MAX9814 Microphone Sound Level

Electret microphone with automatic gain control. Analog output converted to dB SPL approximation via ADC.

Sensor Maxim Integrated MAX9814 acoustic analog Draft

This entry is draft and has not been confirmed against physical hardware. A conforming tool will refuse to provision it. The datasheet is the authority, not this page.

Specifications

Protocol analog
Sensor type acoustic
Manufacturer Maxim Integrated
Model number MAX9814
Datasheet url https://datasheets.maximintegrated.com/en/ds/MAX9814.pdf
Read interval seconds 5

Readings

SlugDevice classUnitRange
sound-level sound_pressure dB 40 to 120

Wiring

PinRequiredNotes
out Yes Analog audio output centred on a DC bias. The Raspberry Pi has no ADC, so an external converter is mandatory.
gain Optional Floating selects 60dB, tied to ground 50dB, tied to supply 40dB.
ar Optional Sets the automatic gain control attack and release ratio.

Supply: 3.3V or 5V

Failure modes

  • The Raspberry Pi has no analog input. This part cannot be connected without an external ADC, which is a separate component and must be declared.
  • The output is an audio waveform, not a level. A sound level requires sampling a window and computing RMS. A single ADC reading returns an arbitrary point on the waveform and is meaningless.
  • An ADS1115 at its maximum sample rate is far below audio bandwidth. It can track a slow envelope but cannot reconstruct the signal, so the derived level is an approximation of loudness only.
  • Automatic gain control continuously changes the amplifier gain, so absolute amplitude does not correspond to absolute sound pressure. Comparisons across time are only valid while the AGC is not moving.
  • Decibel output requires calibration against a reference meter per installation. Without that constant the published value is relative, not sound pressure level.

Entry

Keymax9814
StatusDraft
Revision1
Registry0.3.0
Datasheet Entry on GitHub JSON for agents

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