A Question About the Adhan in Our Multi-Faith Space

As-salamu alaykum dear brothers and sisters, I have a small question that's been on my mind lately. I work at a university in a Western country where we're fortunate to have a multi-faith space for prayer. Although it's mainly used by Muslims, it's a great facility for us to perform our daily salat. My question isn't about the space itself, but rather about a practice I've noticed among some of our brothers. Before the iqama, some of them recite the Adhan inside the room. I've always understood the Adhan to be a call to salat, inviting people to come and pray. So, I was wondering, what's the purpose of reciting the Adhan when everyone in the room is already there to pray? I'm not suggesting we should make the call to salat publicly in the university; we must respect the laws and norms of the country we live in, just as mosques in Western countries do. My question is more about the validity of salat in relation to the Adhan. Is there a ruling that salat is not considered valid until the Adhan has been recited? I'd appreciate any clarification on this matter. Jazakum Allahu khayran.