ENGINE SOUND POWER CALCULATIONS AND CONTRIBUTION OF EACH SURFACE TO DRIVER EAR: SOUND PARTICLE VELOCITY APPROACH

摘要

Vehicle in-cabin ambience quality depends on many parameters such as aesthetics and ergonomics. Ergonomics related to cabin acoustics is discussed here. Quieter the car's engine more pleasant the cabin ambience will be. Vibration is the cause and sound is the effect as per cause/effect analogy. Engine's surface vibration causes the sound to radiate in the cabin. At an early stage of a program, knowing engine's sound radiation behavior proves beneficial in optimizing the source (engine) and saving sound package materials. In this document, a method for calculating engine's airborne sound power has been elaborated. A new concept for computing engine sound power using radiation impedance and surface velocity is devised. The computed sound power along with Power Based Noise Reduction (PBNR) transfer function is used to predict the cabin Sound Pressure Level (SPL). Accordingly, future target levels can be set for source (L_w), transfer path (PBNR) and receiver (L_p) respectively. Engine's response in different driving conditions is also studied in detail and it is concluded that for airborne noise reduction at frequencies >200 Hz, working at low idle is enough and it will be reflected in other driving conditions automatically.