Tammi,
You are describing metallic sounds I can't hear well.
Being a long time shooter that started long before hearing protection was talked about or suggested, I've got a lot of high pitch hearing loss. And that includes certain metallic noises. Low pitched noise I hear just fine ...
.
That's why I can't hear what you described, but I do hear the noise the flat spotted drive wheels cause.
I have several electric and motorized treadle long bobbin machines, both friction drive and belt drive. Their noise varies from mild to wild. And I've got one long bobbin treadle, my Franklin (uses Singer size shuttles and bobbins) and it's one of the noisiest.
Joe