Study On The Test System And Research Of Complex Elastic Modulus Of Paper Diaphragm For Loudspeaker

The material's properties of paper diaphragm, such as elastic modulus, Poisson ratio, damping factor, thickness, density etc. has great impact on speaker performance. So the material for paper-making can be chosen by its mechanical property. This can guarantee the good sound quality of loudspeaker.At present, it is common to get the material properties by static test. However, dynamic elastic modulus is more useful than static elastic modulus in practice because it can reflect the vibration characteristic better. Paper material is not absolute elastic. There are few test methods and instruments for elastic module. Some methods are difficult to operate. It is necessary to develop a practical and accurate test method for dynamic elastic module, which can help companies to design, manufacture of loudspeaker's paper diaphragm, choose the cone paper, and develop new types of paper diaphragm materials.A system for complex elastic modulus measurement of loudspeaker paper diaphragm material based on acoustical excitation is designed in this paper. Vibration signal of paper is detected by a laser transducer in a non-contact way. Meanwhile sine sweeping excitation method is used for testing. A set of vibration apparatus, detection and analysis software are developed. The dynamical model of cantilever considering the viscoelasticity of paper material has been built, making the results of dynamic elastic modulus and damping factor more accurate.The system is composed of three parts. In the first part, cone paper sample is stimulated by sound pressure in different frequencies, and makes resonance at corresponding frequency. In the second part, the system collects the voltage signals of vibration, and then converts them into digital data, so the computer can deal with them. In the third part, the software shows, records data, and then uses these data to plot amplitude-frequency curve by cubic fitting. At last, the complex elastic modulus including damping factor and dynamic elastic modulus are computed by the software.Experiments illustrate that the system has high accuracy, repeatability and dependability, and it can satisfy the need.