Developing an Appropriate Digital Hearing Aid for Low-Resource Countries

This paper reviews the development process and discusses the key findings which resulted from our multidisciplinary research team’s effort to develop an alternative digital hearing suitable for low-resource countries such as Thailand. A cost-effective, fully programmable digital hearing aid, with its specifications benchmarking against WHO’s recommendations, was systematically designed, engineered, and tested. Clinically it had undergone a full clinical trial that employed the outcome measurement protocol adopted from the APHAB, the first time implemented in the Thai language. Results indicated that using the hearing aid improves user’s satisfaction in terms of ease of communication, background noises, and reverberation, with clear benefit after 3 and 6 months, confirming its efficacy. In terms of engineering, the hearing aid also proved to be robust, passing all the designated tests. As technology has successfully been transferred to a local company for the production phase, we also discuss other challenges that may arise before the device can be introduced into the market.

Introduction

The World Health Organization (WHO) has estimated in 2005 that 278 million of the world population may have hearing difficulties. In Thailand, data from the last survey by the National Statistical Office in 2007 indicates that there were 384,992 hearing impaired persons in Thailand. Moreover, according to a national health survey during 2008-2009, 28% of the elderly were found to have hearing difficulties. The situation will get worse as the country’s demography is shifting towards an aging society. For those with hearing impairment who can benefit from wearing hearing aids, the use of such devices has not been widespread. Even in the USA, less than 25% of those who could benefit from using hearing aids actually own them. The situation is worse in developing countries such as Thailand. Historically, this was partly due to the analog technology that failed to provide the owners with satisfying results. Increasingly, however, modern hearing aids employ digital technology that shows significant improvements in terms of performance. Many advanced features that were not available in analog technology are now being realized using digital signal processing (DSP) technology. Unfortunately, these devices come with higher prices and become unaffordable for users to benefit, especially in developing countries.

In principle, Rechargeable hearing aids supplier are devices that amplify and customize incoming sound signals to meet specific requirements of each hearing impaired. For a digital hearing aid, the sound is picked up via its microphone(s) and converted into the digital form that is processed according to predefined DSP algorithms tailored for each patient’s requirements. The modified signal is converted back to the analog form for the receiver to convert it into sound waves and send them directly into the ear. Through this process, precise amplification characteristics desired can be achieved. Today, there are various types of hearing aids (both analog and digital) on the market, from body-aid (or pocket-type) to BTE (behind-the-ear), ITE (in-the-ear), ITC (in-the-canal), or CIC (completely-in-the-canal). These readily available devices offer choices on both price and performance. It is believed, however, that there are still demands for alternative hearing aid devices that are not readily available on the market. This can particularly be true in developing countries, where desirable features such as cost-effectiveness, ease of use and maintenance, and fully digital processing capability are imperative.

This paper discusses the development of an indigenous digital hearing aid targeted for rural usage. The result is a fully digital hearing aid that is designed for those with moderate-to-severe hearing loss. It comes in the shape of a pocket-type to meet the specific requirements for ease of use and robustness against extreme conditions of rural usage. The form factor also allows us to have an appropriate battery system that helps address the issue of maintenance cost. The hearing aid was systematically designed, engineered, and tested acoustically, functionally, and clinically. The design has now successfully been licensed out for local production.

The paper is organized as follows: Section discusses development methods. This includes design and engineering issues and acoustical, clinical, and functional test setups. Section reports the results. Further discussions are given in Section, including issues to be considered before the device can be market-ready. Section concludes the work.