New wireless microphone systems enabling hearing impaired people to pinpoint exactly where sounds are coming from could soon improve their listening experience in classrooms and conference rooms.
In the hubbub of a classroom or an auditorium, it can be difficult for a person who is hard of hearing to pick up everything a teacher is saying, even with a hearing aid. A major reason for this is the difficulty in identifying the exact location of the source of sounds.
To help solve this problem, a team of researchers from École Polytechnique Fédérale de Lausanne (EPFL) has developed a new system of wireless microphones that enable the wearer – even with closed eyes – to locate the speaker in a room. This feature substantially improves the listening experience. The researchers have developed two prototypes with support from the Swiss Commission for Technology and Innovation and in partnership with the company Phonak Communications AG.
A smarter system
A person with normal hearing automatically localises the source of a sound, thanks to the way sound arrives at each ear in a slightly different manner and not at the exact same time. However, these subtle nuances are not transcribed in conventional systems with wireless microphones. This means it’s impossible for people who are hard of hearing to pinpoint the source of a sound, and this diminishes the listening quality.
The EPFL researchers have found a way to configure the transmitted sound in each ear to artificially recreate the natural feel of listening, in the context of a classroom or audience.
Their prototype consists of hearing aids and wireless microphones. The system is made up of two conventional hearing aids, with a microphone on each, and a computing system tailor-made for localisation and spatial information. The hearing impaired person wears the inter-connected hearing aids. The speaker wears a clip-on microphone connected to a wallet-size box that transmits the voice via radio waves, which travel about 900,000 times faster than sound waves.
“The built-in microphones in the hearing aid get the sound the moment it arrives, which is different for each ear,” says Hervé Lissek, who leads the research. “We record both the sound received off the microphone, which is offset, and the sound transmitted via radio waves, which is homogeneous in both ears. This information allows us to deduce, via an algorithm, the position of the speaker and then to alter the sound accordingly”.
Lissek’s PhD student Gilles Courtois adds: “The localisation of sound in space is then simulated by playing with the phase, amplitude and intensity of the transmitted sound in each ear.”
Added comfort and comprehensibility
The technology falls within the range of Roger products that are sold by Phonak, intended to be used both in traditional schools and in special schools for hearing-impaired children, but also for adult with hearing loss. In the classic version, the voice of the teacher is recorded by the microphone and transmitted uniformly to both ears, destroying any notion of spatiality. The new solution therefore brings genuine added value in terms of comfort and comprehensibility.
A paediatrics hearing care professional, Philippe Estoppey, who implements 30 to 40 hearing aids in Swiss classrooms, welcomes the innovation. “It is all the more interesting if more than one teacher is speaking,” he says. “To hear a speaker correctly in a room, the first thing we do is to locate him or her. The body expression and the movements of the lips are helping in terms of intelligibility.”
For the developers, the next step is to work on a final version of the device. “In the end, the system will be fully integrated. We will use the standard microphones of the hearing aids, and the processors of the prosthesis will make the calculations,” says Yves Oesch, project manager at Phonak. “We are quite pleased with the results of this project. We now hope that we can continue working with EPFL towards the objective of marketing this new product in the future.”
– Adapted from EPFL Mediacom