Loads a set of calibration data for a calibrated microphone or SPL Meter,
or calibration values you would like to be applied to your measurements. 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 microphone
or SPL meter being used 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. ETF5 calibration files are in a suitable format.
- 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
Here is an example of a valid file format:
Microphone calibration data
516.797 0.000 0.000
538.330 -0.012 0.078
559.863 -0.024 0.163
581.397 -0.035 0.251
602.930 -0.045 0.339
624.463 -0.055 0.426
645.996 -0.065 0.512
667.529 -0.076 0.598
689.063 -0.087 0.688
710.596 -0.098 0.782
732.129 -0.109 0.882
753.662 -0.119 0.985
775.195 -0.129 1.092
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 mic/meter 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.