Microphone array system for speech enhancement in a motorcycle helmet
Blekinge Institute of Technology, School of Engineering, Department of Signal Processing2005 (English)Report (Other academic)Alternative title
Mikrofon array system för talförbättring i en motorcycle hjälm (Swedish)
In this report a real case study of the sound environment within a helmet while driving motorcycle is investigated. A solution to perform speech enhancement is proposed for the purpose of mobile speech communication. A microphone array, mounted onto the face shield in front of the user's mouth, is used to capture the spatio-temporal properties of the acoustic wave ¯eld inside the helmet. The power of the spatially spread noise within the helmet is small when standing still while it may heavily exceed the power of the speech when driving at high speeds. This will result in dramatically reduced speech intelligibility in the communication channel. The highly dynamic noise level imposes a challenge for existing speech enhancement solutions. We propose a subband adaptive system for speech enhancement which consists of a soft constrained beamformer in cascade with a signal-to-noise ratio dependent single microphone solution. The beamformer make use of a calibration signal gathered in the actual environment from the speaker's position. This calibration procedure e±ciently captures the acoustical properties in the environment. Evaluation of the beamformer and the single microphone algorithm, both as either parts by them selves and as a cascaded structure, together with the optimal subband Wiener solution is presented. It is shown that a cascaded combination of the calibrated subband beamforming technique together with the single channel solution outperforms either one by it self, and provides near optimal results at all noise levels.
Place, publisher, year, edition, pages
Blekinge Tekniska Högskola Forskningsrapport, ISSN 1103-1581 ; 5
Speech enhancement, Beamforming, adaptive filtering, subband filtering
IdentifiersURN: urn:nbn:se:bth-00272Local ID: oai:bth.se:forskinfo40E24875FE4FD6E2C1256FFC00309C53OAI: oai:DiVA.org:bth-00272DiVA: diva2:838142