Audio Filter CHOP
The Audio Filter CHOP removes low frequencies, high frequencies, both low and high, or removes a mid-frequency range.
A Low pass filter removes the higher frequencies of a sound, while a high pass filter reduces the bass of the sound. A band pass filter is used to extract a frequency range (i.e. extracting a person's voice from background noise) and a band reject filter is used to cut out a frequency range.
If a certain frequency lies outside the pass band, sounds at that frequency will be reduced in magnitude. The farther outside the pass band the frequency is, the more it will be reduced.
The Cutoff frequency is also known as the "half-power" frequency. A wave at the cutoff frequency will be reduced to half power.
The Rolloff of a filter determines how quickly the drop occurs at its Cutoff frequencies. A low rolloff will produce a gradual filter falloff (more of the sounds outside the frequency range are heard), and a high rolloff will produce a sharp filter falloff.
Refer to audio filter for more insight.
You can see the effects of the Audio Filter CHOP by passing it white noise from an Oscillator CHOP and sending the result to an Audio Spectrum CHOP. The Audio Filter CHOP is implemented with a 4-pole filter internally.
Moving the Dry / Wet parameter to Dry will bring back the incoming signal un-affected.
Input 2: See Cutoff Modulation Channels
Parameters - Filter Page
/filter - The filter type:
- Low Pass - All frequencies below the High Cutoff are passed through the filter (the "pass band").
- High Pass - All frequencies above the Low Cutoff are passed through.
- Band Pass - All frequencies between the Low and High Cutoff are passed through.
- Band Reject - All frequencies above the High Cutoff and below the Low Cutoff are passed though.
/units - The filter cutoff frequency can be expressed in Hz (menu set to Frequency) or power-of-10 (menu set to Logarithmic). It enables one of the next 2 Filter Cutoff parameters.
Filter Cutoff (Hz = 10**val)
/cutofflog - The filter cutoff frequency expressed in power-of-10, where value 0 translates to 1 Hz (10**0), value 1 is 10 Hz (10**1), value 2 is 100 Hz (10**2), value 3 is 1000 Hz, value 4 is 10,000 Hz, value 4.5 is 31,623 Hz. The parameter in this form gives more meaningful range in relation to human hearing, as increasing the parameter by 1 raises the frequency by about 3 octaves.
Filter Cutoff (Hz)
/cutofffrequency - The filter cutoff frequency expressed in Hz (cycles per second). This parameter set to 1000 has exactly the same effect as the above parameter set to 3.
/resonance - Increasing the resonance will boost the loudness of the passed frequencies near the cutoff frequency.
Roll-Off (dB per Octave)
/rolloff - Rolloff determines how much the levels decrease near the cutoff frequency. This parameter will make it decrease by 12 decibels (dB) per octave, to, more extremely, 24 decibels per octave. 12 and 24 decibels correspond to levels of about 1/4 and 1/16.
Dry / Wet Mix
/drywet - As this parameter is reduced from 1 (Wet) toward 0 (Dry), it removes the effect of the filter.
Parameters - Common Page
Scope - The filter effect can be limited to only some of the channels by placing their channel names here, e.g.
The python member
.chanIndex can be used to apply a different parameter value for each channel.
Cutoff Modulation Channels Input
The second input is the Cutoff Modulation Channels, which allows the filter parameters to be changed within the CHOP's time slice interval (typically 1/60 sec). This prevents audible stepping of the parameters that you are changing quickly.
You can send in a channel called
cutofffrequency to override the value of the parameter. You would do this if you want to adjust the cutoff frequency very quickly. The parameter can only change as fast as the timeline rate, typically 1/60 seconds. Changed quickly, the stepping in frequency is noticable. To improve on that, you would send a
cutofffrequency channel in that is at a higher sample rate, like 400, which you can set in a CHOP like an LFO CHOP.