Performing Calibration

Performing calibration regularly ensures quality measurements and traceability. Use the .exe files, in the C:\Program Files\National Instruments\Audio and Acoustics\Calibrations directory, to calibrate the speaker test and microphone test.

If you use a version earlier than Audio and Acoustics Test Software 23.3, use the calibration VIs, in the C:\Program Files (x86)\National Instruments\LabVIEW version\ProjectTemplates\Source\Audio and Acoustics\Library\Calibration directory, instead of the .exe files.

Note NI recommends that you apply the same configuration to calibration and test.

Calibrating Amplifiers

The Calibrate Amplifier.exe measures the frequency response of the amplifier under test with a swept sine technique. Test results for magnitude and phase are saved to the test data results file. The test result for phase will be used to exclude amplifier phase impact from the speaker test result.

Complete the following steps to calibrate an amplifier:
  1. Wire the amplifier output and input to the AI and AO ports of the sound and vibration module, respectively.
  2. Open the Calibrate Amplifier.exe.
  3. Configure the AO and AI channel names according to the instrument names in NI Measurement & Automation Explorer (NI MAX).
  4. Specify the folder to save the calibration result file.
  5. Optional: Specify settings, such as frequency range and amplitude.
  6. Click Play to run the .exe file.
  7. Navigate to the calibration result file to view calibration results.

Calibrating Delays

The Calibrate Delay.exe generates an analog output noise signal and measures the delay, in samples, between the generated signal and the acquired signal. The value of delay samples can be used to remove the delay part in subsequent measurement tests.

Complete the following steps to calibrate delays:
  1. Open the Calibrate Delay.exe.
  2. Configure the AO and AI channel names according to the instrument names in NI MAX.
  3. Optional: Specify additional settings on the front panel.
  4. Click Play to run the .exe file.
You can find calibration results in the average propagation delay indicator or the Calibration Delays.csv file in the C:\Users\Public\Documents\National Instruments\Audio and Acoustics\Configuration Files directory.

Calibrating Microphones

Use a microphone calibrator and the Calibrate Microphone.exe to perform an end-to-end calibration on the selected channel. The microphone calibrator and the Calibrate Microphone.exe measure the actual sensitivity of the sensor connected to the channel and return the measured sensor sensitivity. The reference microphone sensor sensitivity is needed for subsequent measurements.

Complete the following steps to calibrate a microphone:
  1. Connect the microphone to the sound and vibration module.
  2. Open the Calibrate Microphone.exe.
  3. Configure the AI channel name according to the instrument name in NI MAX.
  4. Place the microphone in the microphone calibrator, as the following figure shows.

    1378

    • a. Microphone
    • b. Calibrator
    The calibrator typically generates a 94 dB or 114 dB tone at a specified frequency, such as 1 kHz.
  5. Configure the calibration level and calibration frequency according to the microphone calibrator environment.
  6. Click Play to run the .exe file.
You can find calibration results in the calibrated microphone sensitivity indicator or the Microphone Sensitivity.csv file in the C:\Users\Public\Documents\National Instruments\Audio and Acoustics\Configuration Files directory.

Calibrating Mouth

The Mouth Equalization Chirp.exe and the Mouth Equalization Stepped Frequency.exe adjust the stimulus signal and equalize the mouth to flat the target sound pressure level (SPL). After running, the .exe files generate a correction curve, which can be applied to the stimulus signal when performing a test without a reference microphone.

Complete the following steps to calibrate a mouth:
  1. Open the Mouth Equalization Chirp.exe or the Mouth Equalization Stepped Frequency.exe according to the signal type.
  2. Configure the AO and AI channel names according to the instrument names in NI MAX.
  3. Specify the parameters of the stimulus signal to be tested.
    Tip You can obtain the signal amplitude for the sound pressure you want to test by running the Get Output Level from Sound Pressure(Pa).exe.
  4. Specify sample rate and trigger settings.
    Tip You can obtain the propagation delay by running the Calibrate Delay.exe.
  5. Specify the folder to save the calibration result file.
  6. Click Play to run the .exe file.
  7. Select whether to calibrate again in the Is the frequency response curve flat enough? window.
A correction curve is saved to the calibration result file. When you perform a test with the same stimulus signal without a reference microphone, you can apply the correction curve.

Calibrating Microphone Sensitivity

The following .exe files can test the sensitivity of a microphone with or without a calibrated mouth:

  • Analog Microphone Sensitivity with Calibrated Mouth.exe
  • Analog Microphone Sensitivity.exe
  • Digital I2S Microphone Sensitivity with Calibrated Mouth.exe
  • Digital I2S Microphone Sensitivity.exe
  • Digital PDM Microphone Sensitivity with Calibrated Mouth.exe
  • Digital PDM Microphone Sensitivity.exe
Complete the following steps to calibrate the sensitivity of a microphone:
  1. Open an .exe file in the preceding list according to your test needs.
  2. Configure the hardware resource, such as AO and AI settings.
  3. Configure the single tone stimulus signal.
    Tip If you do not use a reference microphone, you can obtain the signal amplitude for the sound pressure you want to test by running the Get Output Level from Sound Pressure(Pa).exe.
  4. Specify sample rate and trigger settings.
  5. Optional: Specify sound pressure if you do not use a reference microphone.
  6. Optional: Specify propagation delay if enable sync pulse in single tone is disabled.
    Tip You can obtain the propagation delay by running the Calibrate Delay.exe.
  7. Click Play to run the .exe file.
You can find calibration results in the sensitivity indicator or the Microphone Sensitivity.csv file in the C:\Users\Public\Documents\National Instruments\Audio and Acoustics\Configuration Files directory.

Calibrating AO Output Voltage

The Get Output Level from Sound Pressure(Pa).exe gets the output voltage of an analog output signal for a given sound pressure.

Complete the following steps to calibrate the AO output voltage:
  1. Open the Get Output Level from Sound Pressure(Pa).exe.
  2. Configure the AO and AI settings.
  3. Configure the single tone settings.
  4. Specify init volt, sound pressure, tolerance, sample rate, and trigger settings.
  5. Optional: Specify propagation delay if enable sync pulse in single tone is disabled.
    Tip You can obtain the propagation delay by running the Calibrate Delay.exe.
  6. Click Play to run the .exe file.
If the generated sound pressure is within the tolerance, the Get Output Level from Sound Pressure(Pa).exe stops and returns the AO voltage for the specified sound pressure. You can find calibrated voltage also in the Output Voltages.csv file under the C:\Users\Public\Documents\National Instruments\Audio and Acoustics\Configuration Files directory.