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High Pass Filter
A High-pass filter only passes signals that are above or "higher" than the corner frequency. It reduces the level of low frequency signals that are below the corner frequency. The effect can be similar to turning down the bass control on a home stereo. This filter is very useful for reducing turntable rumble, muddiness, and any other extraneous low frequency noise in a recording.
High Pass Filter with Chebyshev or Butterworth Response with up to 4th Order Slope
This is a digital simulation (IIR based) of a conventional analog High-pass filter having a Butterworth or Chebyshev response (for the higher order slopes). This filter attenuates frequencies below the High-pass corner frequency. Just like the Band-pass and the Low-pass filter, this filter has four slopes available. They are 6 dB / Octave, 12 dB / Octave, 18 dB / Octave and 24 dB / Octave. This filter is very useful for reducing the effects of turntable rumble, or microphone seismic effects from inducing "muddiness" onto an audio recording. It can also be used to eliminate any dc (fixed) offset that may have developed on a .wav file (a preset is provided which performs this function). To reduce turntable rumble, start with a setting of 60 Hz and 18 dB / Octave, and then adjust the parameters until you are satisfied. This filter is also useful when selectively applied for reducing microphone "P" popping effects on the vocal track of multi-track recordings wherein an adequate windscreen had not been utilized in the session. Effective settings to attenuate “P” popping typically are 120 Hz with a slope of 18 dB / Octave (selectively applied to the highlighted event).
The High Pass Filter
Note: The higher order (12, 18, & 24 dB / Octave) High-pass filters are of the Butterworth or Chebyshev types, depending upon your selection.
The following is a summary of the control parameters and range of adjustment provided for the High-pass Filter:
Note: The frequency range of adjustment up to 19,999 Hz is only effective when utilizing a 44.1 kHz sampling rate. At a 22.05 kHz sampling rate, the maximum effective frequency setting will be 10 kHz, and at an 11.025 kHz sampling rate, this value will drop to 5 kHz.
High-pass Filter Operating Procedure (Tutorial)
Note: For a steeper filter response at the expense of elevated pass-band ripple, choose the Chebyshev rather than the Butterworth response.
Removing DC-Offsets with the High-pass Filter (Tutorial)
The High-pass Filter can be used to remove any DC-Offset from .wav file. To do so, set the High-pass Filter to 10 Hz and 6 dB per octave, and run it on the .wav file needing correction. This feature can also be found as a preset within the High-pass filter.
A High-pass filter only passes signals that are above or "higher" than the corner frequency. It reduces the level of low frequency signals that are below the corner frequency. The effect can be similar to turning down the bass control on a home stereo. This filter is very useful for reducing turntable rumble, muddiness, and any other extraneous low frequency noise in a recording.
High Pass Filter with Chebyshev or Butterworth Response with up to 4th Order Slope
This is a digital simulation (IIR based) of a conventional analog High-pass filter having a Butterworth or Chebyshev response (for the higher order slopes). This filter attenuates frequencies below the High-pass corner frequency. Just like the Band-pass and the Low-pass filter, this filter has four slopes available. They are 6 dB / Octave, 12 dB / Octave, 18 dB / Octave and 24 dB / Octave. This filter is very useful for reducing the effects of turntable rumble, or microphone seismic effects from inducing "muddiness" onto an audio recording. It can also be used to eliminate any dc (fixed) offset that may have developed on a .wav file (a preset is provided which performs this function). To reduce turntable rumble, start with a setting of 60 Hz and 18 dB / Octave, and then adjust the parameters until you are satisfied. This filter is also useful when selectively applied for reducing microphone "P" popping effects on the vocal track of multi-track recordings wherein an adequate windscreen had not been utilized in the session. Effective settings to attenuate “P” popping typically are 120 Hz with a slope of 18 dB / Octave (selectively applied to the highlighted event).
The High Pass Filter
Note: The higher order (12, 18, & 24 dB / Octave) High-pass filters are of the Butterworth or Chebyshev types, depending upon your selection.
The following is a summary of the control parameters and range of adjustment provided for the High-pass Filter:
- Frequency: 5 - 19,999 Hz.
- Slope: 6, 12, 18, 24 dB / Octave
- Preview Mode Button: On / Off (The slider controls can be adjusted "live" when the preview mode button is activated.)
- Filter Type: Choice of Butterworth or Chebyshev
Note: The frequency range of adjustment up to 19,999 Hz is only effective when utilizing a 44.1 kHz sampling rate. At a 22.05 kHz sampling rate, the maximum effective frequency setting will be 10 kHz, and at an 11.025 kHz sampling rate, this value will drop to 5 kHz.
High-pass Filter Operating Procedure (Tutorial)
- Highlight the portion of your .wav file on which you desire to apply the High-pass filter. (You may choose to highlight the entire file or any portion thereof.)
- Click on the “High Pass Filter”. (Filter Menu)
- Choose the "Frequency" below which you desire to attenuate all signals, utilizing the right mouse button in conjunction with the "Frequency" slider control. When the control is all the way down, the setting will be 5 Hz, and when it is all the way up, the setting will be 20 kHz. (Useful settings will usually fall somewhere within the 15 Hz to 500 Hz range, depending on the goals of the audio restoration process.) If you desire finer frequency resolution, you may also use direct numeric entry of the value.
- Choose the Filter "Slope" which you desire. Click on either 6 dB / Octave, 12 dB / Octave, or 18 dB / Octave or 24 dB / Octave. The steeper the slope, the higher will be the degree of attenuation of all frequencies below the "Frequency" setting.
- Click on “Preview” to audition the results before processing.
- After a short delay, you will hear the effect of the settings that you have chosen. (The system may seem to stutter if your computer is too slow to keep up with the algorithm in real time. However, this repeating pattern will not be present in the final Destination processing of the filter.)
- As the filter is running in either preview mode or normal mode (Destination File Mode), you will see a dialog box that indicates the "% Done" of the filter algorithm on the selected portion of the Source .wav file. Also, at the top of the Dialog box you will see indicated the "Total Samples to Process:"
- Keep adjusting the Frequency and Slope parameters, and testing the various settings using the "Preview" mode until you are satisfied with what you hear.
- When you are satisfied, click on “Run Filter”, and the filter will process your Source .wav file through the filter algorithm, and create a Destination .wav file containing the output of the filter.
- When this process is complete, you will see the Destination File become highlighted in Yellow, at the same time that the Source File becomes unselected.
Note: For a steeper filter response at the expense of elevated pass-band ripple, choose the Chebyshev rather than the Butterworth response.
Removing DC-Offsets with the High-pass Filter (Tutorial)
The High-pass Filter can be used to remove any DC-Offset from .wav file. To do so, set the High-pass Filter to 10 Hz and 6 dB per octave, and run it on the .wav file needing correction. This feature can also be found as a preset within the High-pass filter.