Silence is golden - Implementation of a noise cancelling office chair

Elevated noise levels are commonplace in today's office environment and may compromise attention and work performance or even affect health. This work aims at reducing acoustic immissions by integrating an active noise control feature into an office chair. To obtain a reasonable noise cancellation, several challenges have to be considered. First, noise cancellation has to be achieved at the user's ears (virtual microphone), rather than at the noise measurement location (physical microphone). This requires estimating the noise at the virtual location, which is generally referred to as virtual microphone algorithm. Second, head movements of the user as well as the position of the noise source have to be detected. Third, all mechatronic parts should be integrated into the chair, ruling out the use of a reference microphone. This paper describes the necessary measurement techniques and algorithms to implement a noise-cancelling office chair. To achieve adequate noise cancellation, stereo operation with two actuators is advisable. Different stereo algorithms are examined. A measurement principle based on ultrasonic sensors as well as the inherent algorithms to detect the user's head position are described. Finally, this paper describes the implementation of the concepts in experiment and simulation and provides results describing the achieved performance.