If you're having trouble hearing the other participants in the Space, make sure to test your speakers/audio to make sure they're working correctly. To do this, you can do the following:
Test Speakers in the Space:
When in a Space, click Setup > Device Setup > Test Speakers. If you can hear a tune playing then your speakers are working just fine.
Test Speakers in the Lobby:
When joining a Space, test your speakers in the Lobby. Here's how: