Parametric filters are superior to ordinary equalizers – which comprise a bank of filters - because they provide independent adjustment of the centre frequency, gain and bandwidth of the individual filters within the filter bank. Normal equalizers are restricted to the adjustment of gain alone. As such, parametric filters are widely deployed in audio and musical applications.
Signal Wizard allows parametric filters be designed and executed in real time with ease, either using an FIR or IIR approach. Signal Wizard also goes beyond normal parametric design, and uses a super parametric approach – even the phase of each filter can be precisely defined.
As an example, the upper frequency response shows a filter (FIR approach) with a two peaks the first at 3.5 kHz with a gain of 0.8, and the second at 16.5 kHz with a gain of 0.6. The Signal Wizard Filter Design Interface shows the input parameters. In the lower trace, a third peak has been added at 10 kHz with a gain of 1.0. Note that neither the bandwidths nor the gains of the original two peaks have altered.
Arbitrary filter execution is one of the most powerful features of Signal Wizard. An arbitrary filter is specified by importing a text file which represents the chosen frequency or impulse response. Either real or complex frequency filters may be designed, allowing complete phase control.
In the example on the left, an arbitrary filter has been designed by importing a section of an audio file which contains a single word (top trace). This is now the impulse response. The lower trace shows its spectrum, i.e. the frequency response. This arbitrary filter can be downloaded to the hardware at the click of a button. If we now play the audio file through Signal Wizard, it will select and enhance every occurrence of that word.
Arbitrary filters have a host of applications including vibration control, noise cancellation, musical instrument enhancement, loudspeaker correction, biomedical signal processing and many more.