There is no option to disable Toolbox sound output that I can find on MacOS, and disabling system sound effects in Sound preferences does not defeat it on my system (MacOS 10.14.4). It is possible to use a dead-end audio output, but like disabling sound effects, this also disables desired system sound. Toolbox features are great, but having it make sound when not desired is incredibly disruptive for people like me who work with music and audio. I hope this feature can be added as it would be a subtle but very significant improvement. Thanks!