The PDMGen3_RK library supports PDM (pulse-density modulation) audio input on Gen 3 devices!
Because of limitations in the nRF52 I2S peripheral, common I2S microphones don’t work, but the PDM digital microphones like this one from Adafruit work great. PDM is best suited for voice applications as it’s pretty much limited to 16 kHz 16-bit audio on the nRF52. It uses the nRF52 hardware PDM decoder and DMA so the CPU isn’t burdened by the sampling.
The example code streams audio over Wi-Fi to a node.js server from an Argon. The server writes the files to disk as wav files.
There’s also an example that writes wav audio files to an SD card directly connected to your Gen 3 device.
Library and instructions here: https://github.com/rickkas7/PDMGen3_RK