Hearing aids have evolved from simple amplifiers to include features that not only allow people with hearing impairments to hear in difficult situation, 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/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, the 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 contained and 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 had been developed that allow the user to direct a “beam” from the directional microphone to target 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 improved communication in typical noisy environments such as restaurants, etc. Another unique feature is an algorithm that can detect and reduce the effect of wind noise. This is especially useful for individuals that enjoy outdoor activities such as golf, bicycle riding, etc. 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, fans, etc., which 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 conversations with others and one 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 several shaped noises. In addition, several therapy sounds have modulated signals that mimic ocean waves. One unique therapy sound has fractal signals. 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 mobile phone that contains key information on the operation of the hearing aid. The hearing professional can send updated programs directly to their phone, or connect via the chat function on the users’ mobile phone for a quick chat if information is required for a specific listening environment. One recent introduced application 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 hearing aid industry employs over 6,000 people in the R&D area and spends between 8-10% of their annual budgets on R&D activities. The timeline for a new product starts approximately 3 years prior to the launch when the initial brainstorming on the new features take 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, housings, 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.