Parametrically Tunable Audio Shelving And Equalizing Ladder Wave Digital Filters
Salina Abdul Samad · 2003
Parametrically tunable audio equalizers are conventionally realized using allpass digital lter networks. They consist of rst-order shelving lters and second-order equalizing lters. In this paper, ladder wave digital lters (WDFs) with parametrically tunable coecients are proposed as shelving and equalizing lters. Similar to the allpass realization, the transfer function power complementary property of WDFs is used to obtain ecient shelving and equalizing lters. However, unlike the allpass structures, the transfer function and the tunable parameters of the ladder WDF are derived from the analog lter equivalent of the digital shelving and equalizing lters. For the shelving WDF, the cut-o frequency and gain are tunable, while for the equalizing WDF, the tunable parameters are the center frequency, 3-dB bandwidth and gain. The transfer functions are derived and shown in terms of the tunable coecients for both the shelving and equalizing WDFs. Key Words: Tunable parameters, audio shelving lters, equalizing lters, wave digital lters. 1.