Improvement of an objective rating for turbocharger tonal noises

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Improvement of an objective rating for turbocharger tonal noises

Gaude, Gladys / Lamotte, Lucille / Lefevre, Thierry

Subjective evaluations to quantify noise in a vehicle can be questionable and sometimes not reliable. A method based on microphone measurements has been developed to quantify the annoyance of turbocharger tonal noises in a vehicle. Psycho-acoustic parameters are used to quantify the annoyance; the most important of them is the prominence of the tone itself from the background noise, called Tone To Noise Ratio. The high acceleration rate of turbocharger requires an extraction of the exact frequency of the tone and a robust signal processing technique. This paper presents some solution to these issues. First, the exact frequency of the tone is extracted from vibration measurements of the turbocharger. Then, three different tracking techniques have been studied: Fast Fourier Transform, Pseudo Smoothed Wigner- Ville Distribution and Vold-Kalman filter. Finally, the number and the spatial position of microphones in the vehicle have been optimized. With these solutions, the rating has been updated and validated using a database of 300 tested vehicles. A Software dedicated to turbocharger noises has been developed and provides an Objective Quotation for all turbocharger tonal noises in 2 key driving conditions.