Lockdown events

Bit late posting this.
Listened to a few of this years BBC proms broadcast from the Royal Albert Hall without an audience.
I was surprised at the level of background noise heard in the broadcasts.
Although I have heard similar before I guess I assumed the background noise was mostly from the audience (breathing, coughing, shuffling in seats).
Anyone else noticed?
 
Bodies in the seats absorb sound and don't reflect it well. An empty hall has different acoustics.

I was a touring sound man back when, and the sound at sound check was not the same as with a full house. For that matter, in a dance club, even first set and third set can sound different as the air fills with humidity and tobacco smoke.
 
I should have been more specific.
I was hearing what sounded like the hiss you hear from your speakers if your stereo is not up to scratch. Perhaps the mics and long cables in the hall were not so electrically silent. Maybe the HVAC was noisy.