Modeling of HVAC Noise in a Simplified Car Model 2018-01-1522

To assure high comfort for vehicle passengers, the interior noise has to be designed to be low in volume as well as in a pleasant way. Vehicle’s HVAC (heating, ventilation and air-conditioning) noise becomes increasingly audible when the main sound sources are acoustically optimized. Thus, the Sound Quality of HVAC noise needs to be evaluated early in the development process. For assessing the Sound Quality of HVAC noise, suitable evaluation criteria as well as the knowledge of the acoustics of the new HVAC system are required. Suitable evaluation criteria were identified using listening tests. In a second step HVAC noise was investigated in different environments: HVAC as a component, HVAC as a system (including air ducts and vents) and HVAC system integrated in a simplified car model. The model was designed acoustically similar to a series vehicle. Thus, the size as well as the interior paneling of a series vehicle was approximated by using sound-absorbing and -reflecting material. The suitability of the car model was proofed by analyzing the HVAC sound fields of two different HVAC systems of different vehicle classes and comparing those to the sound fields measured in the corresponding series vehicles. Furthermore, the influence of geometrical properties of the interior, such as the interior length, the inclination angle of the windscreen, the shape of the vehicle’s rear end and the consideration of seats, was investigated. All parameters mainly influence the modal field by affecting the natural frequencies. In the other frequency domains, the interior length, the inclination angle of the windscreen, and the shape of the rear end were of secondary importance. Seats are an important parameter in sound field modeling, due to their sound absorbing and reflecting effect. Using a car model as a test bench for modeling HVAC noise early in the product development process enables an early assessment of the Sound Quality of HVAC noise.