Abstract
Directional room impulse responses (DRIR) measured with spherical microphone arrays (SMA) enable the reproduction of room reverberation effects on three-dimensional surround-sound systems (e.g., Higher-Order Ambisonics) through multichannel convolution. However, such measurements inevitably contain a nondecaying noise floor that may produce an audible “infinite reverberation effect” upon convolution. If the late reverberation tail can be considered a diffuse field before reaching the noise floor, the latter may be removed and replaced with an extension of the exponentially-decaying tail synthesized as a zero-mean Gaussian noise. This has previously been shown to preserve the diffuse-field properties of the late reverberation tail when performed in the spherical harmonic domain (SHD). In this paper, we show that in the case of highly anisotropic yet incoherent late fields, the spatial symmetry of the spherical harmonics is not conducive to preserving the energy distribution of the reverberation tail. To remedy this, we propose denoising in an optimized spatial domain obtained by plane-wave decomposition (PWD), and demonstrate that this method equally preserves the incoherence of the late reverberation field.
Highlights
Room impulse response (RIR) convolution has become a widespread method for reproducing room reverberation effects in digital audio processing applications
We present two sets of results obtained using the proposed denoising procedure: first, by applying it to a simulated reverberation tail with temporally increasing anisotropy; and to a directional room impulse responses (DRIR) measured at the Dominicans of Haute-Alsace cultural center using an mh acoustics
This paper has addressed the problem of removing the nondecaying noise floor from DRIRs measured with an spherical microphone arrays (SMA) and presented spatially anisotropic yet incoherent late reverberation tails
Summary
Room impulse response (RIR) convolution has become a widespread method for reproducing room reverberation effects in digital audio processing applications. The late reverberation field of a DRIR may become spatially incoherent without being energetically isotropic [10]; in other words, the stochastic process describing the plane waves incident on the SMA will have a certain spatial power distribution (or an amplitude density distribution, strictly speaking) This may be due to the particular geometric and/or absorptive characteristics of the measured space (e.g., coupled volumes, semi-open spaces, highly heterogeneous absorptive surfaces, etc.), in combination with the directivity and orientation of the sound source (which in general may not be perfectly omnidirectional), and can be investigated using directional energy decay curves (DEDC) [11] or energy decay deviations (EDD) [12] calculated on a spatial representation of the DRIR. As we show below, such anisotropic spatial distributions of the late reverberation tail cannot be arbitrarily recreated through analysis and synthesis in the SHD, and a different spatial representation must be used for denoising
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