**3. Auditory processing**

body and (ii) on social and environmental factors that allow the individual to perform his/ her activities and be active socially. Thus, hearing loss should not be a limitation, since it is possible to perform an intervention (hearing aids, implantable hearing aids, and cochlear

When hearing loss is diagnosed, an intervention is necessary. The most immediate solution is the use of a hearing aid (**HA**) technology. The HA is a little apparatus placed in the exter‐ nal meatus and that can amplify the sounds that reach the auditory system. With a hearing aid, the person will regain the audibility even of low‐intensity sounds, making it possible to resume the activities of daily life. The usage of a hearing aid is the primary treatment option

Since elderly subjects present a symmetrical loss profile in most cases, it is possible to use two hearing aid devices and perform a binaural fitting. Two hearing aids favor a better under‐

Currently, in the market, there is a wide variety of technologies for hearing aids and resources that can be used to improve hearing. The best hearing aid is indicated for each case, and for it, a process must be followed by the audiologist, thus favoring a better adaptation of the

This process to determine if a hearing aid should be used or not begins with an assessment and the planning of the intervention to be held. Usually, the individual is subjected to the common audiological tests such as tonal and speech audiometry as well as immittance tympa‐ nometry tests. However, these procedures can only assess hearing complications in the audi‐ tory periphery. The sufficiency of these tests is uncertain and will be further discussed below. The HA is selected based on desired physical and electroacoustic characteristics. At this stage, the individual complains should be considered, their fine motor skills and even cognitive fac‐

Since individuals with sensorineural hearing loss have low speech discrimination in the presence of background noise, most hearing aid devices incorporate noise suppressors that amplify the speech signal over noise and directional microphones that capture best sounds from certain directions. Even in these conditions the hearing aid cannot simulate the cochlea function, for all audible sounds. The hearing aid will amplify certain sound frequencies, but still there will be loss of sound signal quality, and a number of individuals still tend to com‐

The hearing aid should amplify the incoming sounds without being uncomfortable to the per‐ son who uses it. This situation is only possible due to the components and digital or electronic operation of the hearing aid, which will amplify the low‐intensity sounds, transforming them

Care must be taken in the entire process of fitting, such as the handling conditions of the hearing aid by the elderly, the size of the device, or the occurrence of feedback. If any of these

standing of the sound messages and a better localization of the sound source [17].

tors that may influence the use and adaptation of one or other technology.

into audible sounds, without however, causing discomfort in the listener.

implants) and to manage positively the hearing impaired adult [16].

indicated for individuals with nonreversible hearing loss [17].

**2.2. Hearing aids and hearing performance**

plain about the level of amplification.

hearing aid.

114 Advances in Clinical Audiology

In some cases, even if the hearing aid provides audibility of the signal, it cannot improve the listening of the elderly, especially in acoustically unfavorable environments. This may occur because of the listening difficulty caused, including, but not exclusively, by periphery of the auditory system, but also by central portion, in the cortex, thereby generating a difficulty in auditory processing, with consequent difficulty decoding the acoustic signal. This difficulty is not only a result of the increase in hearing thresholds but also of a dysfunction of the auditory processing. This has to be taken into account when selecting hearing aids.

Hearing is a function of the peripheral portion of the auditory system. However, processing and understanding of this sound is a function of the central portion of the auditory system, and incorporates many features and neurological networks, involving aspects like hearing, language, and cognitive.

For a long time, it was believed that only the basic audiological evaluation has been sufficient for diagnosis and intervention in the elderly. Alternatively, the central auditory processing tests should were performed only in individuals with thresholds within normal standard, so that this test is widely used in children with complaints of learning disability without another diagnosis or change detected [19]. However, it is possible to use the auditory processing test with adults and elderly. Several studies [20] on the auditory processing in the elderly or peo‐ ple with hearing loss began to be realized and it looks for the answer of this population, in a way to create a normal answer for this population and investigate if these results can change answer or feeling of the elderly with HA.

It is necessary to consider that it is not only the peripheral portion of the auditory system that is influenced by age, but all the auditory system undergoes aging interference. There may be a drop in auditory skills not only because of a peripheral alteration, but because of a difficulty in working and operating with sounds and auditory skills [21, 22].

Besides the hearing loss, the elderly have trouble in auditory processing. This fact is proven by research showing that older adults with hearing loss perform worse than adults or young people with similar hearing loss. This occurs because there is a deterioration of the central auditory system in the elderly, which generates auditory processing disorder [20]. Especially in the elderly, the acoustic signal that enters the system is distorted due to peripheral hearing loss because of aging (presbycusis) [23], what compromised more the auditory processing. If the whole system is taken into account, only amplification of sound will not be enough, because there can be a change in the processing of this sound in the central portion of the auditory system (cortex). Therefore, this interferes with the fitting of hearing aids, reducing satisfaction and their effective use.

In 1996, the American Speech‐Language‐Hearing Association characterized and defined "*cen‐ tral auditory process are the auditory system mechanisms and process responsible for the following behavioral phenomenal: sound localization and lateralization, auditory discrimination, auditory pat‐ tern recognition, temporal aspects of audition including temporal resolution, temporal masking, tem‐ poral integration and temporal ordering, auditory performance decrements with competing acoustic signals and auditory performance decrements with degraded acoustic signals*" [24].

It is important to evaluate what these abilities mean. When someone can detect from which direction the sound is coming, the person is using the sound localization. When someone can organize or memorize auditory information according to the time, they are developing the temporal ordering ability. When someone understands the auditory information in the competitive noise, they are performing the auditory closure. When someone understands the auditory information from the junction of the information provided in each ear, they are doing binaural synthesis.

In children the auditory processing disorder justifies learning or language disorders. When the sound has not been processed properly, dealing with language issues is difficult, resulting in reading and writing problems. In adults, this change can be detected only when specific or elaborate tasks of listening are requested. In the elderly, the auditory processing difficulty is perceived when the individual does not fit to the hearing aid.

#### **3.1. Auditory processing evaluation**

Therefore, to detect the presence of auditory processing disorders, it is necessary to perform an evaluation, which is conducted in a soundproof booth, using headphones. The assess‐ ment is carried out with different tests, which evaluate the individual auditory skills, such as sound localization, temporal ordering, auditory closure, binaural synthesis, and figure background.

These skills are evaluated using different procedures (**Table 1**), which can be applied in more than one session. Moreover, these tests can be applied in monaural or binaural form, i.e., in order to evaluate just one ear or the binaural integration (both ears). Each test has a specific orientation (purpose) and a specific stimulus. It is not necessary to apply all of the tests. On


**Table 1.** Auditory processing tests and auditory abilities.

a drop in auditory skills not only because of a peripheral alteration, but because of a difficulty

Besides the hearing loss, the elderly have trouble in auditory processing. This fact is proven by research showing that older adults with hearing loss perform worse than adults or young people with similar hearing loss. This occurs because there is a deterioration of the central auditory system in the elderly, which generates auditory processing disorder [20]. Especially in the elderly, the acoustic signal that enters the system is distorted due to peripheral hearing loss because of aging (presbycusis) [23], what compromised more the auditory processing. If the whole system is taken into account, only amplification of sound will not be enough, because there can be a change in the processing of this sound in the central portion of the auditory system (cortex). Therefore, this interferes with the fitting of hearing aids, reducing

In 1996, the American Speech‐Language‐Hearing Association characterized and defined "*cen‐ tral auditory process are the auditory system mechanisms and process responsible for the following behavioral phenomenal: sound localization and lateralization, auditory discrimination, auditory pat‐ tern recognition, temporal aspects of audition including temporal resolution, temporal masking, tem‐ poral integration and temporal ordering, auditory performance decrements with competing acoustic* 

It is important to evaluate what these abilities mean. When someone can detect from which direction the sound is coming, the person is using the sound localization. When someone can organize or memorize auditory information according to the time, they are developing the temporal ordering ability. When someone understands the auditory information in the competitive noise, they are performing the auditory closure. When someone understands the auditory information from the junction of the information provided in each ear, they are

In children the auditory processing disorder justifies learning or language disorders. When the sound has not been processed properly, dealing with language issues is difficult, resulting in reading and writing problems. In adults, this change can be detected only when specific or elaborate tasks of listening are requested. In the elderly, the auditory processing difficulty is

Therefore, to detect the presence of auditory processing disorders, it is necessary to perform an evaluation, which is conducted in a soundproof booth, using headphones. The assess‐ ment is carried out with different tests, which evaluate the individual auditory skills, such as sound localization, temporal ordering, auditory closure, binaural synthesis, and figure

These skills are evaluated using different procedures (**Table 1**), which can be applied in more than one session. Moreover, these tests can be applied in monaural or binaural form, i.e., in order to evaluate just one ear or the binaural integration (both ears). Each test has a specific orientation (purpose) and a specific stimulus. It is not necessary to apply all of the tests. On

*signals and auditory performance decrements with degraded acoustic signals*" [24].

perceived when the individual does not fit to the hearing aid.

in working and operating with sounds and auditory skills [21, 22].

satisfaction and their effective use.

116 Advances in Clinical Audiology

doing binaural synthesis.

background.

**3.1. Auditory processing evaluation**

the other hand, it is necessary to focus on the hearing loss type and its configuration to decide which test is the most important to be performed or can be possibly applied. This analysis is important because the tests are applied with an audible level over the hearing threshold.

Therefore, according to the hearing loss level, one particular test may not be applied because the sound level necessary on that test cannot be reached due to the limitation of the equipment. This aspect will be discussed later on.

#### **3.2. Auditory processing in the elderly**

Research comparing young and old individuals, whose hearing level is within the normal range, observed that even with normal thresholds, there is a reduction in speech understand‐ ing with background noise with the increase of the age of the individuals for short messages (consonants) or for long messages (phrases) [25].

The main complaint of the elderly is the difficulty to understand speech. There are three hypotheses that justify the difficulty to understand speech in the elderly: peripheral hearing loss, central hearing loss, and cognitive impairment. According to studies, despite being the most accepted hypothesis, only peripheral hearing loss may not generate the difficulties to understand the speech in the elderly [26]. In contrast, it adds that changes in auditory process‐ ing could enhance the difficulty that the elderly have to identify speech [27].

It is clear that the elderly has auditory processing disorder, since it is difficult for them to decode phonemes, the perception of rapidly changing speech decoding of verbal and non‐ verbal sounds and a slowing in interhemispheric transmission [28]. These changes associated with the peripheral hearing loss create a difficulty to understand speech, especially if it occurs in an acoustically unfavorable environment.

In addition to the hearing impairment, either peripheral or central, a decline in cognitive func‐ tion can also negatively impact the processing of sound information, impairing speech under‐ standing [29]. With the increase of age there is a decrease in attention span and in working memory, slower brain processing, and reduction in the ability to reduce the environmental interference for speech understanding [6].

Factors such as working memory and speech processing speed influence speech recognition in noise. Studies have shown that the elderly who has a good cognitive performance obtained good results, which were better than those who had poorer performance, indicating that for processing the acoustic signal there is a cognitive interference condition [30].

These cognitive changes associated with the decline in hearing thresholds and a worsening in hearing generates a change in perception and speech understanding in noise. These factors result in a decline in the elderly quality of life and can lead to social isolation [31].

#### **3.3. Auditory processing evaluation in the elderly**

Nowadays, we have the idea that there is a correlation between auditory processing tests and hearing loss and that the elderly performs worse than adults. Because of that, recent research includes study of the auditory processing and hearing loss, and look for a way to evaluate and intervene with this population.

In the elderly, it is essential to consider the presence of peripheral hearing loss, but as it is a poor signal that reaches the cerebral cortex due to peripheral hearing loss, cognition of the elderly is fundamental for a better understanding of the message. Additionally, the auditory cortex of individuals in this portion of the population tends to atrophy, which causes a change in auditory processing, i.e., the sound that enters the system is already an altered sound, and it worsens because of the way this is processed [31].

Studies show that seniors who have changes in auditory processing tend to perform a self‐ assessment of the hearing handicap worse than those who have no auditory processing disor‐ der, showing that it is necessary for a better evaluation of each individual [32].

Some researches specify types of responses that can be obtained for each case. Individuals with low‐ and high‐frequency hearing loss show difficulty in monotonic tasks. In turn, the elderly with hearing loss in high frequency or normal hearing can perform well on these tests. Therefore, audiological characteristics of the hearing loss have to be taken into account to select the processing test and understand the results achieved [33].

Many factors have to be considered to assess auditory processing in the elderly. In addition to care in the test selection, it is important to consider the age of the assessed person. It is known that when comparing the performance of adults with the elderly performance, the elderly will have a lower performance than adults, those observed even in the presence of similar hearing loss. This occurs because there is a deterioration of the central auditory system, which gener‐ ates an auditory processing disorder in the elderly. This context interferes negatively with the hearing aids' fitting, reducing the satisfaction of the elderly in relation to these devices, resulting in a noneffective use [22].

To evaluate how the elderly process this sound, or their listening skills, it can map out a more detailed and correct rehabilitation plan for each case. If there is the presence of periph‐ eral hearing loss, hearing aids must be fitted. However, with a broader look at the elderly's auditory system and their greatest difficulties, a better hearing aid fitting is possible, as well as the indication of a therapy or auditory training.

However, still in the assessment phase, it is important that the evaluator considers the pres‐ ence of peripheral hearing loss when selecting and evaluating the results of tests of auditory processing, since not all tests can be applied in cases of peripheral hearing loss. It is neces‐ sary to select tests that do not suffer interference from hearing loss. Still, there is the degree of limitation of loss, with the possible application in symmetrical hearing loss, from mild to moderate (hearing loss up to 55 dB HL) [34].

Some authors suggest that the battery used to assess auditory processing should have dichotic tests, temporal processing tests, low redundancy monaural tests, and binaural interaction tests [34, 35].

Specifically to evaluate the binaural interaction, it is suggested to use the dichotic digits test. Studies show that there is a drop in performance of the left ear in the dichotic listening in the elderly. This generates a change in interhemispheric transfer of the acoustic signal, which is due to the deterioration of the callosum corpus [36]. This change in dichotic listening can alter also in working memory and selective attention, suggesting cognitive impairment [37, 38].

It is important to explain that in the dichotic test, four numbers are introduced. First of all, two numbers will be shown, at same time, but each one in each ear. Immediately after, other two numbers are shown in the same way. The listener has to pay attention and tell which numbers he listened and/or what numbers were heard in each ear.

In this age group (elderly), more problems are observed with listening skills figure back‐ ground and closing, which affect the listening speech in noise in acoustically unfavorable environments. In addition, changes in auditory temporal processing are also observed in the elderly and widely discussed in the literature [39]. It is believed that the elderly people experi‐ ence changes in auditory temporal processing, which can be detected both in frequency and in test duration [6].

In the temporal tests, three stimuli in sequence are presented, and the assessed individual has to name or reproduce the sound, and thick or thin the frequency test, or long and short in duration test.

The hearing performance worsens with the presentation of a complex or an acoustically unfa‐ vorable environment stimulus. Added to this, the elderly has great difficulty with sequencing activities, which involve auditory processing and cognition [40].
