This brief communication exposes an overview of various wavenumber filters to separate the rail contribution to pass-by noise via the wave signature extraction method [Zea, Manzari, Squicciarini, Feng, Thompson, and Lopez Arteaga, J. Sound Vib. 409, 24-42 (2017)]. It has been found that the originally proposed filters underestimate the rail noise at frequencies above 1.6 kHz due to the presence of higher-order wave families that is unaccounted for. The goal of this letter is thus to propose and examine different filter functions that can capture such waves, and to assess whether the rail contribution estimations can be improved.