How Smooth Can You Go, Can You Go Down Low?: an analysis on the frequency-dependent roughness of velvet-noise

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master_Roberts_Jade_2023.pdf (1.74 MB)

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Sähkötekniikan korkeakoulu | Master's thesis
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Date

2023-12-11

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Major/Subject

Acoustics and Audio Technology

Mcode

ELEC3030

Degree programme

CCIS - Master’s Programme in Computer, Communication and Information Sciences (TS2013)

Language

en

Pages

43+6

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Abstract

Temporal roughness has been studied in earlier works on broadband velvet noise but, the frequency-dependency of temporal roughness has little previous research. Velvet noise is a sparse pseudo-random signal that has been applied to late reverberation modeling, decorrelation, speech generation and extending signals. This thesis explores combinative qualities such as pulse density, filter type and filter shape as well as a way to perceptually test their contribution to frequency-dependent temporal roughness. An adaptive perceptual test was conducted to find the lowest densities where velvet noise was still perceived as smooth at octave bands and corresponding lowpass bands. The results showed that the cutoff frequency of a lowpass filter as well as the center frequency of an octave filter is correlated with the perceived lowest density of smooth velvet noise. When the lowpass filter with the lowest cutoff frequency, 125 Hz, was applied, the filtered velvet noise sounded smooth at a median of 668 pulses/second and a median of 290 pulses/second for octave filtered noise at a center frequency of 125 Hz. For the broadband velvet noise, the minimal density of smoothness was found to be at a median of 1587 pulses/second. The results of this thesis are applicable in designing velvet-noise-based artificial reverberation with minimal pulse density.

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Supervisor

Välimäki, Vesa

Thesis advisor

Fagerström, Jon

Keywords

velvet noise, frequency-dependency, sparse noise, artificial reverberation modeling, temporal smoothness

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https://urn.fi/URN:NBN:fi:aalto-202312187470

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[dipl] Sähkötekniikan korkeakoulu / ELEC