Measure Acoustic Microphone Sensitivity - SM5 - SMM-A1 - SMM-A2

Song Meter SM5 User Guide
Core Product
SM5
Accessory

You can test external acoustic microphones and stub microphones using a third-party microphone calibration signal generator.

About this task

To accurately measure microphone sensitivity, you need a signal generator or microphone calibrator that produces a 1 kHz sine tone at 1 Pa sound pressure, or 94 dB SPL. The signal generator should be designed to fit microphones with a diameter of 0.5 in. An example of this type of signal generator is the Extech 407744.

Using a signal generator, you can test the sensitivity of the SMM-A1 and SMM-A2 external microphones and SM5-compatible acoustic stub microphones.

Procedure

  1. If you are testing an SMM-A1 or SMM-A2, connect it to one of the SM5's external microphone ports.
  2. Map the microphone you want to test to either ultrasonic channel using the built-in interface or the app.
    To measure the left acoustic stub microphone, you must keep the enclosure closed to avoid blocking the calibrator. Therefore, you must use the mobile app.
    • On the SM5, go to Settings > Channel.
    • Pair the app with the SM5 and select Configure > Channel.
    To test the left stub microphone, select Acoustic Ch1 > Left stub mic.
  3. Go to Utilities > Calibration mode.

    Calibration mode temporarily disables the high-pass filter, disables the preamplifier, and sets the acoustic gain setting to 0 dB. This means that changing settings for a given deployment will not affect your measurement.

    The calibration mode displays the measured signal level at 1 kHz for the two acoustic channels.

  4. Remove the microphone's foam windscreen.
    If you cannot remove the windscreen by hand, you can use snap ring pliers with a tip diameter of 0.047 in. to open the windscreen's retaining ring.
  5. If testing the left acoustic stub microphone, close and latch the SM5 to keep the lid out of the way.

    Depending on the size and shape of your calibrator, you may not be able to test the left stub microphone with the SM5's lid open.
  6. Follow the calibrator's instructions to power on the calibrator and insert the microphone.


  7. If your calibrator has controls to adjust its frequency and amplitude, select 1 kHz and 94 dB SPL.
  8. Read the signal level measurement on the SM5's display or in the mobile app to determine if the microphone has acceptable sensitivity.
    Important: Because different Song Meter models have different audio circuitry and settings, measuring the same microphone with different Song Meters may yield different results.