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A problem in CoreAudio, Tiger’s new system-level sound manager, can cause iChat and other applications to stop producing sounds. I noticed it at first when iChat no longer alerted me to incoming messages with a lilting yoom. The solution seems to be to reset a background process called coreaudiod when it loses track of what sounds go where.

The problems crop up after the system has been running for some time. If you’ve noticed strange audible glitches, such as harsh digital belching noises or clipped alert sounds, you’ve probably heard the transition from “live audio” to “dead audio.” Only applications that were active at the time of the breakdown are affected, so some apps will continue making noise while others will not.

A preferences file tracks the various audio sources, including applications and devices, and their destination outputs. This file, for whatever reason, can become corrupt. I don’t know what causes this corruption, but the effect is that the sounds produced by some applications are directed into The Nothing, where those of us with ears cannot hear them.

One solution is simply to restart the machine. This clears the assignment of inputs and outputs, restarts the CoreAudio daemon, and restores sound playing for some time. But restarting sucks. So here’s the second solution.

You can reset the CoreAudio daemon manually, without restarting your computer, by following these three steps:

1. From your hard drive (not your home folder), open Library > Preferences, then move com.apple.audio.DeviceSettings.plist to the trash. Empty the trash to ensure it’s deleted.
2. Open Activity Monitor, which is in Applications > Utilities. Select the process called coreaudiod. I’ll bet you a a banana it’s in red text, and it’s listed as “(not responding).” Click the red stop sign in the toolbar, a button called “Quit Process.” Click “Quit” in the dialog to confirm. Enter your password to authorize. coreaudiod will die and re-start itself, re-creating the file you just threw in the trash.
3. Now you just have to quit and re-launch any apps that weren’t making noise. They’ll re-register with coreaudiod, and all will be well.

Unfortunately, this is not a permanent fix, but merely a remedy to the symptoms. You can repeat this procedure each time your audio dies. It saves the need to restart, but it doesn’t do much to prevent a recurrence.

With luck, Leopard will cure CoreAudio of its narcolepsy.

This entry was posted on Tuesday, August 29th, 2006 at 3:02 pm and is filed under Fixing things. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

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