y range, audiologists need to choose wisely which type of processing to use. Minimally, signal processing for noise reduction is analogous to a continually adjusting graphic equalizer for a home stereo system. Level dependent frequency response (LDFR) hearing aids can also adjust their "equalizer" settings based on input volume. Along with standard fitting techniques, subjective client opinions are one of the most important factors in decreasing hearing aid returns. In the past several years, technological advances have given audiologists several options.
             One such LDFR hearing aid incorporates BILL (bass increase at low levels) circuitry. If it were assumed that most detrimental noise occurs in the low frequencies, then decreasing the low frequency response of a hearing aid at high levels would reduce noise and improve a person's speech discrimination performance score. This concept seems natural based on the upward spread of masking principle. Since a low frequency sound must travel farther up the basilar membrane, it will
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