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Position-Adaptive Quiet Zones in Enclosed Spaces

Setup of the ANC system in a test cabin
Block diagram of the feedforward control

In the presence of big transformers or machinery, e.g. jet engines, one is exposed to a high and especially continuous noise level. The emitted - primarily low frequency - noise is only attenuated insufficiently by means of the usually passive earmuffs. Hence, in aircraft cockpits for example, the noise of the engines is also reduced actively by using so called anti-noise. This technology is commonly known as "Active Noise Control" (ANC) and has recently also been introduced to the consumer market as noise cancelling head phones.

However, available ANC solutions are either spatially fixed or require the carriage of respective mobile devices (e.g. head phones). The aim of the recent project is to overcome these limitations. For this, an adaptive feedforward active noise control is designed that automatically creates a local quiet zone at a desired position. To realize that, the virtual microphone technique is used, combined with a camera tracking based adaption of the microphone's effective position to shift the quiet zone. At the same time, the achievable local noise attenuation essentially depends on the parametric modeling of the sound propagation paths (the control paths), which spatially vary. This is primarily due to the enclosed space acoustics, which cause sound reflections and this way affect the path identification adversely.

Contact person: M. Sc. Sven Höber