Simple equalization can extend the low-frequency response of an electret microphone down to well under 1 Hz

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Other Materials from the Main Document

• Article «Revealing the infrasonic underworld cheaply. Part 1 - Seeking a solution»
• Figure 1. Simple equalization can extend the low-frequency response of an electret microphone down to well under 1 Hz
• Figure 2. The response of Figure 1's circuit to air-pressure changes at different frequencies
• Figure 4. A circuit that simulates an electret microphone in real life
• Figure 5. A few milliseconds of over-voltage applied across the mic at start-up injects enough charge to counterbalance much of the FET's longer-term start-up drift
• Figure 7. One LED lights up on positive swings and the other on negative ones, the intensities being proportional to the signal levels