The low-cut or bass-cut filter is used to reduce amplification of low frequencies. This filter is used if the hearing impaired person has normal or near normal hearing in the low frequencies, or experiences trouble hearing in noisy environments.
There are various degrees of filter slopes, ranging from a slope of 6 dB per octave in a traditional, first order passive filter, to 12, 18 or 24 dB per octave in an active filter (which contains an amplifier). Special tone filters may have a variable slope.
The number of filtering components (such as capacitors) determines the order of the filter. A first order filter can be designed using only one capacitor, while four are needed in a 4th order filter.
Fig. 3.19 Low cut ...