A robust denoising process for spatial room impulse responses with diffuse reverberation tails

Spatial room impulse responses (SRIRs) measured using spherical microphone arrays are seeing increasingly widespread use in reproducing room reverberation effects on three-dimensional surround sound systems (e.g., higher-order ambisonics) through multi-channel SRIR convolution. However, such measured impulse responses inevitably present a non-negligible noise floor, which may lead to a perceptible "infinite reverberation effect" when convolved with an input sound. Furthermore, individual sensor noise and momentary measurement artefacts may additionally corrupt the resulting impulse response. This paper presents a robust SRIR denoising procedure applicable to impulse responses with diffuse late reverberation tails, which can be modeled by a stochastic process. In such cases, the non-decaying frequency-dependent noise floor may be replaced by a synthesized incoherent tail parameterized by the SRIR's energy decay envelope. It is shown that performing such tail re-synthesis in the spherical harmonic domain, using an independent zero-mean Gaussian noise for each component, preserves both the reverberation tail's frequency-dependent decay as well as its spatial coherence properties. The proposed process is then evaluated through its application to SRIRs measured in real-world conditions, and finally some aspects of performance and consistency verification are discussed.