Late-Reverberation Synthesis Using Interleaved Velvet-Noise Sequences

2021 24th International Conference on Digital Audio Effects (DAFx)

2021

A perceptual study revealing a novel connection between modal properties of feedback delay networks (FDNs) and colorless reverberation is presented. The coloration of the reverberation tail is quantified by the modal excitation distribution derived from the modal decomposition of the FDN. A homogeneously decaying allpass FDN is designed to be colorless such that the corresponding narrow modal excitation distribution leads to a high perceived modal density. Synthetic modal excitation distributions are generated to match modal excitations of FDNs. Three listening tests were conducted to demonstrate the correlation between the modal excitation distribution and the perceived degree of coloration. A fourth test shows a significant reduction of coloration by the colorless FDN compared to other FDN designs. The novel connection of modal excitation, allpass FDNs, and perceived coloration presents a beneficial design criterion for colorless artificial reverberation.

Section: Perceptual Evaluation Of Modal Excitation Distributionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Role of Modal Excitation in Colorless Reverberation

Heldmann

2021 24th International Conference on Digital Audio Effects (DAFx)

2021

“…The presented experiments use exponentially decaying Gaussian noise (GN), selected to mimic the late response of an actual SRIR, and also decaying velvet noise (VN). Velvet noise is a ternary, sparse sequence with special properties that has been used to create computationally inexpensive single-channel reverberators (Holm-Rasmussen et al, 2013;J€ arvel€ ainen and Karjalainen, 2007;V€ alimaki and Prawda, 2021) and decorrelators (Alary et al, 2017;Schlecht et al, 2018). Until now, no spatial reverberators using velvet noise have been created, and we hope that our results can aid in such a design as well.…”

Section: Introductionmentioning

confidence: 99%

“…Throughout the study, we will use the term "roughness" to describe the perceptual quality of non-smooth sparse noise. The main reason is that it has been used in earlier studies regarding the perception of sparse noise by J€ arvel€ ainen and Karjalainen (2007), V€ alimaki et al (2013), and V€ alimaki and Prawda (2021. In psychoacoustics, roughness is linked to amplitude modulation (Fastl and Zwicker, 2007).…”

Section: Introductionmentioning

confidence: 99%

Perceptual roughness of spatially assigned sparse noise for rendering reverberation

Meyer-Kahlen

The Journal of the Acoustical Society of America

Lokki

2021

Multichannel auralizations based on spatial room impulse responses often employ sample-wise assignment of an omnidirectional response to form loudspeaker responses. This leads to sparse impulse responses in each reproduction loudspeaker and the auralization of transient signals can sound rough. Based on this observation, we conducted a listening test to examine the general phenomenon of roughness due to spatial assignment. First, participants assessed the roughness of both Gaussian noise and velvet noise, assigned sample-wise to up to 36 loudspeakers by two algorithms. The first algorithm assigns channels merely by selecting random indices, while the second one constrains the time between two peaks on each channel. The results show that roughness already occurs when few channels are used and that the assignment algorithm influences it. In a second experiment, virtualizations of the test were used to examine the factors contributing to increased roughness. We systematically show the effect of spatial assignment on noise and conclude that besides time-differences, level-differences caused by head-shadowing are the principal cause for the perceived roughness. The results have significance in spatial room impulse response rendering and spatial reverberator design. V

“…Convolution of any other signal with VN can be implemented efficiently, when the sparsity of VN is accounted for [1,3]. Several signal processing applications based on VN have evolved, such as artificial reverberation [1,[3][4][5], audio decorrelation [6,7], speech synthesis [8,9], and acoustic measurements [10].…”

mentioning

confidence: 99%

Colours of velvet noise

Meyer-Kahlen

Välimäki

2022

Electronics Letters

Velvet noise is a sparse ternary pseudo-random signal containing only a small portion of non-zero values. In this work, the derivation of the spectral properties of velvet noise is presented. In particular, it is shown that the original velvet noise is white, i.e. has a constant power spectrum. For velvet noise variants with altered probability of polarity, the spectral characteristics are analytically derived. Crushed additive velvet noise is shown to have potential in the design of coloured sparse noise sequences, which are useful in acoustic signal processing.