Frequency Discrimination Lab

Background:

1. Purpose and Goals
   1. To further develop skills in using the scientific method
   2. To study one of the dimensions of auditory perception: discrimination
   3. To develop futher experience with difference thresholds
2. Frequency Discrimination
   1. Observations
      1. If two tones are to close together we hear them as the same. We call the lower frequency the base or standard frequency. The higher frequency is the test frequency.
      2. As the frequency moves farther apart, we can eventually hear the difference in frequencies
      3. This is a threshold, in fact a difference threshold or JND
      4. There are many frequencies we can hear (20 Hz to 20 KHz, at least for you folks)
   2. Question: how might these frequency discrimination thresholds differ if you test different base frequencies?
   3. Alternative Question: How might different methods, e.g., Method of Limits, Method of Constant Stimuli, etc, affect your threshold?
3. Experiments: Reminder
   1. Experiments involve:
      1. Independent Variable(s): the variable(s) the experimenter manipulates, in this case the frequency you are testing for threshold
      2. Dependent Variable: the variable the experimenter measures, in this case the size of the frequency difference at threshold (what type of threshold?)
      3. Control: Change only one thing at a time

The Experiment:

1. Equipment
   1. Back to the Chapter 2 in ISLE Software
   2. Use the Frequency Discrimination version of Method of Limit, Method of Constant Stimuli, or Forced Choice. Your choice.
   3. There are headphones available as well, you might need to use yours.  
      1. You will need to use them
2. Stimulus Settings Tab:
   1. Leave all the same except:
   2. Base or Standard Frequency.
      1. This is your I from Weber's Law
      2. Version 1: how might different frequencies impact thresholds?
      1. Week 1: Pick 5 frequencies covering a good part of the range of possible frequencies
      • We typically like to have more values closer together at in the lower part of the range
      • So we often double each value: 100 Hz, 200 Hz, 400 Hz, etc.
      • Make sure you cover a good part of the range
      2. Week 2: Pick 4 more frequencies that are between pairs of other frequencies, e.g., a frequency between your lowest and second lowest, then one betweens second and third lowest
         • Using the list above, you might test 150 Hz, then 300 Hz, etc.
      3. Version 2: How might different methods impact thresholds
      • Week 1:
      • Chose at least three of the methods from Chapter 2
      • One of which must be Forced Choice Methods
      • Test at least 2 frequencies
      • on Week 2, you will test a new frequencies
3. Method Settings Tab:
   1. Pick on of the three methods
      1. Method of Limtis, or
      2. Method of Constant Stimuli
      3. Method of Adjustment, or
      4. Forced Choice
   2. Choose the levels on the method settings you think will give you good data
4. Procedure:
   1. Most will depend upon the nature of your experiment
   2. Read the directions carefully
   3. There is one common element:
      1. two tones will play
   4. Listen carefully
   5. Good data quality is very important
5. Data
   1. The data will be the frequency difference that is just detected reliably in Hz
   2. What type of threshold is this?
   3. Determine your thresholds using the proper method
   4. Create a graph of them with frequency on the x-axis and your thresholds on the y axis.
6. Write-up: Brief Report
1. Graph and interpret your results. 
2. Short description of the procedure. remember that the procedure includes that your dependent variable is.