Reconstruction of binaural room impulse responses using spherical harmonics

Dynamic virtual acoustic environments based on modelled signals can be constructed from online or offline calculations of the binaural room impulse responses. For the former, calculations have to be very fast for a real-time dynamic experience, while for the latter the storage requirements may become huge. An approach to reconstruct binaural room impulse responses based on offline calculated impulse responses is proposed here. It relies on a dual-radius open sphere with receiver points around the listener' position, allowing to post-process the signals to any desired head-rotation within the sphere using spherical harmonics. An inverse calculation is done as well, from the centre of the receiver sphere to a dual-radius sphere around the source position. Based on these calculations, a plane wave decomposition is applied in the post-processing algorithm to compute the time-dependent angle(s) of incidence at the receiver and angle(s) of departure at the source, such that the impulse responses at the receiver dual-radius sphere can be reconstructed for a translated source position. As a result, based on two room acoustic calculations, the post-processing algorithm allows for head-rotations and source translations in the virtual environment. Prospects and limitations of this approach will be discussed.