Detecting overblown flute fingerings from the residual noise spectrum

Producing a tone by increasing the blowing pressure to excite a higher frequency impedance minimum, or overblowing, is widely used in standard flute technique. In this paper, the effect of overblowing a fingering is explored with spectral analysis, and a fingering detector is designed based on acoustical knowledge and pattern classification techniques. The detector performs signal analysis of the strong broadband signal, that is, spectrally shaped by the pipe impedance, and measures the spectral energy during the attack around multiples of the fundamental frequency sub-multiples over the first octave and a half. It is trained and evaluated on sounds recorded with four expert performers. They played six series of tones from overblown and regular fingerings, with frequencies that are octave- and non-octave-related to the playing frequency. The best of the four proposed sound descriptors allows for a detection error below 1.3% for notes with two and three fingerings (⁠$C5$⁠, $D5$⁠, $C6$⁠, and $C♯6$⁠) and below 14% for four $(E6)$ or five fingerings $(G6)$⁠. The error is shown to dramatically increase when two fingerings’ impedance become too similar (⁠$E6$ and $A4$ and $G6$ and $C5$⁠).