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Standard calibration files for common speakers and microphones are provided with BioSigRZ and a speaker-specific custom calibration file might also have been provided with your speaker. If a calibration file is not provided for your specific speaker model or the distance (free-field experiments) or length of tube (closed-field experiments) is different, you can create a custom file using BioSigRZ's Calibration tools. You will need a calibration microphone with a flat response in the band of interest.

The extension for calibration files is .tcf. All TCF files should be stored at: C:\TDT\BioSigRZ\TCF

During calibration, BioSigRZ performs a sweep over the frequency range of interest and generates a speaker response curve along with a correction curve that would be required to flatten the response. An FIR filter is calculated from the correction curve and stored in the contents of the TCF file. When you load the TCF file, that filter is loaded onto the RZ6 so that any sound stimulus you present through the RZ6 is calibrated to a flat response across all frequencies.

How often you calibrate is up to you. Some prefer to calibrate every day, others prefer once a week, month or longer. BioSigRZ offers two tools to verify your .tcf file to see if it needs to be replaced or if the file is working as needed.

Creating a Custom Calibration (.tcf) File

BioSigRZ's calibration generation tools are only available when using a Calibration configuration file (.acf).

To open the calibration configuration file:

  1. Click the File menu and click Open Config. File

  2. In the Open dialog box, select the C:\TDT\BioSigRZ\Configs\Calibration\CAL200k.acf file then click Open.

To create a custom calibration file:

  1. Select Calibration from the Setup menu or click the Calibration button. The Calibration Profile window is displayed.

  2. Click the Microphone Calibration Browse (...).

    TDT provides a set of microphone TCF files in your BioSigRZ installation. You will need to know the sensitivity (in mV per Pascal) of the microphone to pair it with the correct file. The generic microphone calibration files are named according to their sensitivity (such as 1.0mV.tcf).

    In addition, TDT provides calibrations files for two ACO microphones. The files for these microphones are named according the microphone part number: ACO_7016.tcf (which is assumed to be 3 mV/Pa) and ACO_7017.tcf (assumed to be 1.1 mV/Pa). By choosing the sensitivity closest to your microphone’s actual sensitivity you guarantee accuracy of no worse than 1 dB. Note: if your microphone sensitivity is far outside of this range of the provided microphone TCF files, contact TDT.

    Select the file that is closest to your microphone sensitivity and click Open.

  3. In the Probe group box:

    1. The default Level (vrms) value of 1.000 should be suitable in most cases. If you need to change the value, enter the desired voltage. However, note that the standard SIG files are programmed with a 1 Vrms stimulus and must be changed if this value is modified.

    2. Enter a Low Freq (Hz) and High Freq (Hz) that includes the frequency range used in your experiment. The calibration curve has some smoothing applied so the range must be wider than the experimental paradigm requires to avoid edge effects during filter generation.

    3. The Rate (Hz/s) value determines how quickly the frequency range is swept. The default value of 3000 should be suitable in most cases. Sweeping too slowly creates a very irregular correction curve that is difficult to model accurately with an FIR filter.

  4. In the Filter Options group box:

    1. Enter your Target Level (dB). This should be set to highest level you will use in your experiment. However, note that the standard SIG files are programmed to 90 dB and must be changed if this value is modified.

    2. Do NOT change the Max Cor (dB) value without specific instructions from TDT. The default value of 20 dB (with a 1 Vrms level) limits the DAC output to 0.1-10 V. The upper limit ensures your signal does not exceed the system's 10 V DAC limit and avoids clipping. The lower limit keeps your signal to noise ratio high.

    3. Enter the appropriate Filer Length:

      1. For free field speakers, enter 1024.

      2. For closed field speakers enter 256.

  5. If using TDT electrostatic speakers (ES1, EC1), connect the speaker to the RZ6 Electrostatic A connector and ensure the Electrostatic switch is set to ON. Otherwise turn the Electrostatic switch to OFF and attach your speaker to the RZ6 Out-A connector.

  6. Attach your microphone to the RZ6 In-A connector and set the AMP/BYP switch to the AMP position.

  7. Set the Gain (DB) knob to the position indicated in your calibration microphone .tcf file. This is listed in the 'Gain:' field of the Microphone Calibration panel.

    Best Practices: If using a closed field system be sure the tubing connecting the microphone and the speaker is as straight as possible and there are no connections where air can leak out. If using an open field system, place the speaker where it will be positioned during the experiment, and place the microphone where the animal's ear will be positioned.

  8. Click the Start Sweep button.

    The blue trace shows the frequency response of the speaker and the yellow trace shows the harmonic distortion (THD). If there is less than 20 dB of separation between these traces there may be a problem with your speaker or recording setup.

    If the red Correction curve reaches the -20 dB correction limit, adjust the Atten knob on the RZ6 to lower the output level of the speaker and click 'Start Sweep' again to perform another frequency sweep.

    If the red Correction curve reaches the 20 dB maximum correction factor:

    1. Ensure your speaker and microphone are connected to the RZ6 correctly.

    2. If you are using a closed field speaker, ensure the tubing is straight and there are no leaks.

      If all connections and tubing have been checked and the curve continues to exceed the 20 dB maximum, try one or more of the following:

      1. Lower the Target Level

      2. If in closed field configuration, shorten your tubing

      3. If in free field configuration, move your microphone closer to your speaker

  9. Once you have a satisfactory calibration, click the Create Calibration File to save your calibration file.

  10. In the TCF Specs dialog, enter a File Name and any additional information about your speaker set-up. Note: Gain Setting should be set to the value of the Atten knob.

  11. Click the Make TCF button.

  12. A message is displayed to confirm the file has been created. Click OK

  13. To return to the Calibration profile window, click Done

Testing the Calibration (TCF) File

  1. To test your newly created calibration file, click the Speaker Calibration Browse (...) button

  2. In the Specify a Speaker Calibration File dialog box, select the file name you specified earlier, and click Open

  3. In the Calibration Profile window, click Start Sweep

    If the speaker is calibrated correctly the blue response curve should be flat and at your target level.

You can also test calibration files in your ABR or DPOAE configuration.

After loading your configuration:

  • Click Calibration on the Setup menu.


  • Click the Calibration button

The Calibration window shown below is opened.

The Speaker Calibration will be populated with the speaker calibration data specified in your Setup > Stimulus > Channel dialog.

The Microphone calibration file should be the file you used to make the .tcf file.

By adjusting the Freq field and then selecting "A" or "B" you can test the calibration at the specific frequencies used in your paradigm.

The Speaker Calibration will change to match the currently selected speaker (A or B).

The dB value shown should match your target level with only a slight deviation.