For more advanced users, Terra offers the ability to customize the audio settings. This article explains what Automatic Gain Control (AGC) does and how to adjust it.
All of your Terra Station's audio controls are in the Terra Listens app: tap your Terra Station and open Settings. (The same controls are available on the terralistens.com website.) Changes apply directly — turning AGC off does not require a reboot.
The Terra has two analog microphones in a binaural configuration, to closely model the human listening experience. Each microphone goes through a separate amplifier stage with a configurable gain level, and then into an Analog-to-Digital Converter (ADC), where the audio can be recorded and processed.
Ambient listening devices like Terra are subject to a very large dynamic range of sound. Terra can detect very faint sounds, but can also automatically adjust to loud ones — that's what AGC does. Too much gain during loud events causes clipping, an unpleasant buffeting sound; too much amplification of quiet periods raises unwanted ambient noise; too little gain makes the soundscape very quiet, hurting both listening and Terra's bird-identification range. AGC continuously balances these.
Terra's digital audio circuitry uses stereo 16-bit 48kHz sampling, and the gain control can be adjusted between 0 and a maximum of 256. Each channel — left and right — is treated separately, which handles asymmetric sound like wind buffeting one microphone but not the other, or a loud bird next to one side.
AGC may not behave well in all conditions — it can introduce static, microphones cutting in and out, or other noise artifacts. If you're having sound-quality issues, turning AGC off is a very good place to start: tap your Terra Station in the app, open Settings, and switch AGC off. With AGC disabled, the Terra keeps one steady gain level, which you can set yourself.
If the sound still has issues with AGC off, contact us at support@terra.zohodesk.com.