I can't hear sound when I connect my mac to a projector

Hello Yassora,

Thank you for reaching out to Apple Support Communities.

These steps may be helpful:

"If you’re trying to listen through external speakers

• Make sure the speakers are plugged into the audio output port on your Mac or display, and if necessary, into a power supply. Check for a power switch and volume adjustment on your external speakers. If necessary, turn the speakers on and adjust the speaker volume.
• On your Mac, choose Apple menu  > System Preferences, click Sound , then click Output. If your Mac has only one audio port, click the “Use audio port for” pop-up menu, choose Sound Output, then make sure your external speakers are selected.
• If you’re trying to listen through speakers or headphones connected only to the USB port on your Mac or display, choose Apple menu > System Preferences, click Sound, then click Output. Make sure the external USB speakers are selected. Open System Information, click USB in the Hardware section of the sidebar, then make sure your speakers are listed. If they aren’t, try unplugging the speakers and then plugging them in again.
• If your external speakers still aren’t working, check the instructions that came with your speakers."

More details can be found here: If you can’t hear sound from your Mac speakers

If the issue persists, can you provide a few more details? Does this happen in any other user accounts? Are you able to connect any other speakers and test? Also, what is your exact macOS version?

Cheers!