Band-Pass Filter

Description Apply high-pass, low-pass or band-pass frequency filters to an input volume.
Module(s) Insight
Requirements Volume, Window model (optional)
Related Spectra Analysis, Spectral Decomposition
Works with 2D, Stacks, Gathers, Depth volumes

The Band-pass Filter performs high-, low-, or band-pass filtering on a volume based on a frequency range. The process uses a zero-phase Butterworth filter that passes a range of frequencies and rejects frequencies outside the range.

Filters are defined using pass and stop frequencies, corresponding to the 95% and 5% amplitude points on the filter (see images below).

A time/depth-varying windowing model can be specified to apply different filters to different time windows.

Performance warning: Band-pass filtering is a computationally-intensive process that requires processing entire traces. The resulting output volume may be slow to use. Consider:

Create a band-pass filter

Create band-pass filter process
  1. In the Control Panel, open the Process tab.
  2. At the tab header, click the blue "+" icon and select New Process.
  3. Double-click or search for Band-pass Filter.
  4. Type a name for the process and click OK.

Define band-pass filter settings

  1. In the Details Panel, select the input volume. In this example, a gather volume is selected.
  2. Select the Use a minimum phase filter checkbox to apply a minimum phase filter.
  3. You can also choose to Output noise model instead of filtered traces check box.
  4. Select the Filter type:
    • High pass
    • Band pass
    • Low pass

Filtering Settings

  1. Select a Windowing Model
    • Select <<Whole Trace>> to apply one set of filter parameters to the whole trace.
    • Select a Windowing Model to apply different parameters to each window. See Creating a Windowing Model for more details on window models.
    • If a Windowing Model is used, pass and stop frequencies must be provided for each window.
  2. As a result of this process, a new volume is available in the Volume tab.

Filter type: Band pass

The band pass filter passes frequencies in a range between specified low and high values.

Define band-pass filter settings
  • Specify filters via Pass and Stop
    • If unchecked, define the filter with a 3dB down frequency and the slope in dB per octave
    • If checked, define the filter ramp between two values, a stop (5%) and a pass (95%) frequency
  • Specify the low cut-off and high cut-off frequency values as needed.

Filter type: High Pass

The high pass filter passes frequencies above a specified value.

  • Specify filters via Pass and Stop
    • If unchecked, define the filter with a 3dB down frequency and the slope in dB per octave
    • If checked, define the filter ramp between two values, a stop (5%) and a pass (95%) frequency
  • Specify the cut-off frequency values as needed.

Filter type: Low Pass

The low pass filter passes frequencies below a specified value.

  • Specify filters via Pass and Stop
    • If unchecked, define the filter with a 3dB down frequency and the slope in dB per octave
    • If checked, define the filter ramp between two values, a stop (5%) and a pass (95%) frequency
  • Specify the cut-off frequency values as needed.

The following example show a gather volume before and after the low-pass filter is applied.