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Active Noise Reduction in Headsets

Especially in case of low-frequency noise, passive hearing protection can be seen as insufficient. So-called ANR Headsets (ANR: Active Noise Reduction) increase the passive noise attenuation using active control. Nevertheless, the reduction performance of commercially available ANR Headsets is perceived as insufficient in high level noise surroundings. Therefore, in cooperation with the company Sennheiser Electronic the project COMDAC was initiated. The objective of the project was the development of a digital adaptive ANR communication headset with an increased noise reduction performance. The research at our institute was focused on the identification of the system and the controller design. The controller is designed using non-adaptive control techniques in combination with an optimal adaptive filtering concept. The developed prototype of the ANR Headset is shown in the figure.

Contact person: Dr.-Ing. Christian Pape

Reduction of the engine noise in motor vehicles through adaptive regulated compensation

In this project a new control engineering system was developed, which compensates the engine noise in motor vehicles using active sound compensation.

The principle of the sound compensation is based on the production of a compensation sound by 180± out of phase to the engine noise. This compensation sound must have the characteristic to eliminate pressure maxima of the engine sound with pressure minima of compensation sound. This compensation sound can be produced from several loudspeakers (music loudspeakers) in the passenger compartment.

This ANC system (Active Noise Control) is based on the Fourier analysis of the engine noise into rectangular signal elements. Through the characteristic of the orthogonality, single dominant engine noise elements could be regulated individually.

By means of experimental attempts in a motor vehicle it was shown through order analysis and spectrograms, that this new system demonstrates a very high degree of compensation. This feature is to attribute to the fact that a discrete I-controller was used. This type of automatic controller avoids remaining controller deviations in the stationary operation.

Contact person: Dr.-Ing. Christian Pape