Check your Sound System Preferences pane
1. Remove any external audio devices and cables from the USB, FireWire, or 3.5 mm audio ports.
2. Open System Preferences from the Apple menu, the Dock, or from the Applications folder on your hard drive.
3. Open the Sound pane and the Output tab, then select Internal Speakers as in this image:
- If Internal Speakers is not an option proceed to step 4. For Mac Pro computers, proceed to step 5.
- If Internal Speakers is present but not selected, select it and test again.
- If the Output volume slider is low or the Mute box is selected, raise the volume slider or deselect the Mute box and test again.
- If the issue continues through these steps and Internal Speakers remains the selected option proceed to step 5.
4. If the Internal Speakers option does not appear in the Output tab and your computer is not a Mac Pro, check that Digital Out is present as in the image below.
- Confirm again that all external audio devices and cables have been removed.
- Check to see if a red light is lit in the line-out port. If so, your Apple computer may need service.
- If you do not see a red light, proceed to step 5.
5. If the issues persist, contact Apple support for further troubleshooting assistance.
Please don't forget to rate me answer with one of the top three ratings, as this is the only way that I receive credit for my time and answer.
Have a nice Labor Day Weekend.
Thank You, Dan