Who Can Hear Monte Tone? Lab
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The Following Information is Provided to the Student
Question: What is the relative loudness of sound which results when sound from two sources are heard at a given seat location of an automobile?
Purpose: To analyze the interaction of sound waves from two speakers of an automobile in order to determine which seat locations in the automobile would experience constructive and destructive interference.
A complete lab write-up includes a Title, a Purpose, a Data section, and a Conclusion/Discussion of Results. The data section should include the provided diagram (taped in) of the car with the indicated vehicle number and wave pattern letter. A table of data should be included indicating the part of each wave (compression or rarefaction) which reaches a given seat location and the resulting type of interference which results. The Conclusion/Discussion describes the relative loudness of sound which is heard at each indicated seat location. A short explanation is given for why the relative loudness is high or low at a given location.
Scoring Ruberic
| S11. | Who Can Hear Monte Tone? Lab | Score |
|---|---|---|
| _____ | Included, labeled and organized all parts of the lab report. | _____ / _____ |
| _____ | Data section includes the provided diagram (completed and taped in); the vehicle number and wave letter is indicated. A table of data summarizing the results is provided; indicated the seat location, the part of each wave which interfered at the seat location and the type of interference which results. | |
| _____ | Conclusion/Discussion described the relative loudness of sound heard for each seat location. A short explanation is given for why the sound is heard as soft (minimum) or loud (maximum); discussion reveals understanding. |
Lab Details
Materials Required
Diagram of vehicle and wave patterns (provided); transparencies; copy machine.
Description of Procedure
Each student is given a diagram of a car with several marked passenger locations and two speaker locations. A couple of transparency strips consisting of a wave pattern are provided for each student. Students line up the wave patterns with the source (the speakers) and manipulate their orientation to determine the type of interference which is encountered at each passenger location.
Safety Concerns
There is always a higher than usual level of risk associated with working in a science lab. Teachers should be aware of this and take the necessary precautions to insure that working environment is as safe as possible. Student horseplay (especially the use of meter sticks as swords) and off-task behaviors should not be tolerated.
Suggestions, Precautions, Notes
- The PDF file for the Auxiliery items provides all the materials which students need.
- This lab is a great introduction to the early labs in the Light and Color. Those labs pertain to the topic of two-point source interference.
- A great follow-up demonstration can be performed using two speakers connected to a digital function generator. Space the speakers about 1-meter apart and set the function generator to produce a 1000 Hz signal. Students can stand about 5 to 10 meters away and walk parallel to the imaginary line which connects the speakers. As they walk slowly (with one ear covered), they should observe positions of minimum and maximum loudness along the line at which they are walking. The demonstration works best in an open space with minimal reflecting surfaces (e.g., on a football field).
Links
Connections to The Physics Classroom Tutorial:
The following reading is a suitable accompaniment to this lab:
http://www.physicsclassroom.com/Class/sound/u11l3a.cfm