How does the size of a speaker box change the sound it produces at different frequencies? You build three sealed plywood enclosures with depths of 500 mm, 400 mm, and 300 mm. Each one holds the same 8-inch speaker.
You play test tones at 30 Hz, 50 Hz, 80 Hz, 150 Hz, 300 Hz, and 600 Hz through each enclosure. A decibel meter placed one meter away records the volume at each frequency.
The data shows whether smaller boxes boost certain frequencies above the baseline level that larger boxes keep flat.
Hypothesis
The hypothesis is that reducing the size of the speaker enclosure will cause the dB of some frequencies to be higher compared to the rest of the frequencies.
Speaker enclosure size shapes the sound you hear at specific frequencies. Different box depths boost or flatten the volume at certain points in the range. You build three sealed plywood enclosures with depths of 500 mm, 400 mm, and 300 mm, then play test tones from 30 Hz to 600 Hz through each one. A decibel meter placed one meter away records whether smaller boxes raise the dB level above the baseline that larger boxes keep flat.
Sound waves vibrate at different frequencies, and the enclosure around a speaker shapes how those vibrations reach your ears. To measure this, three sealed plywood enclosures — 500 mm, 400 mm, and 300 mm deep — each hold the same 8-inch speaker. Test tones from 30 Hz to 600 Hz play through each box in turn. A decibel meter placed one meter away records the volume at each frequency. Smaller boxes boost certain frequencies above the flat baseline that larger boxes maintain, and the data makes those differences visible.
Method & Materials
You will construct three speaker enclosures of different sizes using plywood, glue, nails, and silicon filler. You will then connect the speakers to a CD player and measure the decibel reading of various audio frequencies using a decibel meter.
You will need plywood, glue, nails, silicon filler, three 8-inch speakers, an electric drill and drill bits, a saw, a decibel meter, a CD player, and a test CD with various audio frequencies.
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The results showed that the frequency response of the two larger speakers did not go beyond the 0 dB level, but the smallest speaker produced some frequencies that were louder than the others. These frequencies showed a response reading higher than 0dB.
Why do this project?
This science project is interesting because it demonstrates how the size of a speaker affects its frequency response.
Also Consider
Experiment variations could include testing different types and thicknesses of wood for the enclosure, or testing different sizes of speakers.
Full project details
Additional information and source material for this project are available below.
