Doesn't work when headphones plugged in

[raafirivero]

I'm on MacOS Sierra - the script works fine, and my Mac boots silently, when nothing's plugged into the headphone jack. But I regularly leave headphones in at my office environment. And the chime always goes off when they're in.

[matteoacrossi]

Unfortunately this is a known issue. When you plug in headphones the OS, the volume control only affects the the headphone volume. So the script mutes the headphones. But at boot the audio is output to the speakers and this is why you hear the chime.
There doesn't seem to be a solution with Applescript (on which my script is based). A compiled program is needed to overcome this limitation. I might try to delve into this sooner or later...