The basic principle of the RAYNOISE system
The RAYNOISE system can also be considered as a sound quality aural system (for "audible", see reference [1]). It is mainly based on geometric acoustics. Geometric Acoustics assumes that acoustic waves propagate around the sound in an acoustic environment. When the sound rays collide with a medium or interface (such as a wall), the energy is lost. Therefore, the energy accumulation of sound waves at different positions in the sound field is different. If an acoustic environment is treated as a linear system, the acoustic response of any location in the acoustic environment can be obtained from the characteristics of the sound source simply by knowing the impulse response of the system. Therefore, the acquisition of impulse response is the key to the overall system. In the past, the simulation method was mostly used, that is, the scale model was used to obtain the impulse response. Since the late 1980s, with the rapid development of computer technology, digital technology is gradually taking the lead. The core of digital technology is to use a multimedia computer to model and program the impulse response. The technology is simple, fast, and the accuracy can be continuously improved, which is unmatched by analog technology. There are two well-known methods for calculating impulse response: the Mirror Image Source Method (MISM) and the Ray Tracing Method (RTM). Both methods have their own advantages and disadvantages [1]. Later, some methods were combined to combine them, such as Conical Beam Mehtod (CBM) and Triangular Beam Method (TBM) [1]. RAYNOISE uses these two methods in combination as the core technology for calculating the acoustic response of the sound field [2].
Application of RAYNOISE system
RAYNOISE can be widely used in industrial noise prediction and control, environmental acoustics, architectural acoustics and the design of analog reality systems, but the original intention of the designer is room acoustics, which is mainly used for computer simulation of hall sound quality. To carry out the hall sound quality design, it is first required to accurately and quickly establish a three-dimensional model of the hall, because it is directly related to the precision of computer simulation. The RAYNOISE system provides a friendly interface for computer modeling. The user can directly input the three-dimensional model generated by AutoCAD or HYPERMESH, or the user can select the model in the system model library and complete the definition of the model. The main steps of modeling include:
(1) start RAYNOISE; (2) select the model; (3) input geometric size; (4) define the material and properties of each surface (including sound absorption coefficient, etc.); (5) define the sound source characteristics; (6) define the receiving Field; (7) Other descriptions or definitions, such as the number of sound rays to be considered, the number of reflection stages, and so on.
The user can use the mouse to view the defined model and the characteristics of different internal structures (differentiated by color) from different angles on the screen. Then you can start the calculation. By processing the calculation results, acoustic parameters such as sound pressure level, A sound level, echo map, and frequency impulse response function of a point in the receiving field of interest can be obtained. If you want to know the listening effect of this point, you can first convert the impulse response into a binaural transfer function and convolute it with the dry signal recorded in the anechoic chamber beforehand, you can hear the point through the ear. Listening effect.
Characteristics and deficiencies of RAYNOISE
Compared with several other sound field simulation softwares that have appeared in the past 10 years, such as Signalgic's Hypersignal-Acoustic 3.4 and EASE 2.0, RAYNOISE is more mature in terms of use and function, and it has formed A relatively complete, independent aural system. Hypersignal-Acoustic 3.4 can only be used as a hardware and software interface for other audible software [3], that is, it can only perform the convolution operation of the dry signal with the impulse response from other software and simulate the listening effect. EASE 2.0 also needs to be used in conjunction with EARS (Electronically Auralization Room Simulation) to achieve auralization. However, although the RAYNOISE Revision 3.0 system has been greatly improved on the basis of the previous version, there is a breakthrough in both the use and the calculation accuracy. However, since it is always based on geometric acoustics, it is inevitable. Will be limited by geometrical acoustics. For example, its simulation effect in low-frequency or small-scale space is relatively poor, which will inevitably greatly reduce its application range. For another example, it can only give simulation results of a simple sound source (such as a point source) at a given point, but it does not work well for a moving sound source, a distributed sound source, a directional sound source, and a more complicated situation.
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