DUG Insight User ManualDUG Insight DUG Insight User Manual ProcessesTrue-Amplitude Frequency Equalisation (TAFE)

True-Amplitude Frequency Equalisation (TAFE)

Description Control boost with user-defined frequency/gain pairs.
Module(s) Image Gather Processes
Requirements Volume
Related
Works with Gathers


True Amplitude Only Frequency Equalisation (TAFE) performs true amplitude manipulation of the amplitude spectrum via 3 possible methods:

  1. Frequency/ Gain pairs
  2. Rho filter compensation
  3. Simple exponential boost

Note: these processes are all zero-phase processes i.e. only amplitude spectrum is changed.

  1. In the Control Panel, open the Process tab.
  2. At the tab header, click the Add icon and select New Process.
  3. Scroll down and double-click on True-Amplitude Frequency Equalisation (TAFE).
  4. Type a name for the process and click OK.

Frequency/Gain pairs

The amount of boost is controlled by user-defined frequency/gain pairs.

Gain values between control points are linearly interpolated. The first and last control point are constant extrapolated as required to cover the range of frequencies in the data.

For example, this set of pairs:

Frequency (Hz)    30    60
Gain (dB)         0     60

will perform no boost below 30 Hz; linearly increase the boost from 0 to 6 dB between 30 and 60 Hz; and boost a constant 6 dB above 60 Hz.

  1. Volume: Select the input volume.
  2. Mode: Click and select Pairs boost
  3. Apply inverse: Optionally reverse the application.
  4. Use decibels: Parameterise using decibels rather than scalars.
  5. Points: Frequency/gain pairs
  6. Post filtering: Apply an optional band pass, high pass or low pass filter after application.                        
  7. Rescale trace Envelope: Post-application gain normalisation. This is achieved by applying the ratio of the envelopes of the input and output to the output.            This function can be smoothed in time.                        

RHO filter compensation

This filter is based on the rho filter which is commonly applied in processes that involve stacking of many traces e.g. migration, srme and slant stacking. Stacking or integration has a 1/frequency filter response. This filter is linear in frequency but may be used to modify the spectrum non linearly in frequency by specifying an exponent other then 1 e.g. a value greater than 1 will boost higher frequencies more.

  1. Volume: Select the input volume.
  2. Mode: Click and select Rho.
  3. Apply inverse: Optionally reverse the application.
  4. Unchanged frequency: Frequency about which the filter will pivot.
  5. Rho exponent: Controls the degree of filtering.
  6. Taper start /end (Hz): Optionally taper the effect of the filter on the low frequencies.
  7. Low frequence ramp end: Optionally control the starting frequency of filtering.
  8. Post filtering: Apply an optional band pass, high pass or low pass filter after application.
  9. Rescale trace Envelope: Post-application gain normalisation. This is achieved by applying the ratio of the envelopes of the input and output to the output. This function can be smoothed in time.

Exponential Boost

A simple boost function is applied relative to a user defined reference frequency.

  1. Volume: Select the input volume.
  2. Mode: Click and select Exponential boost.
  3. Apply inverse: Optionally reverse the application.
  4. Reference frequency: Frequency hingepoint. Frequencies above and below this frequency will be gained with different functions.
  5. Exponent for high frequencies: Frequencies greater than the reference frequency will be boosted by the gain function exp [ A*(RefFrequency-f) ] where A is this parameter.
  6. Exponent for low frequencies: Frequencies lower than the reference frequency will be boosted by the gain function exp [ B*(f-RefFrequency) ], where B is this parameter.
  7. Post filtering: Apply an optional band pass, high pass or low pass filter after application.
  8. Rescale trace Envelope: Post-application gain normalisation. This is achieved by applying the ratio of the envelopes of the input and output to the output. This function can be smoothed in time.

Note: All options have the following additional parameters that can be specify

  1. Apply a frequency filter after application.
  2. Apply gain compensation to the output data such that the output has the same energy after application as before application. This is achieved by applying the ratio of the envelopes of the input and output to the output. This function can be smoothed in time.
  3. Inverse of filter can be applied.