ARL: Startle Calibration Instructions

Instructions for Calibrating Startle Probe:

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.

Turn on the computer the generates the startle (in both labs, it is the computer that is on the right), and open up DMDX.

Once in DMDX, click browse, and follow this file path: local/calibrate/CalibrateLong.rtf

Select the CalibrateLong.rtf file, and hit run.

On the Mackie audio mixer, verify that the main mix and sub mix are on the indent/U.

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.

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 can not slip out of this position.

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.

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.

Once you are finished, return the sound meter to it's carrying case, and then to the shop.

Close DMDX, and shut down the computer.