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Individualized Binaural Diagnostics and Technology

Periodic Reporting for period 2 - IBiDT (Individualized Binaural Diagnostics and Technology)

Reporting period: 2019-07-01 to 2020-12-31

360 million people worldwide have some form of hearing loss, 10% of them children. While hearing aids and cochlear implants reasonably restore the hearing with the ear they supply, they do often not restore two things that normal hearing listeners take for granted: 1) Being able to localize a sound source in space and 2) being able to understand a conversation partner even in the presence of more intense competing talkers and other sound sources. Both of these abilities have been shown to contribute to the quality of life.
A sound arriving from a certain direction in space (e.g. off the midline) arrives at the two ears at slightly different times, generating an interaural time difference (ITD). In addition, the head attenuates the sound at the ear opposite to the sound source to produce an interaural level difference (ILD). Brainstem circuits are specialized in detecting ITDs and ILDs with a temporal precision unique within the nervous system. As soon as one or two hearing aids or cochlear implants are applied to the ears, any difference in their sound processing corrupts the interaural differences, reducing the binaural advantage. Further, a fair number of people that are said to be “normal hearing” in clinical terms does not get the “normal” advantage of listening with two ears – binaural hearing. This includes particularly people with a neurologic history, such as a stroke but can also happen in completely healthy individuals. To date hearing researchers can list many factors that may limit the binaural benefit. However, due to the complexity of the auditory system (a complex inner ear followed by an even more complex brain), they have only a limited understanding in which way and in which situation a certain pathology corrupts binaural hearing. Hearing devices are far from employing such causalities for optimizing algorithms to the specific pathology.
The objective of the project is therefore to better relate neurophysiology and pathophysiology to normal and impaired perception. This is done by developing a detailed computer simulation of the auditory system validated through a broad range of listening experiments. Once we are confident that we know the pathology of an individual we can then simulate this impairment and see when and how it causes the most extreme and maybe a unique problem. More though, we can develop algorithms, similar to those in hearing aids, but specific to the pathology, optimize them with the simulation and test them with the patient. If the patient shows the same improvement we have predicted in our simulation, we have not only helped the patient but demonstrated that our novel approach can potentially help hundreds of thousand people to improve their binaural hearing and hence their quality of life. Our team is thrilled to pioneer this approach and hope to trigger many follow-up studies.
The computer model of the normal hearing auditory system has been developed and is currently extended and optimized. The first part has been published and successfully applied to three published datasets – in combination more than 1000 different stimuli.
A study investigating spatial hearing with stroke patients has been designed and experiments will start as soon as Covid-19 regulation allow.
At an early stage of the project we showed that subjects with two cochlear implants can have improved sound localization when we artificially increase the differences between the two ears.
A new model-steered measurement design is currently being developed. After each response from the test subject our newly developed system predicts on-line with which next test condition we learn most about the pathologies. This approach has the potential to revolutionize auditory experimentation as well as audiologic diagnostics. We expect that the new method will result in improving time efficiency by a factor of two, if not more. It is not expected to be applicable in all situations and with too complex models.
Our model is going to be the first of its kind in being physiologically realistic and being able to account for psychoacoustic data in normal hearing subjects. Upcoming experiments will be conducted in a revolutionary paradigm: Rather than testing pre-defined stimuli and then see if the data has diagnostic value, we will put the diagnosis in the experiment loop and measure where its optimal in terms of diagnostic value. Featuring a large-scale longitudinal study with stroke patients we expect to identify distinct sound localization and discrimination problems and relate them to the respective lesion. We will develop spatial remapping algorithms that are expected to provide a better spatial hearing for some or many of these patients and we will further individualize our binaural algorithms for cochlear implant users.