The presence of noises in the vehicle cabin is an annoyance phenomenon which is significantly affected by the heating, ventilation, and air conditioning (HVAC) system. There are very limited studies reported on the specific type of noise characterisation and validation for both model and vehicle system levels. The present study developed a model of HVAC system that reflects the operation as in real vehicle, and the investigation of the HVAC components were carried out individually to determine which component contributes to the humming-type noise and vibration. The study was conducted under two conditions; idle speed of engine (850 rpm) and operating condition (850-1400 rpm). A ixed blower speed and fullface setting were applied throughout the experimental process. Three different sensors were used for the experiment, which are: accelerometer, tachometer, and microphone. From the results, the compressor and AC pipe components have contributed the most in generating the noise and vibration for both the model and vehicle systems. The findings also highlight that the humming-type noise and vibration were produced in the same operating frequency of 300-400 Hz and 100-300 Hz for idle and operating conditions, respectively, and this result was validated for both model and vehicle system levels.

Heating, ventilation and air conditional (HVAC) system provides a cold ventilation for the comfort of the driver and passengers in a vehicle. However, the vibration induced by the HVAC contributes to a reasonable level of noise emission, and hissing is one of the critical noises. So far, the characterization of hissing noise from the vehicle is least to be reported compared to other type of noises. Hence, this paper investigates the occurrence of hissing noise from several HVAC components. A lab-scale HVAC system was developed to imitate the real-time operations of the vehicle HVAC system. Two engine conditions, namely as ambient and operating conditions, were tested at speed of 850 rpm and 850-1400 rpm, with the blower speed maintained constantly at one level. The result shows that the hissing noise from the labscale HVAC was produced at frequency range of 4000-6000 Hz. The finding also highlights that the main component contributors of noise emission are an evaporator and a thermal expansion valve. The validation with a real vehicle system showed a good consensus whereby the hissing noise was produced at the similar operating frequency ranges. Also, the hissing noise was found to be louder when in an operating condition which could be taken into consideration by the vehicle manufacturers to improve the HVAC design.