by Thomas A. Powers, PhD
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This content originally appeared on BetterHearing.org, the website of the US-based Hearing Industries Association. It has been republished with their permission.
Hearing aids have evolved from simple amplifiers to include features that not only allow people with hearing impairments to hear in difficult situations, but to assist with health-related activities. The introduction of digital circuits over 20 years ago greatly improved the processing power of hearing aids. The current devices contain more processing power than the circuits and computers that helped put a man on the moon!
To take a tour of a modern hearing aid, we should review the four key components: the microphone, receiver, amplifier/circuit, and the power supply. The microphone and receiver (a term borrowed from telephone technology) are also referred to as transducers. The microphone picks up signals and sends them to the amplifier where the digital signal processing power of today’s hearing aid is applied. The signals are sent from the amplifier to the loudspeaker and on to the user’s ear. The power supply can be either a replaceable battery or one that is rechargeable.
One of the most difficult environments for people with hearing impairments is when background noise is present. To assist in reducing the effect on conversation, new directional microphone techniques have been developed that allow the user to direct a “beam” from the directional microphone toward the speaker or signal the user is interested in. These “beams” can be directed to the front, side, or to the rear, and have been shown to improve communication in typical noisy environments such as restaurants. Another unique feature is an algorithm that can detect and reduce the effect of wind noise. This is especially useful for individuals who enjoy outdoor activities such as golfing or bicycle riding. The two-microphone design of directional microphones can detect the turbulence that is created by the wind hitting the two microphones. Since this signal is different than speech or car noise, it can be classified and reduced using sophisticated signal processing. Another common algorithm can identify and reduce the level of stationary background noises (such as cars, vacuums, and fans) and provides a reduction of listening effort in these environments.
Another concern of the hearing aid wearer is the sound of their own voice. A new algorithm conducts a training session on the user’s voice and then adapts the amplification into two pathways, one for listening to conversation and one for when the user is speaking. This reduces the perception of one’s own voice to be different or unnatural and increases the satisfaction of the device.
For individuals with tinnitus, new sound therapies have emerged. These include traditional sound maskers which can be white noise or masking noises shaped with more bass or treble emphasis. In addition, several therapy sounds have modulated signals that mimic ocean waves. One unique therapy sound utilizes tones, harmonies, or musical chimes to alleviate tinnitus. Due to the individual nature of the tinnitus sound experience, these sound therapies should be discussed with your hearing professional.
Hearing aids have been expanding the use of telehealth applications to include remote programming and monitoring of bio-metric data. The local hearing care professional can provide the user with access to an app for their smartphone that contains key information on the operation of the hearing aid. Through the app, the hearing professional can also send updated programs or connect via the chat function for a quick call if information or assistance is required for a specific listening environment. A newer innovation can detect if the user has fallen and can send a text message to an emergency contact stored in the phone.
To achieve these ground-breaking applications, it takes a small city of engineers, software developers and many other Research and Development (R&D) staff. The timeline for a new product starts approximately three years prior to the launch when the initial brainstorming on the new features takes place. Once the feature set is outlined, the real development activities begin. It usually takes between 18-24 months to develop the signal processing algorithms, software, housing, and related accessories.
As the development of the signal processing progresses, the regulatory processes also must be completed. These include submissions to a variety of federal organizations in over 100 countries. In addition, safety and quality milestones are completed to ensure the devices meet, or exceed, the latest regulations.
Future applications may include additional sensors for various health related monitoring. Hearing instruments will continue to add communication and health related applications to provide enhanced benefits and increase satisfaction for the millions of hearing aid users.
