Recent Publications Wiggins IM, Seeber BU (2012) Effects of dynamic range compression on the spatial attributes of sounds. Ear and Hearing, in press Kerber S, Seeber BU (2012) Sound localization in noise by normal-hearing listeners and cochlear implant users. Ear and Hearing, in press Wiggins IM, Seeber BU (2011) Dynamic-range compression affects the lateral position of sounds. Journal of the Acoustical Society of America 130(6), 3939 [PubMed] [DOI] Viola FC, Thorne JD, Bleeck S, Eyles J, Debener S (2011) Uncovering auditory evoked potentials from cochlear implant users with independent component analysis. Psychophysiology 48(11), 1470-80 [PubMed] [DOI] Kerber S, Seeber BU (2011) Towards quantifying cochlear implant localization performance in complex acoustic environments. Cochlear Implants International 12 Suppl 2, S27-9 [Open Access Article (UKPMC)] [PubMed] Seeber BU, Hafter ER (2011) Failure of the precedence effect with a noise-band vocoder. Journal of the Acoustical Society of America 129(3), 1509-1521 [DOI] Seeber BU (2011) The contribution of intrinsic amplitude modulation to the precedence effect at high frequencies. From Becker-Schweitzer J, Notbohm G (Ed.), Fortschritte der Akustik - DAGA 2011 View all publications from this research group
Participants are wanted for a study of hearing in noisy places - click here for more information.
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Cochlear implants are the most successful sensory prosthesis – often they can give deaf patients the ability to understand speech and with it to naturally communicate with spoken language. Children given cochlear implants at a young age can learn to speak and in some cases may be even able to attend mainstream schools. It is thus no wonder that some describe cochlear implants as a “miracle cure” but one should not forget that patients remain deaf without their devices. This becomes painfully apparent to patients when it comes to understanding speech in the presence of other sounds – this is very difficult or even impossible. The reasons for this lie in the way cochlear implants currently work: cochlear implants replace the function of the inner ear by stimulating the hearing nerve with electric pulses, in principle similar to what the functioning inner ear does. However, the hearing nerve has roughly 30000 nerve fibres to transmit information to the brain while the cochlear implant has only a small number of electrodes, usually 12-24. Individual nerve fibres can thus not be independently stimulated by the implant. To name just one other limitation: it is not known when to place an electric pulse to best transmit the fine timing code that exists in the hearing nerve. We are trying to understand the impact this has on hearing in noisy places and how to overcome the existing limitations in several different ways.
Figure 1. The anechoic chamber
When two persons speak, words rarely come at exactly the same time. Timing similaries help us identify which information belongs to a certain speaker. We study whether and how patients can use the similarity of the time information in the sounds to improve hearing one sound in the presence of other sounds.
Binaural hearing, listening with two ears, is very useful for getting an idea of our surroundings, alerting us to danger and helping us to understand speech in noisy environments. Until now, most cochlear implant patients have only had one implant, but having two may offer advantages although at the same time it presents new challenges to science. At present, having two cochlear implants does not provide many of the benefits that binaural hearing does to people with normal hearing. One part of our work is concerned with simulating listening with two cochlear implants in order to understand current limitations and develop more effective devices.
Locating where sounds come from relies on comparing the information from both ears. In quiet this may well be possible with cochlear implants. However, in rooms, sound is reflected from walls, the floor, windows and so on and these reflections mix with the original sound. The healthy auditory system has the capability to perceptually suppress reflections, making sound localisation in rooms possible despite the reflections. We therefore are studying the mechanisms that help normal hearing people separate the direct sound from reflections and why they fail with cochlear implants. Understanding the underlying mechanisms will help to improve processing strategies in future cochlear implants and help hearing impaired people better cope in difficult listening situations.
For our studies we have developed a unique setup which allows us to play multiple sounds from different directions. It is hosted in a laboratory in which walls are covered with foam to suppress sound reflections. By playing artificial reflections of the sound from loudspeakers we can simulate arbitrary rooms in this laboratory – and place the patient from one moment to another in a different room without even getting up!
We are interested in how children learn to locate sounds during their first few years of life because it will give us insight into the brain processes for sound localisation. We have extended our laboratory setup with video projection and motion tracking technology to develop a game like task to study a child’s ability to locate sounds and what aspects of the sound they use to locate it. Using this game task we hope to test children over a wide age range and also children with a range of hearing difficulties.