The ears of a healthy young adult hear frequencies in the range of 20 to 20,000 Hz. While you cannot perceive sounds with higher frequencies, you can feel those with lower frequencies. Instruments such as bass drums and phenomena like explosions and thunder produce inaudible low frequencies, called infrasound, in addition to those you hear. Subwoofers are speakers designed to reproduce these frequencies, adding realism to movies, video games and other media. By connecting a variable-frequency sine-wave oscillator to a self-amplified subwoofer, you can produce infrasound.
- Signal generator or oscillator
- Self-amplified subwoofer
- BNC female to RCA male adapter cable
Turn on the subwoofer and oscillator. Turn the oscillator’s output amplitude control all the way down. Adjust the oscillator’s frequency to 10 Hz. Set the subwoofer’s output knob to its minimum.
Attach the BNC female connector to the BNC male on the oscillator. Connect the RCA male plug to an RCA input on the subwoofer.
Adjust the subwoofer’s output to about one-quarter to one-half its maximum.
Slowly turn up the oscillator’s amplitude. You will begin to feel infrasound vibrations from the subwoofer. Slowly increase the oscillator’s frequency. Notice as you pass roughly 20 Hz, the subwoofer's output changes from vibrations you feel to those you hear as a low-frequency pitch.
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