Centre speaker high frequency issues?

[Daniel Weston]

So I've noticed recently that my Polk centre isn't handling a specific sound very well. It only happens during sporting events and when for example, a wicket is taken in cricket or a goal scored in a footie match, the noise of the crowd celebrating sounds as though its distorting.
The speaker sounds fine to me during any other playback situations.
Is there a plausible reason for the distortion I'm hearing?
Cheers
Daniel

 

[scrarfussi]

 

[Daniel Weston]

 

[scrarfussi]

 

[chrisc]

 

[windshear]