21(1), 28-34.
Gfeller, K. E., & Knutson, J. F. (2003). Music to the impaired or implanted ear: Psychosocial implications for aural rehabilitation. ASHA Leader, 8(8), 12-15.
Gfeller, K. E., Mehr, M., & Witt, S. (2001). Aural rehabilitation of music perception and enjoyment of adult cochlear implant users. Journal of the Academy for Rehabilitative Audiology, 34(17), 27.
Gfeller, K. E., Oleson, J., Knutson, J. F., Breheny, P., Driscoll, V., & Olszewski, C. (2008). Multivariate predictors of music perception and appraisal by adult cochlear implant users. Journal of the American Academy of Audiology, 19(2), 120-134.
Gfeller, K. E., Turner, C., Oleson, J., Kliethermes, S., & Driscoll, V. (2012). Accuracy of cochlear implant recipients on speech reception in background music. Annals of Otology, Rhinology & Laryngology, 121(12), 782-791.
Gfeller, K. E., Turner, C., Oleson, J., Zhang, X., Gantz, B., Froman, R., & Olszewski, C. (2007). Accuracy of cochlear implant recipients on pitch perception, melody recognition and speech reception in noise. Ear and Hearing, 28(3), 412.
Gfeller, K. E., Turner, C., Woodworth, G., Mehr, M., Fearn, R., Witt, S., & Stordahl, J. (2002). Recognition of familiar melodies by adult cochlear implant recipients and normal-hearing adults. Cochlear Implants International, 3, 31-55.
Gfeller, K. E., Witt, S., Adamek, M., Mehr, M., Rogers, J., Stordahl, J., & Ringgenberg, S. (2002). Effects of training on timbre recognition and appraisal by postlingually deafened cochlear implant recipients. Journal of the American Academy of Audiology, 13, 132-145.
Gfeller, K. E., Witt, S. A., Spencer, L., Stordahl, J., & Tomblin, J. B. (1999). Musical involvement and enjoyment of children using cochlear implants. The Volta Review, 100(4), 213-233.
Gfeller, K. E., Witt, S., Stordahl, J., Mehr, M., & Woodworth, G. (2000). The effects of training on melody recognition and appraisal by adult cochlear implant recipients. Journal of the Academy of Rehabilitative Audiology, 33, 115-138.
Hsiao, F., & Gfeller, K. E. (2012). Music perception of cochlear implant recipients with implications for music instruction: A review of literature. Update: Applications of Research in Music Education, 30, 5-10.
Kong, Y. Y., Cruz, R., Jones, J. A., & Zeng, F. G. (2004). Music perception with temporal cues in acoustic and electric hearing. Ear and Hearing, 25(2), 173-185.
Kong, Y. Y., Stickney, G. S., & Zeng, F. G. (2005). Speech and melody recognition in binaurally combined acoustic and electric hearing. Journal of the Acoustical Society of America, 117(pt. 1), 1351-1361.
Kraus, N., & Skoe, E. (2009). New directions: Cochlear implants. Annals of the New York Academy of Sciences, 1169(1), 516-517. doi:10.1111/j.1749- 6632.2009.04862.x
Kraus, N., Skoe, E., Parbery-Clark, A., & Ashley, R. (2009). Experience induced malleability in neural encoding of pitch, timbre, and timing. Annals of the New York Academy of Sciences, 1169, 543-557.
Limb, C., & Roy, A. T. (2014). Technological, biological, and acoustical constraints to music perception in cochlear implant users. Hearing Research, 308, 13-26.
Looi, V., Gfeller, K. E., & Driscoll, V. (2012). Music appreciation and training for cochlear implant recipients: A review. Seminars in Hearing, 33(4), 307-334.
McDermott, H. J. (2004). Music perception with cochlear implants: A review. Trends in Amplification, 8(2), 49-81.
Nakata, T., Trehub, S. E., Mitani, C., & Kanda, Y. (2006). Pitch and timing in the songs of deaf children with cochlear implants. Music Perception, 24(2), 147-154.
Olszewski, C., Gfeller, K. E., Froman, R., Stordahl, J., & Tomblin, B. (2005). Familiar melody recognition by children and adults using cochlear implants and normal hearing children. Cochlear Implants International, 6(3), 123-140.
Rocca, C. (2012). A different musical perspective: Improving outcomes in music through habilitation, education and training for children with CIs. Seminars in Hearing, 33(4), 425-433.
Shahin, A. J. (2011). Neurophysiological influence of musical training on speech perception. Frontiers in Psychology, 2(126). doi: 10.3389/fpsyg.2011.00126
Wright, R., & Uchanski, R. M. (2012). Music perception and appraisal: cochlear implant users and simulated cochlear implant listening. Journal of the American Academy of Audiology, 23, 350-365.
Xu, L., Zhou, N., Chen, X., Li, Y., Schultz, H. M., Zhao, X., & Han, D. (2009). Vocal singing by prelingually-deafened children with cochlear implants. Hearing Research, 255, 129-134.