97 Honda Civic Hi-Pitch Sound When Moving in Reverse

I have a 1997 Honda Civic w/ about 150k miles on it. The belt was changed a little under 2 yrs ago. Just started making a high-pitched sound when backing up. Sounds like a note on a flute, and doesn’t sound like grinding. It only happens when backing up. As soon as I stop, shift and go forward the sound goes away. Began 2-days ago. I try to find parking spaces where I don’t have to back up.

Where is the sound coming from? Front of the car, rear, passenger side, driver side, can’t determine?

Thank-You for Responding … I think the sound is coming from the front. but cant be sure if drivers or passenger side.

Does the Civic have a manual transmission? If yes, check the oil level.And regardless of transmission check the engine mounts.

Wait, it’s a 1997 Civic, and it only has one belt? I am pretty sure the 6th generation Civic has many belts. Which one was changed?

Is this a CIVIC HX with the CVT transmission?

Let me explain where I was going with my first question. Since the sound is coming from the front, I suspect that you have a vacuum hose that has cracked right at the fitting. In neutral, lets say your engine is perfectly vertical, it isn’t but lets just say that it is for now. If you have an automatic transmission and you put it into gear, the engine rocks to one side. In theory, it should rock in the same direction, the same amount whether in drive or reverse. But for some reason, there is usually a difference between drive and reverse.

It may be that the engine is rocking just enough in reverse to tug on the vacuum lines and that tug might be enough to allow air into the crack. The passage of air through the crack will make it whistle.

Open the hood and have someone else put the car in reverse and see if you can locate the source of the sound. Check all the vacuum hoses in the vicinity of the sound by tugging on them just a little. If you tug on the right one, the sound will change.

I should have asked this, do you have to be moving to hear the sound and if so, does it change pitch with the speed?