What causes high-pitched wheel noise at some high speeds?

On the Northeast Corridor and on the 150 mph zone in Rhode Island, sometimes when at high speeds (seemingly over 100 mph or maybe more), I can hear a high pitched whirring noise, and sometimes the pitch goes up. I assume that it’s due to metal wheel contact against a metal rail, and speed causes it, but what specifically causes it? It even happens on straight track.

Thanks.

If you were in the car closest to the front power unit, you could be hearing anything from traction motor 'whine' to transformer and/or motor cooling fan 'whine', or even regenerative braking motor sounds (electrically powered locomotives 'dymamic brakes' generate electricity back INTO the wire!)

I'm also inclined to say 'singing trolley wire' sounds are being heard. Back in the days of interurbans traveling 40+ mph in rural areas, one could easily hear the 'singing' of the trolley wire from the slider shoe on the trolley pole pressed against the wire as the car moves along. You'll still hear it at any operating trolley museum these days. Think of a violin string being played by a bow. So it's quite possible the pantograph is causing the catenary to 'sing' as well.

Or....

In the first years of Superliner equipment ('79-80 delivered), I had occasion to be in the handicap bedroom as that was the last roomette available. My room was filled the entire trip from Oakland to Chicago with a 'hollow sounding' whine that would change pitch with speed. The rear wall of the handicap room (and family room, too) was nothing but a single sheet of metal between me and the wheels. 3 years ago, I had to make reservation changes a week before travel and ended up in the family room. It was obvious that Amtrak and/or Pullman added sound insulating material on those walls.

For what it's worth, the same hollow 'whine' sounds were clearly heard in the 'Heritage fleet' equipment if you were in roomettes 7-10 and held the toilet pedal down and watched the ties whiz by underneath. The public toilet at the other end of a 10-6 was directly above the trucks, too.

Could it be the tilt mechanism? I know it's active below 100mph, but could something be different for it at higher speeds?

Thanks. This seems to happen in all train cars no matter where they are in the train.

Maybe “whirring” isn’t the right word. Maybe the noise is like sharpening a knife? It’s metal contacting metal and it happens at high speeds. It’s a lower pitched noise at moderately fast speeds and a higher pitched noise at higher speeds.

Could easily be wheel-on-rail noise, yes. Is it intermittent and associated with a side-to-side vibration? That’s probably hunting, where the rail gauge is slightly too wide for the wheels (4’ 8 1/4” perhaps.) If it’s constant, it might be that the gauge is slightly too narrow (like 4’ 7 3/4”) and the train is riding up on the wheel flanges instead of the flats.

The same issue could be in the wheel spacing on the axle or a bad wheel or rail profile. For that matter, it could be disc-on-brake pad noise. Wire singing is probably not going to present as a scraping noise, since the copper wire rides on a graphite carbon contact bar and shouldn’t be grinding on anything.