Robot-controlled acoustic holography helps hearing aid development
“The big challenge in hearing aids is to have high gain and to have that, you need to be able to control your feedback," said Poul Kristensen, Senior Acoustic Engineer at GN ReSound. "It’s a very small device for gain that is sometimes up to 80 dB, so you need many different tools to understand the feedback patterns.”
In hearing aids there are different vibration-borne feedback patterns, meaning the small speaker inside generates high pressure sound that makes the whole device vibrate. This vibration generates sound and if the sound path from the speaker to the output is not insulated you can also have direct sound feedback. For development prototypes this is especially important.
GN ReSound needed a systems that could provide accurate conformal mapping on the small scale that they were looking for – and do so automatically and unattended. A Statistically Optimised Near-field Acoustic Holography (SONAH) system had been developed for another customer by the Customised Project Department of audio specialist Brüel & Kjær, and this was used as the basis of the new system.
“At the time we were looking for a system it was taking an unpredictable amount of time in Research and Design to get the device performance and gain that we were looking for, because the feedback pattern is so difficult to understand,” said Kristensen. “We had to do a lot of experiments without seeing the whole picture, so it took us a long time and the time taken wasn’t predictable. We wanted to get into a situation where things were more predictable, with a better understanding, so we could be more professional with better tools. This was one of the tools to build up our simulation models and understanding.”
Brüel & Kjær is a subsidiary of UK-based Spectris which has annual sales of £1.1bn and employs around 7,500 people worldwide across its four business segments
www.bksv.com
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
