Third-octave band filter leakage flattens the lower slope of measured loudness patterns

Evidence

Generally used third-octave band filters show a leakage towards neighbouring filters of about -20 dB. This means that a 70 dB, I-kHz tone produces the following levels at different centre frequencies: 10 dB at 500 Hz, 30 dB at 630 Hz, 50 dB at 800 Hz and 70 dB at 1 kHz. Therefore, in agreement with the model of loudness, the lower slope of the loudness pattern becomes less steep. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1320

Categorization

• QUESTION: How does filter leakage at -20 dB compare across different filter bank designs (FFT vs analog)? Worth checking whether newer loudness meters account for this.