A new automatic IIR analysis/synthesis technique for plucked string instruments

In this paper, an automatic way of analyzing/synthesizing plucked-string instruments by using a simple IIR (infinite impulse response) structure is presented. The basic structure of the proposed IIR filter consists of a delay line with feedback loops pulled out from the delay line back to the input side of the filter. The feedback portion acts like a prediction filter to modify the signal for the next period such that it can be as close to the original tone as possible. The delay line and the prediction filter provide the mechanism to produce the desired pitch of the synthetic sound. The design of the coefficients for this IIR synthesizer is accomplished by using a neural network based training algorithm. The excitation signal is extracted from the original tones recorded from the target instrument. Several sets of filter coefficients are required for different synthesis stages such as attacking part and sustain part. The proposed algorithm is tested over a wide range of plucked-string instruments. Although it requires more computation compared to some model-based approaches, the analysis work is simple and straightforward. In addition, the synthetic tone sounds very close to the correspondent original sound.