Flutter Echo Modeling

Gloria Dal Santo, Karolina Prawda and Vesa Välimäki

Companion page for a paper submitted to the 25th International Conference on Digital Audio Effects (DAFx 2022)

Abstract

Flutter echo is a well-known acoustic phenomenon that occurs when sound waves bounce between two parallel reflective surfaces, creating a repetitive sound. In this work, we introduce a method to recreate flutter echo as an audio effect. The proposed algorithm is based on a feedback structure utilizing velvet noise that aims to synthesize the fluttery components of a reference room impulse response presenting flutter echo. Among these, the repetition time defines the length of the delay line in a feedback filter. The specific spectral properties of the flutter are obtained with a bandpass attenuation filter and a ripple filter, which enhances the harmonic behavior of the sound. Additional temporal shaping of a velvet-noise filter, which processes the output of the feedback loop, is performed based on the properties of the reference flutter. The comparison between synthetic and measured flutter echo impulse responses shows good agreement in terms of both the repetition time and reverberation time values.

Examples of flutter echo synthesized with our method

RIR 1 - Variable acoustc laboratory Arni

	Reference	Synthesized
RIR
	Dry	Reference RIR	Synthesized RIR
Drums
Speech
Singing

RIR 2 - Electrical room

	Reference	Synthesized
RIR
	Dry	Reference RIR	Synthesized RIR
Drums
Speech
Singing

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