Lab 3: The Synthetic Psychology of Sound LocalizationReturn to the lab overview, or move on to task 2.
Task 1: A psychology experiment
To begin with, we are going to do an experiment to measure our ability to localize sound and the physical stimulus cues we use to do this. To perform the lab you need:
- 1 printout of this protractor paper
- a permanent marker (Sharpie)
- 1 sheet of transparency per group member
- a computer or smartphone with internet access and the ability to play .wav files
- a pair of headphones
Each member of your group should perform the experiment. Each group member should lay the transparency paper over the "protractor paper" linked above or given by the instructor so that the protractors are visible through the transparency.
The experiment will consist of two parts. In both phases you will listen to a sequence of sounds over your headphones. Each sound will be numbered. You should close your eyes while listening to the sound. You can repeat the sound as many times as you like by clicking play. Your task is to estimate where the sound is emitting from if it were in front of you. After you are confident that you have heard the sound, mark on the transparency the relative location where you heard the sound with the sound's number. At the end of each part of the experiment your sheet should look something like this (of course you should write the numbers where you feel appropriate):
After each member of your group has performed Experiment A and B, take the overhead transparencies from each group member a lay them on top of one another. Are there any pattern in the placement of the numbers as a function of angle?
Stimulus Set 1
Listen to each item as long as you need, then indicate your response on the transparency.
Stimulus Set 2
Listen to each item as long as you need, then indicate your response on the transparency (turn the sheet first).
After each member of your group has performed the experiment, answer the following questions, then continue to the next step.
Q1: Describe the subjective experience of being in the experiment. What did you perceive?
Q2: How did the results of your individual group members compare? Was their agreement about the location of the sources in space?
Q3: Check out this link and listen to the recording in headphones. This is called a stereo image. In this case, processing of the sounds was done via a computer which moves the sound around in 3D audio space. Demos like this indicate how much we understand about how our ears and brains create a 3D representation of sound in the environment. We can manipulate the cues we know your brain uses to trick you into hearing 3D sounds that are created artificially. Now, listen to the same sound, this time without wearing headphone. How does it compare? Why do you think there might be a difference between listening with headphones versus listening with speakers?