If you use HDMI or DisplayPort while connecting a Mac device to a display, you can have some problems with volume controls. It is clear that you can have some complications with different Mac models that are hard to resolve.
This article describes how to enable Mac volume control for HDMI or DisplayPort audio. Firstly you can try such steps:
1) Click the Apple icon at the upper left of your screen.
2) Click "System Preferences", then click "Sound" on the pane in Fig1-a below.
You can see that Fig1-a - System Preferences with Sound selected If both HDMI and DisplayPort are connected, select "HDMI" or "DisplayPort Audio" tab respectively.
And Fig1-b - Volume Control for HDMI settings.
Also, you can try the SoundFlower audio driver to control audio volume with a Mac keyboard or other devices.
The first step is to turn on the "Reduce volume on open" check box in Fig2 (SoundFlower) above. The second step is to click the Close button of the System Preferences window. After this, Mac OS X starts to reduce the Mac device's output sound volume when it is opened like iTunes, DVD player, etc, and you can adjust a Mac speaker sound level by using Mac OS-X menu bar > Apple icon > System Preferences > Sound or Built-in input/audio devices selectors.
Another option is Fig3 - Volume Control for built-in input/output devices. This setting will be remain enabled until you switch the "Reduce volume on open" check box off in the same pane.
Troubleshooting: If you cannot click the Built-In Input/Output section of the System Preferences window, you can try this procedure.
- Drag and drop the Speaker icon into the Menu bar, then right-click > Customize menu bar option as you can see on the screen in Fig3 above.
- Click the "Select New " button next to "Built-In Input/Output".
- Click menu item "Open Sound preference panel" under the General tab.
- Turn on the "Reduce volume on open" check box.
- Check the boxes below the "Reduce volume on open" check box as necessary.
- Click the close button of the System Preferences window.
However, this method is not so convenient as using menu bar items.
Volume Control is Fig4 for HDMI settings Affected OS and such devices as Mac OS X 10.6 Snow Leopard or newer, Mac Mini (mid-2011 models), MacBook Air (mid-2012 models), iMac (late 2012 models). Affected input/output device: HDMI. Affected audio output device: Built-in speakers and external audio devices that use built-in output features of Macs such as line out port etc. Moreover, you can try the Audio MIDI Setup tool to configure the sound balance.
Hope it was helpful for you!