@ikluEnsure that the audio device that you plan to use is connected to your computer well before you start up 0ad, as 0ad doesn't seem to be able to pivot to a different audio output device at runtime. Also, ensure that you have the correct audio device configured as the default output device in playback devices before starting 0ad.
Are you using HDMI audio output? 0ad may have a bug with HDMI audio output. Consider helping us resolve the bug by testing hotfixes. It would be necessary to setup a build environment and test patches. Or, consider using a different audio output device.
If it's still not resolved then see the FAQ answer to the question "No sound, no audio, or 0 A.D. is the only app with sound".