Interference Challenge
The information below is subject to change as
more event tips and details are included. Please monitor this page
regularly.
Faculty coordinator: Professor Fred Becchetti [fdb@umich.edu].
Event Description:
Students
will place two sound producing speakers, operating between 300 and 2000 Hz (specific frequency will
be provided at the event), outside of a ring, of 1m diameter, in which there are two fixed microphones
(positions provided at the event). The students must endeavor to place the speakers in such a way to
create interference, such that the sound intensity at one microphone is at a maximum and the sound intensity
at the other is at a minimum. The teams are given a score based upon the registered sound intensities at the
microphones and upon a short quiz.
Note: If you have an issue with loud sounds, you should contact us or refrain from participating in this event.
Event Location and Time:
Intro Labs
10:30AM - 11:50AM and 1:00PM - 2:50PM
Apparatus and Materials:
-
2 microphones (not to be moved).
-
2 speakers (movable anywhere outside given circle).
-
A circle with a marked coordinate system and rulers.
-
Computer with tone generating program and decibel intensity meter.
Event Rules:
-
Every team must have two to three members.
-
Each team will have 20 minutes in which to complete the theoretical quiz.
-
Then, the coordinates of the microphones and the frequency are specified, and another 15 minutes are allowed
for the speaker position calculations.
-
Each team will then be given 2 minutes to place the speakers anywhere outside of the playing ring in order to
achieve (by interference) the maximum possible sound intensity at one microphone (labeled target) and
the minimum possible sound intensity at another microphone (labeled anti-target). Speakers are
turned off at this point.
-
The speakers are turned on and the microphones register two sound intensity values (Itarget, and Ianti-target).
-
Each team shall be given another 2 minutes in which to re-calculate and adjust/change the placement of
their speakers (speakers are again turned off).
-
The speakers are turned on and the intensity values are recorded. Teams may keep the scores from the better of their two trials.
Judging Criteria:
-
Experimental Score: k x (Itarget / Ianti-target). The constant k is being determined by the event team.
-
Theoretical Score is based on quiz results.
-
Final Score: Experimental Score + Theoretical Score
-
Gold, Silver, and Bronze Medals will be awarded to the teams with the highest three scores, respectively.
References:
The following materials will help you prepare for the quiz and with the calculations of positions:
Here are two links where you can download a free tone generator and a volume meter:
