No sound Mac Pro 4,1 Yosemite

You're wasting your time addressing Apple here. Do you want to try to solve the problem?

When the sound goes out, note the exact time: hour, minute, second.

These instructions must be carried out as an administrator. If you have only one user account, you are the administrator.

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

The title of the Console window should be All Messages. If it isn't, select

SYSTEM LOG QUERIES ▹ All Messages

from the log list on the left. If you don't see that list, select

View ▹ Show Log List

from the menu bar at the top of the screen.

Each message in the log begins with the date and time when it was entered. Scroll back to the time you noted above.

Select the messages entered from then until the end of the episode, or until they start to repeat, whichever comes first.

Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message by pressing command-V.

The log contains a vast amount of information, almost all of it useless for solving any particular problem. When posting a log extract, be selective. A few dozen lines are almost always more than enough.

Please don't indiscriminately dump thousands of lines from the log into this discussion.

Please don't post screenshots of log messages—post the text.

Some private information, such as your name, may appear in the log. Anonymize before posting.

I have to echo what Mr. Davis wrote here: Apple does not actively look at/review what goes on here-it's more of a user-to-user forum. That being said, have you tried the following: PRAM zap-reboot computer, hold down Apple+Option+P+R while rebooting until you hear 2-3 "bongs", then let go of the keys,

repairing permissions-get Disk utility running, verify and repair permissions from that.

Audio MIDI-maybe something got stuck. Find Audio MIDI and see what your sound output settings are.

other than that, try resetting the PMU/SMC, which you can find out how to do here or by going to Apple's main support section

Although I may have had a few bugs with Yosemite, overall no huge problems. I have a Mac pro 3,1, which is, I'm sure older

Other than that-maybe think about reinstalling Yosemite. I'm sure that if you are patient, you will find an answer here, or your bug will be fixed.

JB

You could try installing the 10.10.3 combo update

OS X Yosemite 10.10.3 Combo Update

Like always, make sure you have a backup.