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Are Two Ears are Better than One? Binaural vs. Monaural Sound Localization 

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Author: Peggy LaCerra, Ph.D.

Humans use both "monaural" (one ear) information and "binaural" (two ear) information in order to locate (or "localize"), people, animals, and noisey things. In this experiment, blindfolded subjects will be assigned to one of two groups. Group One, the "monaural group," will guess the location of a kitchen timer when it rings with one ear blocked by an ear plug. Group Two, the "binaural group," will guess the location of the timer with both ears. You can then compare the accuracy of the guesses in each group.

Problem:

How do we localize objects and beings in space through sound?

Materials:

  • Kitchen timer
  • Blindfold or eye mask
  • Wax ear plugs
  • Painter’s tape
  • Protractor
  • Yard/meter stick
  • Felt-tip pen
  • Paper and pen

Procedure:

  1. Create two data sheets, one labeled “Group One” and the other “Group Two.” On both sheets, create two columns, one labeled “Subject #” and one labeled “Number of Rays Off.”
  2. Place a chair in a room, leaving a semi-circular space with a radius of 10’ to 12’ in front of and to the sides of the chair.
  3. In front of the chair, use the protractor and the painter’s tape to create nine 20-degree rays from the chair to the walls of the room. Use the felt tip pen (on the tape) to number the rays one through nine.
  4. For Group One, ask the first subject to sit in the chair. Fit an earplug snuggly into one of their ears and put the blindfold on.
  5. Take the timer to one of the rays and set off the alarm.
  6. Moving away from that ray and toward the subject, ask the subject to remove the blindfold and point to the ray nearest the location where they think the alarm sound originated.
  7. On your data sheet, note the number of rays (and the number of degrees) the subject’s guess was from the actual location. (Note: the number of degrees is the number of rays multiplied by 20 degrees.)
  8. Repeat with other subjects in Group One.
  9. Repeat the same procedure with the subjects in Group Two, who will not wear the earplug.
  10. Calculate the average number rays off for Group One vs. Group Two, and multiply each of the two averages by 20 degrees to get the average number of degrees off target.
  11. Create a bar graph for the number of degrees off target for each group. Label the bar for Group One “The Monaural Group”, and the bar for Group Two “The Binaural Group”; remember to label the graph itself.
  12. Write a discussion of the results that addresses the research questions.
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