Stephen F. Austin State University
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Hearing loss is often overlooked because our hearing is aninvisible sense that is always expected to be in action. Yet, thereare people everywhere that suffer from the effects of hearing loss.It is important to study and understand all aspects of the manydifferent types and reasons for hearing loss. The loss of thisparticular sense can be socially debilitating. It can affect thecommunication skills of the person, not only in receivinginformation, but also in giving the correct response. This paperfocuses primarily on hearing loss in the elderly. One thing thataffects older individuals' communication is the difficulty they oftenexperience when recognizing time compressed speech. Time compressedspeech involves fast and unclear conversational speech. Many olderlisteners can detect the sound of the speech being spoken, but it isstill unclear (Pichora-Fuller, 2000). In order to help with diagnosisand rehabilitation, we need to understand why speech is unclear evenwhen it is audible. The answer to that question would also help inthe development of hearing aids and other communication devices.Also, as we come to understand the reasoning behind this question andas we become more knowledgeable about what older adults can andcannot hear, we can better accommodate them in our day to dayinteractions.
There are many approaches to the explanation of the elderly'sdifficulty with rapid speech. Researchers point to a decline inprocessing speed, a decline in processing brief acoustic cues(Gordon-Salant & Fitzgibbons, 2001), an age-related decline oftemporal processing in general (Gordon-Salant & Fitzgibbons,1999; Vaughan & Letowski, 1997), the fact that both visual andauditory perception change with age (Helfer, 1998), an interferenceof mechanical function of the ear, possible sensorineural hearingloss due to damage to receptors over time (Scheuerle, 2000), or adecline in the processing of sounds in midbrain (Ochert, 2000). Eachone of these could be a possible explanation; however it is often acombination of several of these causing a perceptual difficulty inthe individual.
Helfer (1998) recognized the slowing of our temporal perceptualprocesses with increasing age. He suggested that this leads toauditory deformity, especially in the instance of time compressedspeech. Speech comprehension requires rapid processing of stimulithat is not always completed in time-compressed speech because of theshortening of phonemes and a decrease in pauses. Helfer went a stepfurther by taking into account that hearing is not just auditory butit is also visual, in that we use cues like looking at the person'smouth or facial expression while having a conversation. As he studiedhow much older adults rely on visual cues, he began to realize thatin order to help the elderly comprehend we must not only slow downour speech rate, but we must also give them a lot of visual cues.Again, this researcher pointed to the impact that cognitive aging hason the perceptual processing.
Gordon- Salant & Fitzgibbons (2001) approached the question ofwhether the age-related decline in understanding rapid speech isattributed to a decline in processing speed or a decline inprocessing brief acoustic cues. By testing both young and oldparticipants, they found that older adults were affected whenlinguistic information was missing because there were time-compressedvowels, consonants, or pauses. It is quite possible that thecognitive demand to recognize speech of that nature has been affectedby the aging process. Another interesting find in this study was thatin time-compressed speech, there is more of a lack of consonants thanof vowels and pauses. This means that when talking to older adultsthe rate of speech should be slow and there should be deliberatearticulation of consonants. The latter finding answers the earlierquestion; it is not that the older adult loses speech recognitionbecause of a slowing in their processing speed. Instead, it is theloss of the consonant acoustic cues that affects recognition of rapidspeech. Through this study, the authors found that the perception oftime-compressed speech is also influenced when there is a loss ofcontextual cues, such as the facial expressions mentioned above.
Another more in-depth exploration of the temporal processingexplanation involves an age-related decline in central timing and asubsequent increase in perceptual information overload. Anindividual's temporal processing influences peripheral, central, andcognitive processing capacities. Gordon-Salant & Fitzgibbons(1999) looked at the possibility that an older adult's temporalresolving power might become encumbered during rapid speech withtransient consonant cues. It was found that to discriminate themissing information that gets lost in rapid speech, older adults needalmost three times longer than younger listeners (95.6 ms vs. 35.0ms). They suggested that there is a decay of central timingmechanisms that affects the older adult's recognition capacities.Vaughan & Letowski (1997) examined not only the effects of therate of speech but also the demand that the length of the materialbeing presented puts on the temporal processing of the elderly. Withage, the temporal processing capacity of the auditory system canbecome overloaded in the event that there is ongoing, rapid speech.Because these researchers studied young, middle-aged, and olderparticipants, they found that this somewhat debilitating change ofour auditory processing system begins in the middle-aged years offorty-five to fifty-five. Both of these studies found that a 70%compression rate was enough of an increase in the rate of speech toshow a significant difference in age and understanding. For exampleif there was a 172 wpm average, a 70% time compression of thataverage would be 540 wpm. From this evidence, it is apparent that ourability to efficiently process time-compressed speech has a cognitiveexplanation.
It is important now to turn attention toward some common physicalaspects that often affect the older listener. The system of partsnecessary for hearing is composed of three chambers, which act as thechannels through which sound waves are received to activate theeighth cranial nerve, which in turn activate the temporal lobe of thebrain. Jane Scheuerle (2000) points to two types of obstacles thatcan hinder of this process. The first type of interference can weakenthe strength of the sound wave energy that reaches the inner ear bypreventing sound waves from reaching the auditory receptors. Thiscould occur because of impacted cerumen, or ear wax, in the outer earor because of middle ear problems, such as otitis media. Theperception of conversational speech is then hindered because thebrain does not have access to phonemes like r, l, n, sh, p, f, andth. Phonemes are the smallest unit of speech that is capable ofconveying a distinction of meaning. The second type of obstacleaffects the perception of high frequencies and involves the failingof neurological components. This dysfunction is called sensorineuralhearing loss and it can occur after years of noise, trauma, andillness. Individuals suffering from this cannot hear phonemes like p,h, sh, ch, f, s, and th. With both of these types of disorders, mostof the speaker's message is not registering with the listener. Thismakes it very hard for the listener to make sense of anyone talkingto him/her, thus leading to negative social implications. Thestimulus of hearing is fleeting. A person with any type ofinterference often scrambles for an appropriate response to even thesimplest of questions.
One more cognitive explanation involves current research that hasbegun to surface about the midbrain and its effect on hearing loss(Ochert, 2000). With aging comes the difficulty of identifying thegaps between vowels and the high-pitched hisses of consonants. It hasbeen found that aging mice lose about half of their nerve cells thatdetect those gaps. Other research has found that the human auditorymidbrain, and area that helps process sounds, is not as active inolder adults. It has also recently been found that younger adultshave a higher level of calcium going into and coming out of theactual cells in this region. These are recent and excitingdiscoveries that will be studied further. Until they are, we need tokeep in mind that elderly people have these hindrances, and we mustbe sensitive by talking more clearly and slowly. Hence, there areother physiological influences on hearing loss besides that of thedecrease in temporal processing that was mentioned above.
Current and ongoing research will continue to focus on aging inrelation to auditory function and auditory temporal processingdeficits. Risk factors that contribute to age-related hearing lossare also being studied. Current studies are investigating further theslowing of temporal processing over time. To measure this theyincrease stimulus and task complexity, and then identify specificstimulus characteristics that contribute to the elderly person'sperceptual difficulties (Gordon-Salant & Fitzgibbons, 2001). Itis important to continue these studies to further the clinicalapplications of helping individuals receive training for temporalcues and in general, to make their communication easier. There isfuture research that will examine the effects of intensity and rateof speech on intelligibility (Vaughan and Letowski, 1997). Speechintelligibility tests are important because they help with hearingaid fittings. The ultimate plan is for digital hearing aids totransform conversational speech into clear speech one day (Helfer,1998). The work in this field is ongoing and very important to thehappiness of many struggling elderly people.
Gordon-Salant, S,. & Fitzgibbons, P. J. (1999). Profile ofauditiory processing in older listeners. Journal of Speech,Language, and Hearing Research, 42, 300-310.
Gordon-Salant, S., & Fitzgibbons, P.J. (2001). Sources ofage-related recognition difficulty for time-compressed speech.Journal of Speech, Language, and Hearing Research, 44,709.
Helfer, K.S., (1998). Auditory and auditory-visual recognition ofclear and conversational speech by older adults. Journal of theAmerican Academy of Audiology, 9.
Ochert, A. (2000). Brain, not just ears, loses hearing. ScienceNow, 1.
Pichora-Fuller, M.K. (2000). Time and timing: Age-relateddifferences in auditory, speech, language, and cognitive processing.Acoustical Society of America 139th Meeting Lay LanguagePapers.
Scheuerle, J. (2000). Hearing and aging. EducationalGerontology, 26, 237-247.
Vaughan, N.E., & Letowski T. (1997). Effects of age, speechrate, and type of test on temporal auditory processing. Journal ofSpeech, Language, and Hearing Research, 40, 1192-1200.