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Start with the slow lookup in Using tools. The local /voice playground has a Thinking sound while tools run checkbox. This adds a quiet keyboard loop to a tool’s waiting period.

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Try it without changing Python

  1. Run the tool example and open /voice on your local server.
  2. Enable Thinking sound while tools run in the sound controls.
  3. Start a session and ask “Check order 101.”
  4. Listen for typing during the lookup and for it to stop when the answer begins.
  5. Disable the checkbox and repeat to compare the quiet gap.
The checkbox defaults to off on a fresh browser and is remembered in that browser’s local storage. It uses the typing ambience asset fetched from /voice/ambience/typing. The asset is downloaded on first use.

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When it plays

The playground starts the loop on agent_status when a tool call is reported. It stops on reply text or speech audio, interruption, a request for approval/input, or disconnect. A spoken filler can also stop it when that speech begins. A fast tool may finish before the asset is loaded or any loop is audible. This sound indicates tool activity. It does not play throughout every LLM reasoning step and does not make the tool complete sooner.

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Where it works

The sound is played locally by the browser. There is no voice_config.thinking_sound field, and enabling the checkbox does not add typing audio to Twilio, Telnyx, or another caller’s media stream. The playground’s platform target also needs an accessible ambience asset source; its local helper skips fetching when no voice HTTP base is available. A custom client can implement its own sound using the same event lifecycle. Stop and discard it when the session pauses or ends, and when speech begins. Browser-generated typing is not provider-generated speech and is not included in the server’s PCM recording. Spoken fillers are the next step when you want the assistant itself to say something while a tool is running. For a continuous background track, see Background audio.