Hello, Huelvabulto. Thank you for posting your question to the Apple Support Communities.
We understand your situation and how you are unable to hear audio from a specific website when using your Mac. We’re happy to help you research any possible solutions to find a fix for this.
Since the issue is isolated to a single website, we’d first suggest that you clear the history and website data in Safari. The following Apple Support articles will help explain how you can complete these steps:
Clear your browsing history in Safari on Mac - Apple Support
Manage cookies and website data in Safari on Mac - Apple Support
Please let us know if you are able hear audio normally again from this website after completing these steps.
Cheers!