R&D Blog

The R&D Blog is a forum for manufacturers to share their latest research and news, but more importantly is a place for readers to comment and discuss new developments with them. Above all, it is a forum for opinions, questions, and discussions about hearing aid technology between manufacturers and hearing healthcare professionals. Submit an article for the R&D Blog by sending it to the editor at HJ@wolterskluwer.com. Articles should be no more than 1,500 words, and will be reviewed and edited before posting. Readers may submit comments, which will be moderated, by clicking the link below.

Friday, August 31, 2012

Binaural Fusion Puts Hearing Aid Users in the Driver’s Seat

By Tammara Stender, AuD


Most drivers keep their gaze on the windshield to see oncoming traffic. It is, after all, the best way to avoid collisions. Occasionally, however, you will check your rearview and side mirrors to monitor the road and other vehicles. Mirrors are crucial for safe driving, even though you cannot drive effectively while constantly looking at them. A quick glance in the side mirror can tell you when it is unsafe to pass another car. The rearview mirror can help locate the sound of an approaching ambulance. Accidents and reckless driving would be extremely common without these mirrors.

Many hearing aids using wireless communication are like mirrors, permitting the user to focus on the loudest speech in the listening environment. This speech signal, by communicating between devices, is amplified for the listener for the best audibility. These systems, however, often lack monitoring for other signals in the environment or, in other words, the rearview and side mirrors. Keeping the listener focused on the loudest speech signal often comes at the cost of monitoring other sounds surrounding the hearing aid user. The listener may not even be aware of other sounds present when the hearing aids are focused solely on the signal of interest. The user, for example, might not hear a friend calling from behind if his hearing aids are focused on a speaker in front of him. Hearing aids choose which signal to focus on, so users are in the passenger seat for controlling their listening environment.


An Innovative Approach to Binaural Technology

Binaural fusion is a new way to think about binaural processing in hearing instrument technology. This approach’s philosophy is that the hearing aid user should always stay in the driver’s seat and decide on the sound of interest. This technological strategy is fundamentally different from other approaches on the market that use wireless communication between binaural hearing aids, and it supports natural binaural processing in the brain. The user, not the hearing aids, is then able to determine the signal of interest. This fundamentally different approach to binaural hearing aid processing empowers users to detect sounds and listen to what they want.

Binaural fusion has its basis in human binaural processing literature, which explains how unaided listeners choose what they pay attention to in their environment. Normal-hearing listeners can detect an approaching sound from behind even when a louder sound is in front of them. Other approaches to binaural technology, in contrast, result in hearing instruments making these decisions for the user; they may automatically decide that a less-intense speech signal arising from behind the listener is not the signal of interest. Binaural fusion allows hearing instruments to work together synergistically as a single fused system designed to provide the most natural sound representation to the user. The end result is that the user has access to all surrounding sound inputs and to optimal audibility for the loudest speech signal. The hearing aid user, in other words, can choose to look in the rearview mirror while keeping his eyes on the road.


How It Works

Hearing instruments independently analyze the type and level of sounds in the environment for binaural fusion to occur, determining the location of sound sources and the signal-to-noise ratio for speech. Next, the information gathered by each hearing instrument is exchanged between them to derive a common solution for the most appropriate sound processing. This cooperative effort between the hearing aids results in the most advantageous binaural microphone response and coordinated noise reduction and gain settings for any given listening environment. The binaural fusion strategy introduces two new features: binaural directionality and binaural environmental optimizer II.


Every Microphone Configuration in a Single Hearing Aid Program

Binaural directionality provides the most advantageous microphone response for both hearing aids in a binaural fitting while preserving the user’s ability to choose the signal of interest. Every possible microphone response is offered by binaural directionality: bilateral omnidirectional, bilateral directional, and bilateral omnidirectional and directional, with the right or left hearing aid assigned a directional response based on the listening environment. Published research was instrumental in designing and determining which response would be the most natural, preferable, and advantageous in a given situation.

A bilateral omnidirectional response, for example, will be chosen in quiet environments while a bilateral directional response is selected when speech is directly in front of the listener. An asymmetric response (omnidirectional on one side and directional on the other) is chosen when speech is not directly in front of the listener in a noisy environment. The user enjoys improved speech discrimination in noise in conjunction with better listening ease and monitoring abilities for surrounding sounds by using inputs from both ears to derive the binaural microphone response. All this happens without ever having to change the hearing aid program.  


Holistic Listening Experience

Binaural environmental optimizer II utilizes wireless data transfer between hearing aids to coordinate the noise reduction and gain settings specific to the listening situation. The environment is analyzed at each hearing aid, and this information is shared between the aids to determine the most accurate classification. From this classification, the noise reduction and gain settings are optimized and synchronized for better listening comfort, audibility, and sound quality as the user encounters different environments throughout the day.


Putting the Hearing Aid User in Charge

The binaural fusion technology strategy works as a two-step process to prioritize the user’s decision-making abilities. It first enlists the hearing aids to analyze and classify sounds synergistically in the environment. The best possible amplification is then provided, without the hearing aids making decisions about what the user does and does not want to hear. It is distinguished from other sound processing strategies by its focus on user intent. With binaural fusion, the view from the windshield (the loudest speech signal) is still prioritized while the option to glance in the rearview and side mirrors is maintained. The hearing aid user is in the driver’s seat and allowed to navigate the listening environment instinctually and effectively.


Dr. Stender is a senior audiologist in the Global Audiology Group at ReSound in Glenview, IL.