Estimation of reed flow signal from instrument performance.
Tamara Smyth, Jonathan S. Abel · The Journal of the Acoustical Society of America · 2010
In this work we present a technique for estimating the reed flow signal, typically a periodic sequence of pulses, from the recorded sound of a reed instrument. The instrument is modeled as a reed coupled to a 1-D waveguide having unknown filter elements that must first be determined before constructing the instrument reed flow transfer function. As pressure waves make two round trips from the mouthpiece to the bell and back for each reed pulse, the output periodic pressure has two distinct halves: the second half being roughly the first half filtered by the instrument’s propagation losses. Estimation of these losses is not simply a spectral ratio, as the two halves are not temporally disjoint and the beginning of the reed pulse period is often unclear. The running autocorrelation of the recorded signal is zero phase and naturally provides the beginning of the period of the recorded signal as well as clear first and second phases that may be analyzed to estimate the round-trip losses in the instrument. Combining these losses with the direct measurements of the bell reflection function, a filter is developed which inverts the implied waveguide to produce the reed flow estimate.