Loads a set of calibration data to compensate for the soundcard's frequency
response. The calibration file is a plain text file which by default has the extension .cal, though
other extensions are also accepted.
It should contain the actual gain (and optionally phase) response of the soundcard
at the frequencies given, these will then be subtracted from subsequent measurements.
The values in the calibration file can be separated by spaces, tabs or commas.
- Each line of calibration data must have a frequency value and a
gain value, a phase value is optional
- Frequency is in Hz, gain in dB, phase in degrees
- The cal points can be at arbitrary frequency spacing, but each
line must have a higher frequency than the one before and there
must be at least 2 freq, gain data pairs
- Only lines which begin with a number are loaded, others
are ignored
- In comma-delimited files there must be at least one space after the comma
- Spaces before values are ignored
- The sample rate at which the data was generated can be indicated by having
a line which starts "Sample Rate:" followed by the sample rate in Hz. The Wizard
checks for this when loading a file and will warn if the rate does not match the
current soundcard setting - calibration data generated at a different sample rate
will not provide accurate correction.
Here is an example of a valid file format:
Soundcard Calibration data saved by Room EQ Wizard V3.26
Source: SoundMAX Digital Audio, Wave Out Mix, Right channel, volume: 0.075
Format: 48000Hz sampling, Log Swept Sine, 176ms pre-impulse, 1,000ms post-impulse
Dated: 28-Nov-2005 17:19:51
Sample Rate: 48000
0 -9.38
1 -7.69
2 -6.34
3 -5.22
4 -4.26
5 -3.48
6 -2.80
7 -2.20
8 -1.71
9 -1.28
10 -0.87
11 -0.55
12 -0.25
After a calibration file has been loaded it wil be applied to all subsequent
measurements. Loading the calibration file does NOT affect any data already
measured and does not affect any measurement data that is imported. The
graph display is updated to show the calibration curve, offset to lie at the centre
of the graph window.
Linear interpolation is used between calibration points. Outside the range of the
calibration data the behaviour depends on whether C weighting compensation has
been selected. If C weighting compensation is selected, C weighting curve figures
will be used for frequencies above or below the range of frequencies in the
calibration data. If not, the calibration values for the lowest frequency in the file
will also be applied for all lower frequencies and the calibration values for the
highest frequency in the file will be applied for all higher frequencies.
The calibration file name and path are remembered for the next startup, the
file will be loaded automatically when the Wizard is opened. A message confirming
loading of the file is given.
To stop calibration data being applied, use the "Clear calibration data" option.
Useful tip: To apply or remove a soundcard calibration file
to a measurement after it has been taken, simply load or clear the cal data
as required and press the Apply Windows button in the
Impulse Response Controls
graph group to recalculate the frequency response.