How to redirect MacBook Pro audio to my TV?
Hold the Option key and click on the Volume/Sound icon on your Menu Bar. When you're connected via HDMI, you should have an option show in the local menu to select that connection to feed the audio through rather than the standard audio output.
If you've removed the Sound menu bar item, you can also change the output device through System Preferences → Sound → Output. There, you can change it by selecting it from the list.