**2. Hearing**

The concept of hearing is extremely complex and goes beyond the simple act of listening to a particular sound. This is a process in which motor, electrical, and biochemical changes occur along the auditory path inside the human body, which begins in the outer ear (more specifically in the pinna), and ends in the cortex, where the sound information received is decoded [3].

Sound waves generated in the environment are captured by the pinna and driven by the external acoustic meatus to the tympanic membrane, which starts a vibration process, trans‐ forming the sound waves into mechanical waves. This vibration moves the ossicles in the middle ear until it reaches the oval window, where stimulation will reach the inner ear.

The movement that begins in the inner ear promotes movement in the liquid (endolymph) that is housed in the cochlea, as well as, a change in its structures, promoting the excitement of the outer and inner hair cells, which in turn stimulate a network of nerve endings, which leads to the stimulation of the cochlear nerve to reach the central nervous system. It will be in the cerebral cortex that the stimulus will be decoded and then spatially interpreted.

As described above, hearing is an extremely complex process. What happens when the audi‐ tory system is affected by changes due to aging and it does not work properly?

### **2.1. Hearing loss and its consequences**

When the auditory system presents structural changes, other disorders might be observed first, depending on the location where the hearing complications were first observed. For example, if a problem is observed in the external, middle, or inner ear, it will result in a reversible (or not) hearing loss. If a problem is present in the area of the auditory cortex, it will generate a processing interference, which will affect the understanding and decoding of the incoming sound stimuli.

Associated with the transformation of the body and with the higher incidence of health com‐ plications, the elderly may present sensory, motor, and cognitive alterations. Cellular and molecular damage may also show up due to aging, possibly resulting in sensory loss (hearing or vision) or motor disability. In addition, cognitive changes such as decreased attention and

All these factors may compromise the quality of life and the independence of the elderly. In addition, these changes can lead this segment of the population to a social isolation and

The aging of the auditory system leads to physical, sensory, and neural changes in the peripheral and central portion of the system, which may also cause changes in the sections

The objective of this chapter is to make a review of hearing loss and auditory processing, while considering the use of amplification technologies (hearing aids) and their intervention

The concept of hearing is extremely complex and goes beyond the simple act of listening to a particular sound. This is a process in which motor, electrical, and biochemical changes occur along the auditory path inside the human body, which begins in the outer ear (more specifically in the pinna), and ends in the cortex, where the sound information received is

Sound waves generated in the environment are captured by the pinna and driven by the external acoustic meatus to the tympanic membrane, which starts a vibration process, trans‐ forming the sound waves into mechanical waves. This vibration moves the ossicles in the middle ear until it reaches the oval window, where stimulation will reach the inner ear.

The movement that begins in the inner ear promotes movement in the liquid (endolymph) that is housed in the cochlea, as well as, a change in its structures, promoting the excitement of the outer and inner hair cells, which in turn stimulate a network of nerve endings, which leads to the stimulation of the cochlear nerve to reach the central nervous system. It will be in

As described above, hearing is an extremely complex process. What happens when the audi‐

When the auditory system presents structural changes, other disorders might be observed first, depending on the location where the hearing complications were first observed. For example, if a problem is observed in the external, middle, or inner ear, it will result in a reversible (or not) hearing loss. If a problem is present in the area of the auditory cortex, it

the cerebral cortex that the stimulus will be decoded and then spatially interpreted.

tory system is affected by changes due to aging and it does not work properly?

working memory may also be present [1, 2].

which receive and process the sound stimuli.

**2.1. Hearing loss and its consequences**

depression [1].

112 Advances in Clinical Audiology

in the elderly.

**2. Hearing**

decoded [3].

Aging processes can alter the structures of the auditory system, resulting in hearing loss and a compromise of hearing. This is the most significant and important sensory change in the lives of the elderly, which can generate a social limitation, minimizing the social function and the participation of the elderly in the society [4].

Hearing loss due to aging is called "*presbycusis*" or *age‐related hearing loss* (ARHL) [5]. It is usu‐ ally identified due to complains from the elderly subjects, referring to difficulties in under‐ standing nearby sounds, especially in environments with poor acoustics. In these cases, an audiological assessment usually results in an identification of a mild‐to‐moderate symmetric sensorineural hearing loss, which worsens in the course of time [6].

It is well known that 80% of the population >85 years present some form of hearing loss [7]. The incidence of the hearing impairment also has gender effects, i.e., elderly men tend to be more affected than elderly women [8].

The data in the literature show that presbycusis can be classified into three types: the **sensory** presbycusis, the **neuronal** presbycusis, and the **metabolic** presbycusis [9, 10]. In the first case, it is possible to observe a lesion in the organ of Corti, which results in an audiogram with sloping configuration. In the **neuronal** presbycusis, there is a loss of spiral ganglion neurons, which leads to a worsening in speech discrimination, which does not seem compatible with hearing loss observed in the audiogram. The **metabolic** presbycusis is caused by a degenera‐ tion of the vascular stria, characterized by a vocal discrimination preserved, even in spite of the presence of flat or high frequency configuration [9, 10]. In all the three cases above, the elderly is considered to have a sensory neural hearing loss.

However, it is necessary to account for other factors that may have affected the hearing of the elderly throughout life and that may have worsened the hearing loss, such as exposure to noise, cardiovascular diseases (hypertension or diabetes), or extensive use of antineoplastic drugs. Very often what we call presbycusis is the cumulative effect of aging with cochlear stress caused by other etiologies [11–13].

A decline of the linguistic functions is commonly observed in the elderly presenting hearing loss. Due to this sensorial disorder, an elderly subject loses the quality of sound information in communicating with others, which may generate at first a difficulty or trouble understanding a vocal message, and eventually drives the elderly into social isolation [14]. This situation has an impact in the lives of the elderly as well as in the people who surround the elderly, their caregivers.

These communication difficulties are global and they are changing the life of the elderly, reducing their communication skills with members of the family or friends. This difficulty can even show up with normal environmental sounds such as a telephone ring or the horn of a car, situations that can even put the elderly into a safety hazard [15].

The International Classification of Disability and Health (ICF) (World Health Organization, 2001) considers that a condition of good health depends (i) on the proper functioning of the 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 implants) and to manage positively the hearing impaired adult [16].

#### **2.2. Hearing aids and hearing performance**

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 indicated for individuals with nonreversible hearing loss [17].

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

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 hearing aid.

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

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‐ plain about the level of amplification.

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

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 factors were not observed, the chance of the elderly not making effective use of the hearing aid is very high.

After selecting the best hearing aid for the subject case and its characteristics, the specific device performance and the individual performance with this technology must be verified through objective and subjective tests if there was an improvement in the perception of sound stimuli. The next phase consists of providing the user with proper guidance on the usage and handling of the hearing aid, enabling, after one‐time use, the validation of the treatment, in other words, the perception of the impact of the intervention in the life of the new user of hearing aids [18]. Throughout this process, the audiologist should consider two important factors: the limitations in activities and participation restriction.

For this reason, even with the existing technological advancements in the field of hearing aids, some elderly subjects still complain about the amplification, signal quality, often failing to make use of this technology. Other elderly subjects, in turn, report great improvement in their lives with the use of hearing aids, accomplishing different listening tasks. So, why does it occur?
