Design and Aural Analysis of Signal Processing Using Time Delay

Abstract

This paper presents the design in PureData of some audio signals processes in real time like delay, echo, reverb, chorus, flanger e phaser. It also applies techniques of Aural Analysis, which intends to solve problems of intrinsic sound perception. We analyze the technical characteristics of each process and the psychoacoustic effects produced by them in human perception and audio applications. The approach for these processes is based mostly on Roads (1996), Berardino and Puckette (2006). We look for a better understanding of how some sound processes based on delay lines, such as simple delay, reverb and echo, affect the frequency spectrum of the processed sound during the time flow. Besides that, we identified other processes that also affect the spectrum, such as chorus, flanger e phaser, which nevertheless many times are not classified as resulting from time processes but as general effects. A deeper comprehension of the consequences of sound processes based on delay lines favors not only the awareness for the identification of the involved phenomena but also the technical choice of which process to use. This knowledge also helps the decision-making in professional audio applications such as the choice and positioning of microphones for audio recording in different acoustic spaces. This skill also benefits sound edition and mixing, besides music composition that employs sound effects in pre-processed or real time.