Ramola, R., Senthilkumar, G., Kannan, P., and Chennakrishnan, M., "Identification and Reduction of Whistling Noise in Passenger Vehicle," SAE Technical Paper 2014-01-2317, 2014, doi:10.4271/2014-01-2317.
The demand for comfort level in commercial vehicles is steadily increasing. Hence, fine-tuned performance parameters and attributes are required to fulfill the expectations from these vehicles. Refinement of noise and vibration without affecting performances of sub-systems and components has become extremely challenging with increasing customer requirements.This paper presents an approach to identify and reduce the high level whistling noise that was perceived in the passenger compartment while the vehicle was accelerated above 50 kmph. Interior noise measurements in static engine run-up condition reveal that the whistling noise is of specific order. Since, whistling noise is related to aerodynamic response of components, engine cooling fan, turbo charger, alternators and compressors were suspected. Using order tracking and near field measurements, HVAC alternator was confirmed as the main cause for whistling noise.Noise measurements confirmed that orders related to alternator cooling fan became dominant above 50 kmph. HVAC alternator was tuned in a manner to reduce the noise without affecting the electrical performance. Significant reduction in whistling noise level was observed in both objective and subjective assessments in the passenger compartment with this modification.