by Neil Bauman, Ph.D.
© January, 2014
One of the most common complaints among hearing aid wearers is that hearing aids don’t work well in noise—that they pick up all the racket around us so we can’t hear (and understand) the person we are talking with.
This is slowly changing. Noise-canceling microphones have helped. So have directional microphones.
Now researchers are taking this one step further and are developing beam-forming technology that uses the microphones from both hearing aids to create a beam that focuses on the sounds we want to hear, thus essentially reducing the background racket.
According to researchers at The Hearing Cooperative Research Centre at the University of Melbourne, Australia, “Trials have shown that the technology, which will be integrated into hearing devices, can boost the wearer’s ability to hear speech in crowded cafes and restaurants by 50 per cent.” (1)
If this technology works as well as predicted, it could give super-hearing to people with mild-hearing losses. According to Dr. Harvey Dillon, “Someone with a mild hearing impairment with this device will probably be hearing better than normal; turning a device that indicates a disability into something that is supernormal”. (1)
The super-directional beamformer works by combining the output of two microphones on each side of the head. This allows the wearer to tune into the person he is talking to, while, at the same time, reduce sounds coming from other directions.
Trials in an anechoic chamber “have shown that this technology can provide listeners with a 4 – 8 decibel advantage, which is more than double that of conventional microphones.” (1)
Even though it is still in the early stages of development, if all goes well, this patented technology will hopefully find its way into the next generation of hearing aids and cochlear implants.
So much for the hype. Now let’s consider some realities before you get carried away thinking you’ll finally be able to hear perfectly in noise with your hearing aids. The key here is that you’ll probably “hear better” than you do now with current technology in hearing aids, but it won’t let you hear well in any noisy situation with your hearing aids alone. There are several reasons for this.
First, we can only hear as well as our damaged ears allow us to hear—so we may never hear as well as a person with normal hearing—no matter how much noise is removed.
Second, we need a minimum of 15 dB signal-to-noise ratio in order to understand speech, and better yet, a 25:1 signal-to-noise ratio. This fancy new technology is aiming at a 4 to 8 dB increase in the signal-to-noise ratio above what hearing aids are doing now. This is a step in the right direction to be sure—but that amount of increase in the signal-to-noise ratio is still not the complete cure for hearing in noise.
Obviously if the signal-to-noise ratio in a given situation was say 10:1, then adding 4 to 8 dB would give 14:1 to 18:1 and we should be able to understand speech. However, if the signal-to-noise ratio was very poor, say 2:1, then we’d still be unable to extract clear speech from all that racket.
Third, we can already hear well in noise if we use assistive technology. In fact, with the assistive technology available today, we can often hear better than people with normal hearing when noise and distance are involved as long as the microphone for the assistive device is at the speaker’s lips.
Hearing aids, no matter how good the microphones are, will never beat assistive technology in this respect. This is just the laws of physics in action. Sound signals degrade in air, but not in the technologies used in assistive devices. Therefore, we will always have an advantage if we use assistive devices properly.
The downside to using assistive devices is that we have to lug around extra “stuff” in order to make this happen, and this is not always convenient.
Therefore, when this new technology is incorporated in new hearing aids sometime in the future, expect to hear better, just don’t expect it to give you normal hearing.
(1) van den Berg, Lucie. Sept 25, 2013. “New technology to help hearing-impaired“. Herald Sun.