Acommon experience of many patients following the initial activation of their cochlear implants (CI) is a confusing cacophony of the surrounding world. With time, the individual elements that make up the untellable mess of sounds start falling into place, becoming words, sobs, laughter, clanking plates, and other innumerable sounds of everyday life. For all CI users, this process is deeply emotional and, for many, highly challenging. Some quickly discover and rediscover new and old sounds every day, while for others, progress is much slower and more frustrating. Thus, our recent research focused on how to assess and improve the ability of CI users to identify sounds in everyday life in addition to speech and music.
Everyday sounds are rich with information about surrounding objects and events. Avoiding collisions while walking, knowing the direction of moving objects, and recognizing a person by his or her footsteps are some of the things that people with normal hearing do as they navigate their environment (Carello. In: Anderson & Anderson, eds. SIU Press, 2007 http://ow.ly/ha6u309S0ty). But most auditory processing of information about external sound-producing events happens below the threshold of awareness. Thus, these important aspects of auditory perception are easily overlooked unless examined explicitly.
CI USER EXPERIENCE
A blind CI user once shared how his CI enabled him to better judge if a hallway door was open or closed as he passes by and taps the floor with a cane. While the subtle acoustic cues required for this intricate task may be available to some sighted CI users and people with normal hearing, only a few are aware of these cues unless explicitly prompted to perform a similar task (WIREs. 2016;7:382 http://ow.ly/artC309LjJy). An auditory perceptual dimension is inherent in many aspects of life that are not commonly considered sound-related. Research has indicated that “nonauditory” experiences like enjoying a beverage can be affected by the sound of opening its container, while avoiding a spill when pouring water into a cup can be aided through listening (Flavour. 2015;4:1 http://bit.ly/2mAz5dl; J. Exp. Psychol. 2000;26:313 http://ow.ly/Zshy309LkNW). Hearing loss also appears to affect the strength of emotional response to sounds in one's environment, which may be reflected in neural processing differences of emotional sounds (JSLHR. 2016;59:1233 http://ow.ly/1Lib309Ll1X; Front. Syst. Neurosci. 2014;8:10 http://ow.ly/NrPa309Lm1M).
Notably, aspects of perceived body image, especially in relation to motor coordination and multisensory integration when learning new tasks, may be related to hearing abilities (Neural Plast. 2016;2016:5260671 http://ow.ly/D4M1309Llz2). Judgments of whether one can reach a small, moving, and sound-producing object that is out of sight, such as a pencil rolling off the desk, appear to be scaled to one's body size. In one experiment, blindfolded but otherwise sighted people with normal hearing were able to determine if they would be able to fit through an opening between themselves and an arbitrary sound source on the other side of the hallway (Ecol Psychol. 1999;11:175 http://ow.ly/qCRZ309LmJo). The decision of whether the opening was wide enough was associated with the shoulder width of the participants. Thus, in addition to signaling important safety information such as fire alarms, common environmental sounds contribute significantly to other less obvious aspects of a person's life and well-being.
ENVIRONMENTAL SOUND AWARENESS
One surprising finding that has emerged from recent research is that experienced CI users, even those with reasonably high speech perception scores, generally demonstrate mediocre abilities in identifying common environmental sounds. Whereas normal hearing peers identify many of such sounds with nearly 90-100 percent accuracy, adult CI users tested with the same environmental sounds, on average, score between 45-79 percent correct across studies (JSLHR. 2015;58:509 http://bit.ly/2ownPn2). Notably, CI users are often unaware of this perceptual deficit until tested. Few CI users present with specific complaints about environmental sound perception, often resulting in a misleading sense among clinicians and researchers that environmental sound awareness is not an important area of concern for CI users. In fact, the more accurate conclusion is that they do not know what they are missing.
Recently, we developed a Familiar Environmental Sound Test (FEST) to assess environmental sound awareness in diverse listening populations. This brief measure was specifically designed to meet time constraints of clinical testing (PLOS ONE. 2016;11:e0167030 http://ow.ly/UnDd309LmWQ). The first part of the test, FEST-I (for Identification), examines the ability of a listener to identify individual environmental sounds presented in quiet. This test includes 25 environmental sounds representing a broad sampling of familiar sounds encountered in everyday life. Middle- to older-aged adults with normal hearing tested in this part of the study were able to name these environmental sounds with 91.3 percent accuracy, while their peers with mild to moderate hearing loss scored 83.3 percent on average. In contrast, results from an ongoing study showed that 25 adult CI users of similar age range scored only 63.8 percent when tested with the same sounds.
Moreover, in line with our previous work, strong and significant correlations were observed between the environmental sound identification scores of the same group of 25 adult CI users and their scores on several speech tests (Fig. 1). Notably, the correlations between environmental sounds and speech scores only decreased slightly when the variance due to age, severity of hearing loss, spectral processing, and cognitive abilities were controlled. This suggests that the association between identification of environmental sounds and recognition of speech is not primarily driven by limiting factors inherent in individual audiologic and general cognitive abilities, or by limitations in implant processing that affect both classes of sounds. Rather, this association may reflect the more specific ability to process acoustically complex and semantically meaningful information or features shared by speech and environmental sounds.
The second part of the FEST test, FEST-S (for Sequence), presents listeners with 10 sequences of five environmental sounds each, drawn from the same set of 25 individual sounds. In five of the 10 sequences, individual sounds are semantically “coherent” with each other, denoting semantically related events that may happen in close temporal proximity in everyday life (e.g., alarm clock, followed by a yawn, then chirping birds). In the other five sequences, the same 25 sounds are presented in an “incoherent” fashion with no easily discernible semantic theme (e.g., a sound of waves followed by chainsaw and a squeaking toy). FEST-S places increasing demands on the listeners’ working memory and ability to use contextual information to improve performance.
Previous testing using FEST-S with eight CI users indicated that like older adults with normal hearing or mild to moderate hearing loss, CI users could effectively utilize the semantic context provided by the sounds in a sequence (PLOS ONE. 2016 http://ow.ly/UnDd309LmWQ). Following a brief training wherein listeners received feedback and could replay missed sounds, identification accuracy increased from 73 to 85 percent on average. These CI users were then able to place individual sounds in the correct order with an accuracy rate of 56.5 percent for coherent and 33.5 percent for incoherent sequences. This performance is comparable to that of both older normal hearing (55.2% and 40.9%, respectively) and older hearing impaired listeners (50.9% and 37.8%, respectively; Fig. 2). It also suggests the possibility of generalizable benefits following even a brief sound identification training with individual sounds.
Previous studies, though still limited in number and scope, consistently indicated that improvements in performance due to environmental sound training can extend to environmental sounds other than those used during training and potentially to speech (JSLHR. 2015 http://bit.ly/2ownPn2). Our previous environmental sound training study with CI patients, which consisted of four training sessions of up to one hour each, also revealed a trend toward better speech intelligibility. Although the change in speech scores was not significant, it is possible that speech perception will continue to improve in a longer training regimen. A better understanding of perceptual changes that may follow longer environmental sound training will provide a systematic basis for integrating environmental sounds into training programs for CI patients. As CI candidacy criteria broaden and CI users become more heterogeneous, it is important to learn more about environmental sound awareness and its value to the daily lives of CI users.
Journal Club Highlight
Toward a Nonspeech Test of Auditory Cognition: Semantic Context Effects in Environmental Sound Identification in Adults of Varying Age and Hearing Abilities
PLoS One. 2016;11(11):e0167030. http://bit.ly/2nwpV6C