Ryota Shimokura Ryota Shimokura

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http://dx.doi.org/10.5772/intechopen.73527

*"Blindness cuts you off from things; deafness cuts you off from people."*

*Immanuel Kant (Philosopher, 1724–1804).*

#### **Abstract**

This chapter presents an overview of the current state of a hearing aid tracing back through the history. The hearing aid, which was just a sound collector in the sixteenth century, has continued to develop until the current digital hearing aid for realizing the downsizing and digital signal processing, and this is the age of implanted hearing devices. However, currently popular implanted hearing devices are a fairly large burden for people soon after they become aware of their hearing loss, although auditory stimulation to the nerve in the early stage can avoid accelerated cognitive decline and an increased risk of incident all-cause dementia. For this reason, we tend to stick to wearable hearing aids that are easy to be put on and take off. Although the digital hearing aid has already reached the technical ceiling, the noninvasive hearing aids have some severe problems that are yet to be resolved. In the second half of this chapter, we discuss the scientific and technical solutions to broaden the range of permissible users of hearing aids.

DOI: 10.5772/intechopen.73527

**Keywords:** dementia, EuroTrak, bone-conducted ultrasonic hearing aid, cartilage conduction hearing aid, autocorrelation analysis

#### **1. Introduction**

When the ability to hear declines, people become uncomfortable during conversations and gradually begin to speak less and less. This worsening situation can lead to depression and an increased risk of dementia. In 2015, the Ministry of Health, Labour and Welfare in Japan published an initiative for preventing dementia (New Orange Plan), which states that hearing loss is a risk for declining cognitive function [1]. The first report to show the relationship between

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

hearing impairment and dementia was published in 1989 [2], and several longitudinal studies that included auditory and nonauditory cognitive testing have shown that people with hearing loss have a 30–40% rate of accelerated cognitive decline [3] and an increased risk of incident allcause dementia [4, 5]. The implications are that auditory stimulation that reaches the brain can delay aging of the brain and allow communication with family and society to continue. Thus, the earlier that people can receive audiological treatment and hearing aid prescriptions, the better.
