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Hearing loss is often overlooked because our hearing is an invisible sense that is always expected to be in action. Yet, there are people everywhere that suffer from the effects of hearing loss. It is important to study and understand all aspects of the many different types and reasons for hearing loss. The loss of this particular sense can be socially debilitating. It can affect the communication skills of the person, not only in receiving information, but also in giving the correct response. This paper focuses primarily on hearing loss in the elderly. One thing that affects older individuals' communication is the difficulty they often experience when recognizing time compressed speech. Time compressed speech involves fast and unclear conversational speech. Many older listeners can detect the sound of the speech being spoken, but it is still unclear (Pichora-Fuller, 2000). In order to help with diagnosis and rehabilitation, we need to understand why speech is unclear even when it is audible. The answer to that question would also help in the development of hearing aids and other communication devices. Also, as we come to understand the reasoning behind this question and as we become more knowledgeable about what older adults can and cannot hear, we can better accommodate them in our day to day interactions.

There are many approaches to the explanation of the elderly's difficulty with rapid speech. Researchers point to a decline in processing speed, a decline in processing brief acoustic cues (Gordon-Salant & Fitzgibbons, 2001), an age-related decline of temporal processing in general (Gordon-Salant & Fitzgibbons, 1999; Vaughan & Letowski, 1997), the fact that both visual and auditory perception change with age (Helfer, 1998), an interference of mechanical function of the ear, possible sensorineural hearing loss due to damage to receptors over time (Scheuerle, 2000), or a decline in the processing of sounds in midbrain (Ochert, 2000). Each one of these could be a possible explanation; however it is often a combination of several of these causing a perceptual difficulty in the individual.

Helfer (1998) recognized the slowing of our temporal perceptual processes with increasing age. He suggested that this leads to auditory deformity, especially in the instance of time compressed speech. Speech comprehension requires rapid processing of stimuli that is not always completed in time-compressed speech because of the shortening of phonemes and a decrease in pauses. Helfer went a step further by taking into account that hearing is not just auditory but it is also visual, in that we use cues like looking at the person's mouth or facial expression while having a conversation. As he studied how much older adults rely on visual cues, he began to realize that in order to help the elderly comprehend we must not only slow down our speech rate, but we must also give them a lot of visual cues. Again, this researcher pointed to the impact that cognitive aging has on the perceptual processing.

Gordon- Salant & Fitzgibbons (2001) approached the question of whether the age-related decline in understanding rapid speech is attributed to a decline in processing speed or a decline in processing brief acoustic cues. By testing both young and old participants, they found that older adults were affected when linguistic information was missing because there were time-compressed vowels, consonants, or pauses. It is quite possible that the cognitive demand to recognize speech of that nature has been affected by the aging process. Another interesting find in this study was that in time-compressed speech, there is more of a lack of consonants than of vowels and pauses. This means that when talking to older adults the rate of speech should be slow and there should be deliberate articulation of consonants. The latter finding answers the earlier question; it is not that the older adult loses speech recognition because of a slowing in their processing speed. Instead, it is the loss of the consonant acoustic cues that affects recognition of rapid speech. Through this study, the authors found that the perception of time-compressed speech is also influenced when there is a loss of contextual cues, such as the facial expressions mentioned above.

Another more in-depth exploration of the temporal processing explanation involves an age-related decline in central timing and a subsequent increase in perceptual information overload. An individual's temporal processing influences peripheral, central, and cognitive processing capacities. Gordon-Salant & Fitzgibbons (1999) looked at the possibility that an older adult's temporal resolving power might become encumbered during rapid speech with transient consonant cues. It was found that to discriminate the missing information that gets lost in rapid speech, older adults need almost three times longer than younger listeners (95.6 ms vs. 35.0 ms). They suggested that there is a decay of central timing mechanisms that affects the older adult's recognition capacities. Vaughan & Letowski (1997) examined not only the effects of the rate of speech but also the demand that the length of the material being presented puts on the temporal processing of the elderly. With age, the temporal processing capacity of the auditory system can become overloaded in the event that there is ongoing, rapid speech. Because these researchers studied young, middle-aged, and older participants, they found that this somewhat debilitating change of our auditory processing system begins in the middle-aged years of forty-five to fifty-five. Both of these studies found that a 70% compression rate was enough of an increase in the rate of speech to show a significant difference in age and understanding. For example if there was a 172 wpm average, a 70% time compression of that average would be 540 wpm. From this evidence, it is apparent that our ability to efficiently process time-compressed speech has a cognitive explanation.

It is important now to turn attention toward some common physical aspects that often affect the older listener. The system of parts necessary for hearing is composed of three chambers, which act as the channels through which sound waves are received to activate the eighth cranial nerve, which in turn activate the temporal lobe of the brain. Jane Scheuerle (2000) points to two types of obstacles that can hinder of this process. The first type of interference can weaken the strength of the sound wave energy that reaches the inner ear by preventing sound waves from reaching the auditory receptors. This could occur because of impacted cerumen, or ear wax, in the outer ear or because of middle ear problems, such as otitis media. The perception of conversational speech is then hindered because the brain does not have access to phonemes like r, l, n, sh, p, f, and th. Phonemes are the smallest unit of speech that is capable of conveying a distinction of meaning. The second type of obstacle affects the perception of high frequencies and involves the failing of neurological components. This dysfunction is called sensorineural hearing loss and it can occur after years of noise, trauma, and illness. Individuals suffering from this cannot hear phonemes like p, h, sh, ch, f, s, and th. With both of these types of disorders, most of the speaker's message is not registering with the listener. This makes it very hard for the listener to make sense of anyone talking to him/her, thus leading to negative social implications. The stimulus of hearing is fleeting. A person with any type of interference often scrambles for an appropriate response to even the simplest of questions.

One more cognitive explanation involves current research that has begun to surface about the midbrain and its effect on hearing loss (Ochert, 2000). With aging comes the difficulty of identifying the gaps between vowels and the high-pitched hisses of consonants. It has been found that aging mice lose about half of their nerve cells that detect those gaps. Other research has found that the human auditory midbrain, and area that helps process sounds, is not as active in older adults. It has also recently been found that younger adults have a higher level of calcium going into and coming out of the actual cells in this region. These are recent and exciting discoveries that will be studied further. Until they are, we need to keep in mind that elderly people have these hindrances, and we must be sensitive by talking more clearly and slowly. Hence, there are other physiological influences on hearing loss besides that of the decrease in temporal processing that was mentioned above.

Current and ongoing research will continue to focus on aging in relation to auditory function and auditory temporal processing deficits. Risk factors that contribute to age-related hearing loss are also being studied. Current studies are investigating further the slowing of temporal processing over time. To measure this they increase stimulus and task complexity, and then identify specific stimulus characteristics that contribute to the elderly person's perceptual difficulties (Gordon-Salant & Fitzgibbons, 2001). It is important to continue these studies to further the clinical applications of helping individuals receive training for temporal cues and in general, to make their communication easier. There is future research that will examine the effects of intensity and rate of speech on intelligibility (Vaughan and Letowski, 1997). Speech intelligibility tests are important because they help with hearing aid fittings. The ultimate plan is for digital hearing aids to transform conversational speech into clear speech one day (Helfer, 1998). The work in this field is ongoing and very important to the happiness of many struggling elderly people.

References

Gordon-Salant, S,. & Fitzgibbons, P. J. (1999). Profile of auditiory processing in older listeners. Journal of Speech, Language, and Hearing Research, 42, 300-310.

Gordon-Salant, S., & Fitzgibbons, P.J. (2001). Sources of age-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 of clear and conversational speech by older adults. Journal of the American Academy of Audiology, 9.

Ochert, A. (2000). Brain, not just ears, loses hearing. Science Now, 1.

Pichora-Fuller, M.K. (2000). Time and timing: Age-related differences in auditory, speech, language, and cognitive processing. Acoustical Society of America 139th Meeting Lay Language Papers.

Scheuerle, J. (2000). Hearing and aging. Educational Gerontology, 26, 237-247.

Vaughan, N.E., & Letowski T. (1997). Effects of age, speech rate, and type of test on temporal auditory processing. Journal of Speech, Language, and Hearing Research, 40, 1192-1200.