Two-Stage Attenuation Filter for Artificial Reverberation

Vesa Välimäki, Karolina Prawda, and Sebastian J. Schlecht

Companion page for a paper submitted to the IEEE Signal Processing Letters

Cite as: Vesa Välimäki, Karolina Prawda, and Sebastian J. Schlecht, "Two-Stage Attenuation Filter for Artificial Reverberation", Submitted to IEEE Signal Processing Letters, doi:

Code available here.

Abstract

Delay networks are a common parametric method to synthesize the late part of the room reverberation. A delay network typically consists of several feedback loops, each containing a delay line and an attenuation filter, which approximates the same decay rate by appropriately setting the frequencydependent loop gain. A challenge in such delay network reverberators is the design of the attenuation filters based on a measured room impulse response. Until now, it has been difficult to control the decay rate accurately on the whole audio band. This letter proposes a novel two-stage attenuation filter structure, which simplifies and sharpens the design. The first stage is a low-order pre-filter approximating the overall shape and determining the decay at the two ends of the frequency range, the dc and the Nyquist limit. The second filter, an equalizer, fine-tunes the gain at different frequencies, such as on one-third-octave bands. A design example using the proposed method in the design of an interleaved velvet-noise reverberator is exhibited. A method to estimate the target attenuation filter response is also described. It is shown that the proposed design is more accurate and robust than previous methods. The proposed two-stage attenuation filter is a step toward a realistic parametric simulation of measured room impulse responses.

Examples of RIRs synthesized with different filter designs

All sound examples were resampled with fs = 16 kHz.

Reference - RIR of Pori hall

RIR synthesized with only GEQ

RIR synthesized with median gain as a pre-filter and a GEQ

RIR synthesized with median gain, notch filter, and a GEQ

RIR synthesized with the proposed method

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