Filter widening preserves Rayleigh envelope statistics while electrode-current summation does not.

Evidence

Because the smearing is due to wider filters, rather than envelope summation, the resultant envelopes from broader filters still have Rayleigh-distributed envelopes with the same overall relative modulation power as the envelopes from narrower filters (i.e., the same area under the modulation power spectrum, normalized to DC; see Fig. 1 ). In contrast, with CIs, the envelopes derived from summing the envelope currents from adjacent electrodes are no longer Rayleigh distributed and have lower modulation power, relative to the overall (DC) power in the envelope (Hu and Beaulieu 2005 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 2164

Categorization

• DEFINE: Clarifies the technical distinction between broadening filters (preserves Rayleigh distribution) versus summing electrode currents (breaks Rayleigh statistics) — the core mechanism separating HI from CI envelope degradation.