If you walk past a group of guys and they go quiet, were they checking you out?

I walked past a group of about 6 guys my age (whom I didn't know) and they went noticeably quiet as I passed. I'm not thinking it's normal for a group of 6 boys to go quiet, so, were they checking me out?
If you walk past a group of guys and they go quiet, were they checking you out?
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