These steps assume you have at least Shush 1.2.1 installed.

1. Quit Shush.
2. Launch the Teriminal application.
3. Paste the following command, as a single line, then press Enter.

defaults write -app Shush blacklist -array-add "com_globaldelight_driver_Boom2Device:Boom2Device"

4. Restart Shush.

Shush should no longer mute the Boom 2 audio device, but if you still can't hear any audio, then your Boom device is currently muted.

How to Unmute Boom

Launch the Audio MIDI Setup application.

1. Choose the Boom2Device.
2. Click the Input tab.
3. Make sure the Mute box is unchecked.