Noise Control Measures Based on Acoustic Principles
Sound absorption
The noise in the limited space of a car includes two parts: direct sound level meter and reflected noise. Sound absorption is the use of special passive materials to change the direction of sound waves in order to absorb their energy. Reasonable arrangement of sound-absorbing materials can effectively reduce the reflection of sound energy and achieve the goal of sound absorption and noise reduction. Due to limitations in environmental protection, waterproofing, fireproofing, and lightweight, commonly used sound-absorbing materials for automobiles are relatively rare. Calm soundproof sound-absorbing cotton is a creatively developed special-shaped sound-absorbing groove design by R&D personnel based on the research and analysis of the noise characteristics of multiple car models. It integrates more than twice the sound-absorbing area of a traditional unit of soundproofing area, and the width, depth, slope, and curvature of each sound-absorbing groove are determined through mathematical algorithm simulation according to the characteristics of car noise. Due to the gradual transition nature of the sound-absorbing layer, the acoustic impedance of the material can be well matched with that of air, enabling efficient absorption of sound waves in a wide frequency range.
shock absorption
The outer shell of a car is usually made of thin metal plates. During the driving process, the earthquake source transmits its vibration to the body of the car, which propagates in the form of elastic waves. When these thin plates are excited by vibration, they produce noise and also cause vibration in other components of the car. These components radiate noise outward. Installing elastic materials or components on this propagation path to isolate or attenuate the propagation of vibration can achieve the purpose of shock absorption and noise reduction. The available shock absorption measures mainly include seismic isolation and damping shock absorption. The damping protective adhesive for calm cars is developed based on the principle of damping shock absorption. In addition, the calm sound-absorbing cotton is glued manually during the bonding process. The specialized adhesive has good elasticity and flexibility after curing, forming a damping and shock-absorbing layer that can withstand the impact and vibration of the vehicle body.
seal up
A large number of experiments have shown that the control of overall noise inside the car is closely related to the sealing performance of the vehicle body. A good seal can effectively reduce the overall noise of the vehicle, especially effectively suppressing wind noise during high-speed driving. The turbulence generated during vehicle operation is the root cause of wind noise - periodic airflow separation occurs at a certain part of the vehicle body during high-speed driving, causing vortices to drag out from both sides of the vehicle and move in the direction of the airflow, resulting in noise. The way to prevent this kind of noise is to try to avoid the separation of airflow and disrupt the periodic wake with appropriate methods. General sealing only uses the improvement of sealing performance to block out noise, while calm professional sealing strips not only block noise, but also avoid airflow separation and disrupt periodic wake, fundamentally reducing wind noise.
