The Android System dampens the audio volume of other apps due to how Noice handles the audio focus.
The following is an excerpt from the official guide explaining the audio focus.
Two or more Android apps can play audio to the same output stream simultaneously, and the system mixes everything together. While this is technically impressive, it can be very aggravating to a user. To avoid every music app playing at the same time, Android introduces the idea of audio focus. Only one app can hold audio focus at a time.
Before playing any sounds, Noice requests transient audio focus from the Android system. Apps generally use it to play short audio (notification sounds). When Noice requests it, the Android system asks the current audio focus holder app to duck (lower) its volume. Noice, by default, leverages this behaviour to play its audio alongside other apps.
The Android System recommends that apps acquire audio focus before playing audio, but it is not mandatory. You can enable Ignore audio focus change option to prevent Noice from dampening the audio volume of other apps.
Enabling this option prevents Noice from requesting audio focus from the Android System. The Android System still allows Noice to play audio, but it will not notify Noice when other apps play audio. Hence, other apps can play their audio completely unaware of Noice and vice versa. This behaviour may be undesirable in some cases. Therefore, we do not recommend it. To enable it, follow the steps below.
- Navigate to the Account tab from the bottom bar.
- Click the Settings option in the App category from the Account screen.
- Enable the Ignore audio focus change option under the Behaviour category.