Figure 16. Octave band filters used to create re-synthesized broadband peaky speech (left, blue), diotic multiband peaky speech with four bands (middle, red), and dichotic multiband peaky speech using five bands with audiological center frequencies (right, red).

The last band (2nd, 5th, and 6th, respectively, black line) was used to filter the high frequencies of unaltered speech during mixing to improve the quality of voiced consonants. The designed frequency response using trapezoids (top) was converted into time-domain using IFFT, shifted, and Nuttall windowed to create impulse responses (middle), which were then used to assess the actual frequency response by converting into the frequency domain using FFT (bottom).