| Before the advent of electronic spectrum analyzers, Helmholtz Resonators were used to detect different frequencies in a sound wave. This set of nineteen resonators was purchased for $70. Both date of purchase and manufacturer are unknown. |
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| Before the advent of electronic spectrum analyzers, Helmholtz Resonators were used to detect different frequencies in a sound wave. This set of nineteen resonators was purchased for $70. Both date of purchase and manufacturer are unknown. |
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