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In this article, Claus Elberling takes us through his journey that led to the discovery of the CE-Chirp®.
In 2003, Interacoustics launched the Eclipse. A powerful combination of ASSR, ABR and OAE that is still considered state-of-the-art. One of the new technologies used in the Eclipse was the CE-Chirp®.
In 2006, Claus Elberling, M.Sc.E.E., D.Sc.M., Honorary Senior Scientist at the Interacoustics Research Unit (IRU) and former Head of Eriksholm Research Centre, along with other leading scientists, developed the CE-Chirp®. He was drawn to find a solution to the well-known problem of small ABR response amplitudes, which can make it difficult to determine hearing thresholds.
We asked him about this revolutionary development and why it is still so important when doing ASSR recordings.
I first became aware of the concept of the Chirp when I read an experimental paper back in the 1980s. About 15 years later the Chirp surfaced again in a couple of important papers by Torsten Dau (professor of Hearing Sciences at the Technical University of Denmark).
In 2004, we found a need to improve the ASSR-testing of newborns and focused our attention on two areas: (1) improving the stimulus, and (2) improving the response detection. To improve the stimulus, we took a close look at the Chirp concept. We developed and applied the underlying mathematics on a large amount of electrophysiological data that described the conditions in the normal, human cochlea – and the CE Chirp® was born.
The CE-Chirp® attempts to synchronize the electrophysiological responses from the different frequency bands in the normal cochlea and the corresponding brainstem centers.
The compound response, which is recorded by electrodes on the surface of the scalp, combines the responses from all frequency bands involved. Due to the synchronization, the compound response will increase significantly in magnitude.
The electrophysiological responses that are recorded from surface electrodes are very minute electrical responses – in the order of 1/10 of one millionth volt. Any increase in response magnitude will therefore shorten the recording time and improve the quality of the response waveform.
Especially in newborns, a short recording time is of paramount importance and a higher response quality will improve the certainty of the diagnostic application.
Together with later developments, for instance the Narrow-Band CE-Chirp®, the Level Specific CE-Chirp® and the Advanced Response Detection Algorithm, the CE-Chirp® has turned ASSR-testing into an acknowledged clinical test routine and the Eclipse into the most attractive electrophysiological test equipment.