Download Improving Spectral Analysis Precision with an Enhanced Phase Vocoder using Signal Derivatives The purpose of this presentation is to demonstrate the practical interest of an original improvement of the classic Fourier analysis. The n-th order short-time Fourier Transform (FTn) extends the classic short-time Fourier transform by also considering the first n signal derivatives. This technique greatly improves Fourier analysis precision not only in frequency and amplitude but also in time, thus minimizing the well-known problem of the trade-off of time versus frequency. The implementation of this analysis method leads to an enhanced phase vocoder particularly wellsuited for extracting spectral parameters from the sounds.
Download A Hilbert-Transformer Frequency Shifter for Audio In contrast to conventional pitch-shifting effects which attempt to maintain harmonic relationships in the signal, a frequency shifter translates all the component frequencies of the input signal by an equal amount, disrupting the harmonic relationships and radically altering the sonic qualities of the signal. Ring modulation is a generalization of double-sideband suppressed-carrier modulation, and the frequency shifter is equivalent to a single-sideband modulator. Applications of the frequency shifter include the creation of bizarre distortions, phaser, and rotating speaker effects. An implementation is presented that is suitable for fixed-point digital hardware.
Download Musical Gestures and Audio Effects Processing We introduce the notion of musical gestures as time varying measurements which identify the audio input stream’s musical skeleton without attempting to implement any involved model of musical understanding. Living comfortably at an intermediate level of abstraction between wave forms and music transcriptions, these musical gestures are used to control the behavior of an audio processing module. The resulting scheme qualifies as an audio effects processing system as it essentially transforms an audio stream into another.