There might have been a point when Ryan would've enjoyed the silence, embraced it. Silence is peaceful, uninterrupting. She could have gotten used to the entirety and absoluteness of space's quiet.
But— now Ryan can't stand the silence. Trapped in a cockpit and running out of oxygen, silence is the last thing she wants to hear. Silence is no longer peaceful. It's the calm before the storm, it's the thing that drives home how very alone she is, how Kowalski isn't there anymore. Silence is now the absence of hope. She's stranded outside the atmosphere with no hope of survival and she thinks she'll die in silence, at least.
But she lulls herself to sleep with the crackling, spit-out noise of the radio. She doesn't want to die alone, like her daughter, hopeless like Kowalski. And maybe— just maybe—silence won't be the last thing she knows.