Endmill sounded loud with a bit of chatter

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Hi all. I’m using an amana 7/32 upcut 1/4 shank endmill. Cutting slots at .125 doc, 80ipm and 18000 rpm. cutter sounded loud with a little bit of chatter. I was cutting black walnut 1" thick all the way thru. could it be speeds, feeds or just the way it is. thanks