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Samples - Better speech recognition for people with cochlear implants

Cochlear implants greatly improve the quality of life for severely hearing-impaired people. However, understanding speech in noisy conditions remains a challenge. Scientists from the University of Leuven (Belgium) and market leader Cochlear are developing software that improves signal processing in cochlear implants, enabling better speech recognition.


Many of us don’t ever think about it – but our natural auditory abilities are actually rather remarkable. When we are talking to friends in a noisy bar, with music and chattering in the background, we are able to filter out the sounds that we need in order to understand the conversation, and ignore the noise. When listening to an orchestra, we can recognize the sounds of many different musical instruments playing at the same time, and appreciate the richness of their combined timbre. For people with hearing loss, this skill is not so natural. Even when they are using a hearing aid or a cochlear implant (CI) – a hearing device placed surgically into the inner ear – the fine nuances of sound perception lie beyond their reach.


“Some major technological improvements have been made over the past decade,” says professor Jan Wouters at the University of Leuven (KU Leuven). His aim is to improve the performance of CIs. “The first generation of CIs merely allowed people to hear basic sounds, and only in a quiet environment. Today’s implants are much more sophisticated, even allowing people to have phone conversations.” But improvements are still dearly needed, he stresses. The quality of ‘artificial sound’ is still not approaching that of natural sound, and people with CIs still face severe limitations.


Together with the CI market leader Cochlear, Wouters and his colleagues are developing software that improves the processing of sound signals that are transmitted to the inner ear. To be able to describe the added value of this technology, Wouters first explains how a CI works. A CI, he indicates, will help a person who has a functional auditory nerve, but who has a problem with the hair cells that convert sound vibrations into neural signals. These hair cells are found in the cochlea, the spiral-shaped space in the inner ear. The CI directly stimulates the auditory nerve, thereby bypassing the middle ear and hair cells. The electrodes receive their information wirelessly from a processor with microphones, worn behind the ear.


“In this process,” says Wouters, “much of the sound information is lost. Speech and music are incredibly complex, and certain cues in those signals are lost during signal processing in standard CIs.” That is why speech sounds rather metallic to a person using a CI, he elaborates, and why much of the magic of music is ‘lost in translation’. “Our challenge is to design mathematical models that describe acoustic signals in as much detail as possible,” says Wouters, “and to apply these models in software that turns this acoustic information into electrical signals.”


Wouters and his colleagues had already been collaborating with Philips Hearing Implants for many years when this division was taken over by Cochlear twelve years ago. Cochlear is an Australian company with a research and development department in Belgium. It serves around 70 percent of the CI market worldwide. The two institutions are cooperating closely – to the benefit of both, according to Bas van Dijk, global research coordinator ‘sound coding’ at Cochlear. “The KU Leuven conducts its research at a much more fundamental level than a company would do,” he says. “You never know which elements of the research will find their way into market applications – but when they do, they lead to remarkable technological improvements.”


As an example, he names the main invention that originated at the KU Leuven and that now serves 26,000 new cochlear implant recipients each year: a so called beam-forming algorithm. This mathematical procedure selectively amplifies sounds coming from the direction in which the person is looking – which are likely to be the sounds that he or she wants to focus on. This is a major improvement in everyday conversations. “People who are using older systems can usually get an upgrade of the external part of their device,” says Van Dijk, “which allows them to benefit from the new technology.” Worldwide, over 250,000 people are using Cochlear’s devices, he underlines, and this number is increasing rapidly.


Jan Wouters highlights another advantage of the collaboration between the KU Leuven and Cochlear. “At the university we bridge the gap between lab and clinic,” he says. “First of all, due to our medical contacts here at the university we are well aware of the relevant clinical questions. Secondly, once we have moved from mathematical models to signal processing to audiology, we need to test how a patient experiences these changes. We conduct so-called psychophysical tests with patients in our lab to establish which elements of signal transduction actually determine the quality of sound and the intelligibility of speech. Once we have tested these effects and adjusted the technology where needed, we can transfer it to the company to be further developed.”


Bruno Lambrecht, legal advisor at the KU Leuven, is the technology transfer officer involved in the collaboration. “For the very first project, we negotiated the terms and conditions of the collaboration,” he says, “and we have been able to reuse that frame for several subsequent projects, which is somewhat of a luxury position.” This is possible, he adds, is because the scientists have convincingly proven their added value to the business, and vice versa, which creates a high level of mutual trust. “This is absolutely crucial for any long-term collaboration.”


Cochlear, as Lambrecht explains, holds all patents and intellectual property rights associated with the shared inventions. “A global market leader requires patent control in order to respond adequately to the market,” he explains. The company pays the university an agreed fee per shared project and a ‘reasonable compensation’ when a concrete invention is applied in Cochlear’s devices. In addition, the collaboration receives funding from the Flemish government because of its fundamental research component. Lambrecht: “Companies are usually not very interested in fundamental research when the outcomes are unclear. This is why the support from the Flemish government makes a difference. All parties benefit. We call it the ‘triple helix’: academia, business and government work together, paving the way for truly innovative technologies.”


Based on their main challenge of improving signal transduction, the KU Leuven and Cochlear are now collaborating in three-year projects that address separate areas of potential improvement. “We continue to improve the suppression of background noise,” says Wouters, “and we are looking for ways to improve sound perception for people who use a CI on one side and an external hearing aid on the other side.” Another ambition, as both Wouters and Van Dijk point out, is to develop objective ways to determine the correct settings for the device, for instance in the case of children who are too young to describe what they are hearing. Wouters: “What we are doing touches directly upon people’s quality of life. I have received many emails from patients all over the world, telling me how much better they can hear today. For me as a scientist that is immensely satisfying.”



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Name product:Software to improve sound processing of cochlear implants, enabling better speech recognition

Research Institution:KU Leuven – University of Leuven, Belgium (departments of Experimental Otorhinolaryngology and Electrical Engineering)

Marketed by:Cochlear

On the market since:Cochlear implants since early 1980s; KU Leuven’s technology incorporated since 2005

Noteworthy:Cochlear is developing implants that receive their signals directly from TV or cell phones via bluetooth



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In the spotlight:

Hearing loss

Hearing loss – also known as hearing impairment, or (partial) deafness – is quite common in the general population. An estimated 0,2 to 0,4 percent of babies are born hearing-impaired. Hearing loss can also occur later in life, as a result of ageing, exposure to noise, head trauma or disease. An estimated 20 percent of all adults experience some level of hearing loss, and this percentage rises to 30-50 percent among people over 65.

Many hearing-impaired people benefit from hearing aids. Conventional hearing aids merely amplify the sound that reaches the ear, and thus require at least some functionality along the entire auditory pathway. If the hair cells of the inner ear are lacking or damaged, however, amplification will not be helpful. Cochlear implants fill that gap: by directly stimulating the auditory nerve, they bypass the hair cells. A variant is also available for people who lack a functional auditory nerve. This implant works much like a cochlear implant, only it transmits its electrical pulses directly to the auditory part of the brain itself.

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