Identifying the type of noise
You may hear two types of noise—acoustic and digital. Acoustic noise is the sound you hear coming directly from the computer's power supply. Digital noise is sound heard in the audio signal when you have AC-powered audio devices, such as a mixer and amplifier, connected to your computer's analog or digital ports (USB, FireWire, PCI, audio input port, optical audio port, and so on). Here's a look at both types of noises.
If the power supply itself is making sounds, this is acoustic noise. This seems to occur most often when you're not using your computer much, and the microprocessors idle down to conserve energy. However, the noise can also occur during heavy network activity or when you're moving icons around on the desktop.
The following WAV files were recorded by a customer as an example of typical acoustic noise you'll hear from a Power Mac G5. The computer's speakers were unplugged and audio was muted.
This first audio file is of the computer idling.
The second audio file is the same computer during heavy network access. Some "chirping" is more audible.
The third audio file is the same computer running OpenGL Cinebench tests. You can hear a high-pitched beep periodically.
If you have self-grounded, AC-powered audio devices connected to your computer and hear noise in the audio signal, this is digital noise.
Note: The computer's internal speaker and connected headphones are not affected as they are not self-grounded devices.
What you can do
If you're hearing noise, first find out if the noise is coming directly from the power supply (analog noise) or is in the audio signal (digital noise) by following these steps:
- Disconnect all peripherals from your computer except for the display, keyboard, and mouse.
- Try to reproduce the noise.
- If the noise appears to be coming from the power supply, go to the Acoustic section below for some troubleshooting tips.
- If the noise is no longer present, go to the Digital section below for some troubleshooting tips.
- Try changing the processor performance in Energy Saver preferences, which may reduce—but not eliminate—the noise. From the Apple menu, choose System Preferences, then click Energy Saver. Click the Options tab and from the Processor Performance pop-up menu, choose a different option than your current one: Automatic, Highest, or Reduced. Experiment with each of these settings to see which provides the most noise level reduction. Please note that choosing Highest may increase fan noise.
- For some first generation Power Mac G5 dual 1.8GHz or 2GHz computers whose serial numbers are between XX322XXXXXX and XX406XXXXXX, replacing the power supply may reduce—but not eliminate—the acoustic noise levels. If you have one of these computers, an Apple Authorized Service Provider can determine whether your power supply is eligible for replacement.
- For all other Power Mac G5 computers, it is not necessary to replace the power supply as this will have no impact on the noise levels. Try adjusting the Energy Saver preferences as noted above for the best results.
- If your computer is in a studio environment that contains many powered devices that are connected to each other, proper grounding is essential to truly eliminate noise issues. Please see our audio noise troubleshooting guide, "Solutions for Noise in the Audio Signal," to learn about proper grounding techniques that can help you eliminate noise. Make sure that you follow all of the suggested steps to rule out your equipment and cables as the source of interference.
- If you have a Power Mac G5 dual 2GHz or 1.8GHz computer and the steps in our audio troubleshooting guide do not resolve the issue, Apple is willing to replace the power supply for customers who are dissatisfied. Replacing the power supply will help reduce the occurrence of digital noise, but when you connect audio equipment to the computer, be sure that you properly ground everything to truly eliminate noise. Please contact an Apple Authorized Service Provider to determine whether your computer's power supply is eligible for replacement.
- For all other Power Mac G5 computers, it is not necessary to replace the power supply as this will have no impact on the noise levels. Try reviewing the troubleshooting guide again and, if necessary, contact an Apple Authorized Service Provider for additional troubleshooting assistance.