# Noise Analysis and Structural Optimization of Automobile Scroll Compressor Air Valve
## 1 Introduction  
The primary function of the automobile air conditioning system is to regulate the indoor temperature to optimize a comfortable and efficient driving experience. The air conditioning compressor, as a vital component of this system, plays a pivotal role in this process. Compressor noise commonly observed during operation includes pneumatic noise, vibration noise, and electromagnetic noise [1]. When the air conditioner is activated, the valve switch is closed to ensure uniform discharge of compressed gas. However, when the gas is discharged at high speed and pressure, it impinges on the static wall structure, inducing airflow regeneration noise, a phenomenon commonly referred to as pneumatic noise [2]. Aerodynamic noise, on the other hand, is generated by uneven internal fluid flow velocity or pulsation of fluid surface pressure, which significantly impairs driving and riding comfort. Noise, Vibration, and Harshness (NVH) has emerged as a key indicator of in-vehicle comfort, with increasing emphasis placed on this aspect by private car owners and car manufacturers in recent years [3]. Therefore, the management and control of compressor aerodynamic noise has become a key focus of this study. At present, most air conditioning noise management strategies focus on the design and modification of compressor structure. In their studies, [PERSON] et al. successfully reduced vibration noise and aerodynamic noise in the 50-1600 Hz frequency range through modifications to this component [4]. Similarly, [PERSON] et al. reduced the operating noise of a twin screw compressor by establishing end face attenuation channels and increasing Helmholtz resonators in the exhaust pipe. Simulation and experimental results show that the mean noise reduction values achieved are in the range of 5.0 dBA-10.0 dBA [5]. Someresearchers have also focused on modifying or enhancing the muffler structure to reduce noise levels. For example, [PERSON] et al. identified the noise source as exhaust noise and improved the original exhaust channel structure by using three parallel muffler chambers to connect to the air conditioning pipeline, resulting in a 9.5 kPa reduction in airflow pulsation and a nearly 6 dBA reduction in sound pressure level [6]. [PERSON] et al. identified the noise source based on near-field noise measurements and reduced the sound pressure level by 4.1 dBA by proposing a noise control method coupled with structural optimization and perforated mufflers [7]. [PERSON] et al. improved the structure of the air conditioning compressor anechoic enclosure through a combination of experiment and simulation, thus achieving the effect of reducing the sound pressure level [8]. [PERSON] et al. analyzed the noise spectrum and found that mid- and high-frequency attenuation needs to be improved. They modified the original air filtration muffler structure by increasing the flow regulator box and replacing the internal filler material with aluminum silicate rock wool. In addition, a resistive muffler mechanism was connected in parallel with the original structure to mitigate wideband noise. These two integrated air filtration mufflers reduced sound pressure levels by 23.6 dBA and 24.6 dBA, solving the above problems [9]. [PERSON] et al. innovated on the traditional, poorly sealed muffler by designing a muffler that could be partially snapped together at the top and bottom. This new muffler design, including an upper and lower cover snapped together, significantly reduced the chamber leak problem. The innovative muffler structure not only reduced the sound pressure level by 1.87 dBA but also increased the cooling capacity by 7.4 W [10]. [PERSON] et al. proposed an innovative system that uses an amphibian waveguide and two quarter wavelength tubes (QWTs) with different cross-sectional sizes. When sound waves enter the narrow tube, they are effectively absorbed by the spacing between the tubes, achieving noise absorption of 5.2 dBA in a frequency range of 6400 Hz.