Calibrate White Noise Startle Probes for HD280Pro
- Record the decibels before and after calibration in the Startle Probe Calibration Log
To do this task, you will need to get the sound meter from the shop. Ask for the bigger one, that is housed in a suitcase, and has a headphone holder.
Bring this sound meter into the room where participants receive startle probes.
On the Mackie audio mixer, verify that the sub mix are is the indent/U and the main mix, which controls RA speaker volume, is turned all the way to the right/max.
Verify that the computer volume never changes after initial calibration of the sound probe.
Pull the meter out of the suitcase and slip the metal sleeve over the meter.
The circular end of the meter should slip into a round opening at the top of the metal sleeve.
Turn the meter dials as follows:
- The db range should be set to 100.
- The Batt dial should be set to A on the slow side.
- The frequency dial should be set to 250.
Pull the Batt dial out- (this turns the device on).
Loosen the wing nuts until you can move the metal arm on the top of the metal sleeve.
Slip one headphone in between the metal arm, and metal sleeve. The headphone should surround the round opening at the top of the metal sleeve.
Tighten the wing nuts so that the headphone cannot slip out of this position however do NOT tighten the wing nuts such that the cushion on the headphone is pressed. The headphone cushion should be fully expanded as in the picture.
Turn on the computer that generates the startle (in both labs, it is the computer that is on the right), and open up DMDX or Matlab depending on how you control your stimulus presentation.
If using DMDX, click browse, and follow this file path: local/calibrate/CalibrateLong.rtf Select the CalibrateLong.rtf file, and hit run.
If using Matlab, type “CalibrateWhiteNoise” and hit Enter.
Now, hit the space bar to initiate the long probe.
Move quickly back to the sound meter, and check where the decibel needle is pointing. The goal is to get the needle to point to 2.
If the needle is not pointing towards 2, you will need to adjust the 5-6 gain dial on the audio mixer.
Check both headphones (left and right) and make sure both are outputting at 2.
For DMDX: If the probe ends before you can adjust the needle accurately enough, hit escape to get out of the file, do not save the data, and run the long startle probe calibration file again.
For Matlab: If the probe ends before you can adjust the needle accurately enough, hit “enter” and type “CalibrateWhiteNoise” and hit enter again.
Once you are finished Close DMDX or Matlab and shut down the computer.
Make sure to turn the sound meter off by pushing the batt dial back in. (if you do not- the battery will die)
Return the sound meter to its carrying case, and then to the shop.