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Master-Vortrag: Active Noise Cancellation Algorithms for Headphones and Hearing Aids in Time Variant Environments
Christopher Durand
Montag, 28. Mai 2018
11:00 Uhr
Hörsaal 4G
Acoustic noise is a relevant problem in everyday life. It causes stress and even more severe health problems. Passive sound isolation is often used as a measure against noise. However, for low frequencies the attainable amount of isolation is rather limited and requires large and heavy absorbers. With the advent of modern electronics, active systems are increasingly used to counteract unpleasant acoustic noise. Active noise cancellation systems reduce disturbances by creating a phase-inverted anti-noise signal.
Today portable solutions are available with noise canceling headphones. Commercial systems often rely on fixed controllers which do not achieve an optimal performance in complex scenarios. Therefore, adaptive systems have to be employed, which adjust to specific noise conditions.
Implementing both high-performance and robust ANC systems is a considerable challenge. When the cancellation signal is played back, it propagates along an electro-acoustic transfer path, called the secondary path. It introduces amplitude and phase distortion on the cancellation signal. Therefore, the secondary path has to be estimated to create an exactly matching control signal. If the secondary path model significantly differs from the real path, for example when the fitting conditions of a headphone change, adaptive systems may get unstable. This thesis focuses on robust on-line secondary path modeling for adaptive noise control. Furthermore, direction-of-arrival dependencies of noise cancelling headphones are investigated.
