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Background. A truck with a 4-stroke diesel engine travels along a straight road with constant speed. Near the road is a microphone that senses the radiated acoustic noise from the truck during its passage past the microphone. The output of the microphone is sampled at the rate of 12,000 samples/second and 30 seconds of data are recorded during the truck’s transit which can be found in the attached file: truck.wav. During the recording of the data, the speed of sound propagation in air was a constant 347 m/s.

Problem: Assuming that the truck is a point source,

• Plot the spectrogram of the acoustic data file truck30sec.wav
• Given that the strongest spectral line is the engine firing rate, calculate the truck’s

(1) engine firing rate (in Hz),

(2) cylinder firing rate (in Hz),

(3) number of cylinders,

(5) speedometer reading (speed in km/hour),

(6) distance (in meters) of the closest point of approach of the truck to the sensor,

(7) time (in seconds) at which the closest point of approach occurs.

Your solution should detail your approach and reasoning to solve the problem, as well as your best estimates of the above parameters.

Send your solutions (with your contact details) to asa@aip.org by  July 31, 2014 with the subject line “Student Challenge Problem Entry.”

Cash awards of \$500 and \$250 will be awarded to the first and second place winners, respectively. Winners are invited to prepare and present a poster no larger than 4’ x 8’ at the 168th Meeting of the Acoustical Society of America in Indianapolis, Indiana, 27-31, October 2014. A travel subsidy will be available if needed.

Entrants need not be members of the ASA. All entries must be accompanied by proof of the entrant’s
status as a university student.

More details about the Student Challenge will be discussed in the summer 2014 issue of Acoustics Today which will be on line about June 16, 2014.

By entering this competition you are granting ASA the right to post your answer on any of its web sites including, but not limited to, AcousticalSociety.org and AcousticsToday.org.