Reader Kenneth Walsh's Mac has gone strangely quiet. He writes:
I woke my MacBook Pro from sleep today and when I tried to play an iTunes track the Mac made no sound. I then noticed that the sound icon in the menu bar was gray. I went to the Sound system preference and it showed Digital Out in the output area and no listing for the Mac's internal speakers. What the heck?
The background on the issue is that there's a small sensor switch inside the headphone port. When you insert a headphone jack, the sensor understands what's what and changes the sound output setting to Headphones. If you insert a jack for digital audio output, the device changes to Digital Out. When you remove the jack completely, it should read Internal Speakers.
The spirits tell me that there's a very good chance that you recently had something jacked into this port--a set of headphones or a cable leading to powered speakers, for example. When you removed the jack, something in the port prevented the sensor from tripping correctly. That's why you see Digital Out instead of internal Speakers.
The solution is to force the sensor to do its job. The safest way to do that is to simply run a jack in and out of the port a few times. Much of the time, this takes care of the problem by correctly tripping the sensor. If that doesn't work, there may be gunk in the port. Before turning to more invasive techniques, get a can of compressed air, attach the small tube that fits the nozzle, and blast a few shots of air into the port. With any luck, that should dislodge the gunk and the port will operate as it should.
If that doesn't work, find a foam-tipped swab that fits (electronics shops generally carry them), dip it in rubbing alcohol, and gently insert it into the headphone port in an attempt to wipe away any stubborn gunk. I recommend foam rather than cotton swabs because the cotton variety might leave threads behind. (This same technique works well with misbehaving headphone ports on devices such as iOS devices.)
It's possible that gunk has nothing to do with it. Rather, it may be that the switch just needs a subtle nudge. If a jack or swab doesn't work, I've heard of people successfully resetting it with a deft poke of a toothpick.
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