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Powertrain Component Noise Testing and Evaluation

Project Brief

Intensified competition among automakers has led to a continual redefinition of noise, vibration and harshness (NVH) benchmarks during the past few years. This has led to a new emphasis on addressing the root causes of noise and vibration generation, as opposed to the previous emphasis on noise insulation and vibration isolation.
 

Gabor transform showing the fundamental frequency and harmonies for a 13-vane variable displacement automatic transmission pump at 2,500 RPM. Click image to enlarge.

Southwest Research Institute (SwRI) has capabilities to conduct noise testing and analysis of most powertrain components over the range of 200 Hz to 20 kHz. Phase- and frequency-matched precision microphones are used to acquire the audio signal. Their frequency response is flat to within 1 dB above this range. The signal is converted directly to digital format (16-bit resolution), with no intervening analog recording process, at a sampling rate of 51.2 kHz. The signal-to-noise ratio of the system used exceeds 90 dB, and THD is ≥ 90 dB.

 
In addition to the traditional Fourier transforms and spectrograms used for noise data analysis, SwRI has software capable of performing the Gabor transform, which is generally capable of higher resolution than the conventional Fast Fourier Transform (FFT) method. The transforms can be order-tracked to facilitate root cause noise generation analysis. The audio signal may also be analyzed comparatively in the time and frequency domains to determine if a signal is multi-component, for example.

 
Powertrain component vibration tests are conducted at SwRI on dynamometers to simulate operating profiles under controlled, repeatable load conditions. Specific environmental conditions may also be controlled at the customer's request. Data are obtained from accelerometers at the component mounting points and other key locations as necessary. Many of the same data analysis methods applied to noise analysis are applied to vibrations as well to determine root causes.

For more information about drivetrain engineering capabilities and past project briefs at SwRI or how you can contract with SwRI, please contact Douglas Fussner at dfussner@swri.org or (210) 522-3972.  

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

August 05, 2008