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Brick Wall Filter
These filters differ from their “Hi-Fi” counterparts in that they are very steep digital filters used to attenuate signals that are interfering with a poor quality audio signal. These are FIR (Finite Impulse Response) filters that exhibit a very high degree of out of band attenuation. Also, they exhibit a phase-linear response with respect to frequency (all frequencies are delayed by the same constant amount of time). These FIR based filters are predominantly used for forensics audio applications.
The Brick Wall Filter
The Brick Wall Filters include the following choices of filter shapes:
Several controls are provided:
You can monitor the signal being removed by the brick wall filter by previewing its reciprocal filter. In other words, if you are using the Bandpass filter, switch the system to the Bandstop filter to hear what is being removed. Similarly, if you are using the Lowpass filter at a certain frequency, switch to the Highpass filter at the same frequency to hear what is being removed. The same logic applies to the Highpass filter; just use the Lowpass filter set for the same frequency to hear what is being removed.
*Note - Only applies to the Bandpass and the Bandstop filters.
These filters differ from their “Hi-Fi” counterparts in that they are very steep digital filters used to attenuate signals that are interfering with a poor quality audio signal. These are FIR (Finite Impulse Response) filters that exhibit a very high degree of out of band attenuation. Also, they exhibit a phase-linear response with respect to frequency (all frequencies are delayed by the same constant amount of time). These FIR based filters are predominantly used for forensics audio applications.
The Brick Wall Filter
The Brick Wall Filters include the following choices of filter shapes:
- Lowpass: Only allows signals below the corner frequency to be fed to its output.
- Highpass: Only allows signals above its corner frequency to be passed to its output.
- Bandpass: Allows only the signals between its chosen lower frequency and its upper frequency setting to be passed to its output.
- Bandstop: Rejects all signals between its selected “Frequency” and “Upper Frequency” limits.
Several controls are provided:
- Frequency - (Hertz) (Range is from 3 Hz to 20,000 Hz)
- Length - (Samples up to 4,094) - The larger the value of this parameter, the greater the degree of rejection past the filters corner frequency setting. However, the higher the setting for length, the larger will be the computational demands on your computer. So, large values of "length" will take longer to process or may cause your machine "stutter" in preview or live real time modes.
- Upper Frequency Control - Sets the upper limit for the filter's bandwidth when operating in either Bandpass or Bandstop mode. (Range is from 3 Hz to 20,000 Hz)*
- Frequency Control (Lower) - Sets the lower limit for the filter's bandwidth when operating in either Bandpass or Bandstop mode. (Range is from 3 Hz to 20,000 Hz)*
You can monitor the signal being removed by the brick wall filter by previewing its reciprocal filter. In other words, if you are using the Bandpass filter, switch the system to the Bandstop filter to hear what is being removed. Similarly, if you are using the Lowpass filter at a certain frequency, switch to the Highpass filter at the same frequency to hear what is being removed. The same logic applies to the Highpass filter; just use the Lowpass filter set for the same frequency to hear what is being removed.
*Note - Only applies to the Bandpass and the Bandstop filters.