Abstract
It is useful to compute sound field of a source in a virtual environment which is different from the measurement environment. For example, some properties of sound source, such as directivity index and frequency response curve, are required to be measured in an anechoic room or free space, but both of them cannot be always accessible. Consequently, it will be useful to compute sound field of a source in free space when sound field of the source is not measured in the free space. In the aforementioned example, the free space is a virtual environment. Based on reciprocity theorem and modal expansion, a method to predict sound field of a source in a virtual environment is given in this paper when the scattering effect of the source can be neglected. Reciprocity theorem builds the relationship between measured sound field and predicted sound field, which plays an important role in the method. Green’s function in the virtual environment is needed in the method. To restrict measurement points on an enclosed surface, the Green’s function is expanded by a set of modes. A simulation is given to examine the validity of the method.
Highlights
Virtual acoustic reconstruction (VAR) which mainly focuses on computer-aided simulation of building acoustics is a well-established tool for the study of the acoustic behavior of such spaces and is often combined with virtual acoustic representation to provide direct aural impression of their response to speech or music signals [1-4]
When the virtual environment is equal to the real environment, sound field reconstruction methods, such as near-field acoustical holography (NAH) [5-16], inverse boundary element method (IBEM) [17-19], and least-squares method (LSM) [20, 21], can be used to compute sound field stimulated by a certain source and the properties of the source do not need to be known in advance
When a virtual environment is different from the real environment, sound field reconstruction is not a suitable method to compute sound field stimulated by a certain source in a virtual environment
Summary
Virtual acoustic reconstruction (VAR) which mainly focuses on computer-aided simulation of building acoustics is a well-established tool for the study of the acoustic behavior of such spaces and is often combined with virtual acoustic representation (auralisation) to provide direct aural impression of their response to speech or music signals [1-4]. To compute sound field stimulated by a source in a virtual environment by VAR, the properties of the source, such as directivity and frequency response, must be known. A method called extended virtual acoustic reconstruction (EVAR) is proposed which maps sound field in an arbitrary real environment to that in a virtual environment without knowing properties of the excitation source in advance when scattering effect of the source can be neglected. One cannot reconstruct SFV with the Green's function directly based on reciprocity theorem when SFR is not accessible in the whole domain This problem can be overcome by expanding the Green's function with a set of modes which satisfy homogeneous Helmholtz equation, and the measurement points are restricted on an enclosed surface which contains the sound source.
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