The Influence of Overlapping Band Filters on Octave Band Decay Curves

Stockwell transform for estimating decay time at low frequencies

“…The algorithm was compared with the one-third octave method to clearly show the limitations of the standard methods, which are often misused as such. The decay function of the observed frequency band calculated with the traditional one-third octave method was shown to be influenced by slowly decaying neighbouring modes, which is consistent with the results presented in the literature [18,31]. In addition, the decay at the observed frequency band was shown to be altered by a standard filtering process even when the neighbouring mode decays rapidly, especially when having higher amplitude.…”

“…For the presented signal h 1 , the optimal value of γ opt is 1, which is used to calculate decay times. As a result, the standard method yields incorrect values in the neighbouring frequency bands, which is consistent with the results obtained by Marbjerg et al [31] for higher frequency bands.…”

“…Xiang [20], Marbjerg et al [31] and Seoane et al [18]. In this experiment, the For each value of γ, the concentration measure was calculated using Eq.…”

“…The second source of error is leakage of energy from adjacent frequency bands which has been discussed in recent articles. The study by Marbjerg et al [31] showed that the overlap of the bandpass filters used in practise can influence the decay functions of the 4 kHz and 8 kHz octave bands. Using a simulation tool based on geometrical acoustics, the authors found that the reverberation times obtained directly from octave band energy impulse responses are lower than the values obtained by filtering the full bandwidth impulse response with class 1 filters.…”