Lemur: A bandwidth-enhanced sinusoidal modeling system
Kelly Fitz, Lippold Haken · The Journal of the Acoustical Society of America · 1998
Lemur models sounds as a collection of partials having amplitude, bandwidth, and frequency envelopes. Bandwidth envelopes allow the neat representation of noisy parts of sounds which produce clutter in purely sinusoidal analyses. Lemur associates noise energy with sinusoidal components that are nearby in frequency. Bandwidth envelopes record the fraction of the partial energy that is attributable to noise energy, as opposed to sinusoidal energy. Amplitude envelopes are calculated to include the energy added by the bandwidth association process. When partials are pruned from the model, in the analysis process or during editing, Lemur preserves the overall energy by distributing the removed partials energy among neighboring partials. For sounds with a good spread (in frequency) of partials, Lemur can represent noise energy in the appropriate spectral regions while retaining the manipulability and homogeneity of a purely sinusoidal model. This homogeneity is important for implementing certain kinds of model-domain behaviors and real-time timbral manipulation. Lemurs synthesis includes a spectral line widening technique to spread energy away from each partial’s center frequency according to bandwidth envelope values.