Silently Adjust Sound Volume Level by Holding Down the Shift Key
You can adjust your Mac’s sound volume level silently by holding down the Shift key and then pressing the volume up or volume down keys. This complete silences the audio feedback of quacking and beeping as the sound goes up and down, allowing you to change the volume without creating a bunch of noise.
Remember, you have to hold down the Shift key each time you adjust volume to gain a result from this, it’s not a permanent change. This per-adjustment approach is really handy when you’re in a quiet office or library and don’t want the beep sounds blaring as you adjust system volume.