Dumidifier whistles upon startup

I bought a Friedrich 40 pint dehumidifier. It makes a whistling noise for a
few seconds when the compressor starts up. The whistling noise does not
seem to happen if the unit wasn't run for a while. The noise sounds a
little bit like a tea kettle whistle and sometimes alternates between a
higher note and note that is maybe a major 3rd lower to a tritone lower.
The pattern is Higher Note LowerNote HigherNote then no whistling.
Sometimes it's more of a constant tone. Anyway the noise goes away after a
few seconds. Is this normal?

J.


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