An update. My med supply place said that my machine has begun it's demise. From my research, it sounds like it might be worn out bearings or something. He is applying for a replacement from the insurance company. It has been 6 years in March and currently I have over 16,400 hours on it. He said the ...

I came back looking for an answer to the same question.

I'm getting what I would call a "high pitched harmonic" sound. Last night it was so bad that I put the machine on the floor under the bed.

In the past it's happened before but only for a moment or two and then went away.

Any ideas?