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Evaluation of different hearing aid couplings in every day life with Ecological Momentary Assessment
One of the biggest challenges for hearing impaired people is understanding speech in noisy environments. What may help them are hearing aids with state-of-the-art noise reduction and directional microphone systems. The benefit of these algorithms is biggest when using a closed coupling where little direct sound mixes with the amplified sound. Also, in comparison to open couplings, closed couplings can provide more gain at high frequencies due to better feedback stability. These two factors both help to improve speech understanding. On the other hand, occlusion effects may occur, and patients may perceive their voice as being too loud and too boomy. Thus, open coupling is often preferred and in fact about two thirds of all fittings of Signia hearing aids are done with an open or semi-open coupling.
Here we investigated how the satisfaction of hearing aids compares for different couplings in everyday life. Subjects were fitted with Signia Pure 13 Nx hearing aids and open domes, closed click sleeves and click molds with a vent of 0.8 mm. Each coupling was tested for one week at home and in randomized order.
We used the method of Ecological Momentary Assessment (EMA). This makes sure we cover all relevant situations in every day life and answers are not distorted by memory biases. Also, this method is very context sensitive allowing us to analyze a number of different situations separately. Subjects were provided with mobile phones which prompted them several times a day to fill out a questionnaire. In addition, they had the possibility to fill out a questionnaire whenever they wanted.
So far eight experienced hearing aid wearers with mean age 72,8 years (std: 5.6 years) participated in the study and filled out in total 1226 questionnaires. Subjects had a mild to moderate hearing loss with a mean pure tone average of 47.5 dB (std: 6.6 dB).
Preliminary EMA results suggest that the majority of subjects reported significantly better speech understanding with closed couplings. This is consistent with the result of the Göttinger sentence test in noise. Nevertheless, satisfaction ratings pooled over all questionnaires indicate that most subjects prefer open couplings to closed ones. However, satisfaction is situation dependent. Open couplings are preferred when listening to music or not actively listening to anything. If the background is quiet and not distracting from or adding anything to the target sound source, closed couplings are preferred.