Measuring hearing aid compression algorithm preference
One of the key mechanics in hearing aid algorithms is compression. The human ear is capable of processing sounds with a wide range of intensity levels. Hearing impairment mostly impacts the sensitivity to soft, low intensity sounds. Using Wide Dynamic Range Compression (WDRC), modern hearing aids are able to enhance soft sounds by applying more gain in comparison to the amount applied to loud sounds. This results in a better audibility of somebody speaking softly without making high intensity sounds unpleasantly loud.
The effectiveness of a hearing aid depends on a great number of factors: Preferences of the hearing aid wearer, characteristics of the hearing impairment, aspects of the compression algorithm (ratio, fast/slow, threshold) and the acoustic properties of the sound environment (cocktail party, noisy street or a church with strong reverb). What better way to tune a hearing aid to the wants and needs of somebody with a hearing impairment than to test it in real-life situations, and make adjustments on the fly? In the last decades, the vast improvements of hearing aids have been predominantly based on lab-experiments. Nowadays, there is also a great potential in testing hearing aids in real world situations.
Jennifer Lentz, Donghyeon Yun and Stuart Smiley of Indiana University aim to do just that. For their research they plan to fit test subjects with the Tympan as a hearing aid and test platform. They have developed an application for Tympan that runs a WDRC algorithm and at the same time records samples of the incoming signal to measure the acoustic properties of the environment. All the while, the test subject can also change between algorithm settings, and take notes on the Smartphone app about the environment, the target sound and the performance of the hearing aid. In this approach the Tympan simultaneously tracks information about the hearing aid settings, changes in the acoustic environment and user preferences. Hopefully, this will provide valuable insights into the complex relations between those factors and contribute to further improvements of hearing aids.
A preliminary version of the app is now complete and the team is ready for testing. They plan to give the subjects some training in using the Tympan and smartphone app, and ask them to wear the Tympan for 1-2 days (8 hours a day). During this time they will listen to different algorithm settings in different environments and take notes. In this first research stage it is important to evaluate the practical aspects of this test-setup: how do the subjects feel about wearing the Tympan and using the app? How does the subjects’ ability to control the loudness affect the experiments?
After sorting out these teething problems, the opportunities of this setup will be endless. What’s next on the researchers’ agenda will without a doubt be interesting.
About the TYMPAN ASA2021 Design Challenge
During the ASA (Acoustical Society of America) conference in June 2021, Tympan hosted a design challenge: What is possible with the Tympan?
10 exciting new applications were submitted and presented at the following ASA conference: Enhancements of hearing aids, spatial acoustic processing and smart earphones and much more. Stay tuned if you want to learn what is possible and to keep track of future developments.