Fluctuation Strength Computation

Fluctuation strength (like roughness) is a sensation induced by signal fluctuations.

In Sound: Analysis and Specification, Fluctuation Strength is based on the thesis work of Sontacchi, A. Entwicklung eines Modulkonzeptes für die psychoakustische Geräuschanalyse unter MATLAB. Master thesis, Technischen Universität Graz, 1998, pp 1-112. This implementation was inspired by the Roughness model of Daniel and Weber, and is therefore quite similar in its main structure. A few important differences must nonetheless be noted:

• Fluctuation Strength is computed over the whole signal, while Roughness is calculated frame by frame

• The filtering performed to isolate the modulation components (here centered at 4 Hz instead of 70 Hz for Roughness) is performed differently (through decimation of the input signal, while also accounting for temporal masking), and the filter shape does not change over the Bark scale.

• The aggregation of specific Fluctuation Strength values uses a quadratic sum rather than a direct sum.