audioOS 9.9.15.4.1 (build 19L452) is an official Apple over-the-air update for the HomePod, released on 2022-03-31T17:16:01Z. The update package is 486.6 MB. This is a delta (partial) update that requires 15.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: cbf95977f6551f51843013a2a0f9de8878eda88d.zip.