Automotive HVAC Induced Blade Passing Frequency (BPF) Tone and its Suppression 2013-01-1915
Audible tones in vehicle interiors are undesirable because of their impact on customer satisfaction and quality metrics. Most of the loudest tonal noise sources located in the engine compartment are isolated from the vehicle interior by the dash-wall. A majority of the automotive blower/s are located in the vehicle interior in the close proximity of the driver and passengers. Hence, the blower induced tones (if present) become audible and airborne, they readily propagate to the vehicle occupants. The severity of these audible tones is going to be most annoying in future especially in vehicles equipped with hybrid, electric and start/stop at idle technologies, for improved fuel economy mandates in future.
Due to increased demands for quieter vehicle interiors with higher airflow for achieving quick thermal comfort, the HVAC systems are designed with lower pressure drop which helps reduced low frequency broad-band noise but does not mask the BPF tone and its harmonics. There are persistent challenges to give best or max performance at low airflow noise and with suitable sound quality. This investigation presents several potential counter-measures that were evaluated to develop the most cost-effective design-fix to suppress the perception of blade passing tone at the subsystem and validated at the vehicle level for various major modes of HVAC system operation without affecting the air-flow and A/C system performance.