Graphical elicitation test for the source-related width in a concert hall

Prerequisites:

1. Install the CH340 USB-Serial driver. Instructions for Mac and Windows are available here: https://sparks.gogo.co.nz/ch340.html
2. Install Max/MSP: https://cycling74.com/downloads You don't need a subscription in order to run the test. After the 30 day trial you can still run any patch but without being able to save.

Windows users

For the binauralisation functions to work, you will need to place some extra DLL files in your Max install folder. These are in the "Windows Dependencies" folder of the latest release. Depending on the bit-ness you use, these should be placed in either:

• "C:\Program Files (x86)\Cycling '74\Max" for 32-bit Max,
• "C:\Program Files\Cycling '74\Max" for 64-bit Max.

Calibrating the playback level

• Before you start the test, you need to calibrate the playback level of your audio interface using the calibration file handrubbing_calibrated.wav, which is included on the top level of the "ObjectiveGradingTest" folder.
• The file is a recording of hands rubbed at a high strength and moderately high speed.

1. Play the file over the headphones for a few seconds.
2. Take the headphones off, and rub your hands up and down, right in front of your nose, with both hands pointing straight up. Do this at a similar speed to what you hear in the recording.
3. Repeat the above process to compare the recording and your own hand rubbing sound in terms of perceived loudness, and adjust the playback level of your audio interface to match the loudness.

Opening the test

To launch the listening test please locate the "SourceWidthTest.maxproj" and open it using Max. Please note that the test will take a few moments to load, sometimes even up to more than a minute.

Connecting the head tracker to Max

1. Connect the head tracker to the computer using a USB-Mini-B cable.
2. Locate the "Head Tracking" section in the upper-left corner of the Max patch.
3. Select the "wchusbserial1410" (for Mac) or "COMxx" (for Windows, depending on the serial port used for the tracker) option in the dropdown menu; If you can not find the option, press the refresh button and it should now appear. If it still does not appear please make sure that you installed the CH340 drivers correctly and logged out or restarted the machine such that changes were applied.
4. Activate the head tracking by pressing the "Tracker On/Off" button.

Calibrating the head tracker

• Every time you mount the head tracker to a new position you need to follow the following steps in order to calibrate the head tracker.
• Please note that the head tracker might be drifting during the first minutes of operation. If this is the case, move the head tracker in an figure-of-eight motion for a little bit of time. Alternatively, leave the tracker powered on for a while until it no longer drifts.

1. Position your head looking straight ahead at your screen.
2. Press the button located on top of the head tracker for longer than 1 second.
3. Position you head again to look down at the floor.
4. Short-press the calibration button (< 1s).

• Now the head tracker is calibrated for the specific position it is currently mounted. It is recommended you do follow these steps every time you start a test or take the headphones off.

• If the tracker starts drifting after a while, you can always press the button shortly (< 1s) to re-centre.

• Locate the position indicator in the top-centre of the Max patch. This will show you when to reposition your head if it goes out of the +/- 7° range.

• The green indicator tells you that that your head is in the central position.

• The two red arrows will indicate in which direction to rotate your head such that it is in the central position again.

Running the listening test

1. Make sure you have selected your audio interface as an output device and set the sampling rate to 48kHz from the "Options -> Audio Status" menu.
2. Make sure the "Audio On/Off" button is active.
3. Type your surname in the name box. Please don't include any special characters in this field:
4. Press the "Randomize" button. This will randomize the listening positions in the test interface.

You can now click on each listening position labelled with "A","B","C" or "D" in order to listen to the specific stimulus. Alternatively, you can use the keyboard arrows to navigate through the positions.