Here’s how to access a secret setting to make your Mac’s volume very quiet indeed—ideal if you’re trying to listen to something in a very quiet room where somebody else is working or sleeping, for example. As a tip this can be filed under the category, “Cool! I never knew that!”.
If your Mac has built-in speakers, you’ll be familiar with altering the volume using keyboard shortcuts (usually via the F11 and F12 keys). What you probably don’t know is that there’s a secret ultra-low volume setting. To access it, press the volume decrease hotkey until the sound is muted (that is, the speaker icon onscreen is struck through). Now press the actual mute hotkey (usually F10). You’ll see that the volume level is set at no bars. However, the sound isn’t muted. In fact, it’s a notch quieter than the lowest setting usually allowed—enough to hear things in a very quiet room.
This way you can still hear new mail notifications, for example, without the worry that somebody will complain about the noise!