Loudspeaker Resonator

Challenge: To build a simple resonator that will produce the loudest amplification possible.

Parameters: The resonator will begin with a provided 555 chip and 9 V battery. The circuit will be built with help from Mr. J. You will be required to design a resonator that will increase the output sound level as much as possible.

Scoring: Your system will be scored based on the factor by which your resonator increases the decibel level of sound produced, as measured one meter from your resonator.

Score = (Decibel reading with resonator) / (Decibel reading without resonator)

Your speaker must be on the table, and your resonator must be a removable object that does not exceed dimensions of 50 cm in any direction from the speaker. The output of your speaker must be a minimum of 30 dB without the resonator.

Rank will be based on score, with highest score earning highest rank.

Physics: The circuitry in the 555 chip is beyond our curriculum, but interesting. The basic physics of resistance, current, voltage, and capacitance should be understood for the parts of the circuit outside the chip. The production and propagation of sound waves, and the frequency (pitch), are related to kinematics, dynamics, and wave propagation. The amplitude and sound level can be improved by having a resonator. Your journals MUST include a detailed model that demonstrates your understanding of the physics involved.

Extensions: The tone generator frequency is controlled by the resistance of part of the circuit. That resistance can be a variable resistor (potentiometer), allowing you to precisely control the frequency. The resonator will probably produce several frequencies in different proportions that depends on many, many factors in addition to the driving frequency.

Help/Hints: Make sure you have an app on your phone that allows you to measure pitch and sound level (Sci Journal and PhyPhox are excellent and free)

Quiz Topics: Simple circuitry (voltage, resistance, current, capacitance), waves, sound.

Online Text: 13, 14, 18.5