The Optimization Of Stepped Sound Diffuser’ S Shape And Arrangement Based On Sound Diffusion

Sound diffusers were widely used to provide more diffusion,lateral reflection and cancel echo etc.The diffusion properties of Schroeder diffuser have been known to people since invented.The major defect of its limited diffusion band and less diffusion when repeated over many periods led to a desire for better diffusers.A method to promote periodic diffusers’ diffusion was used when periodic stepped diffuser’s shape was directly optimized in this paper,as stepped diffuser’s simple manufacture and better diffusion.Meanwhile,the aperiodic modulation had some flaws,a new complementary aperiodic modulation was also proposed.Firstly,as theory’s limitation and characteristics of numerical simulation in frequency domain,Finite Difference Time Domain method was used to calculate diffuser’s reflected sound in time domain,the validation of Finite Difference Time Domain method was verified through comparing its calculation with experiment,theory and Boundary Element Method respectively.Then,the shape of stepped sound diffuser was optimized using hybrid method combined Finite Difference Time Domain with Immune Genetic Algorithm under normal incidence.Two optimization ways were used in the study.One was local optimization,which carried out optimization for a single stepped diffuser;the other was global optimization,which optimized periodic diffusers directly.The results were compared with Schroeder diffusers’.The results show single diffuser with better diffusion performance can be obtained in the local optimization way,but the diffuser will not remain the better diffusion performance after repeated over many periods.On the contrary,a better diffusion performance for periodic diffusers can be obtained in the global optimization way.The diffusion performance would be improved by just increasing diffuser’s order from six to twelve under the same diffusers’ overall width condition when large periodic diffusers are used in the global optimizaiton.The periodic diffusers’ good diffusion properties could also be kept under oblique incidence.The aperiodic modulation changed periodic arrangement of diffusers using modulation,but it could only improve diffusion properties at Schroeder diffuser’s design frequency.A new complementary aperiodic modulation was also proposed to make up the Schroeder diffuser’smodulation deficiency,in which two single 6-order-stepped diffusers with complementary diffusion band were designed using hybrid method mentioned above.The new aperiodic modulation could broaden diffusion band than original aperiodic modulation.At last,the global optimization’s result was compared with aperiodic modulation’s,it turns out that a stepped diffuser with higher order is needed to be used in the global optimization than aperiodic modulation when the equivalent diffusion performance to be achieved as aperiodic modulation.In this paper,a global optimization way to promote periodic diffusers’ diffusion properties was used,and a new complementary aperiodic modulation method was also proposed,both of which provide guideline for diffusers’ arrangement in large area.