/// John has the right idea. There are plugs on these engines that will whistle with a small air leak. Go to a hardware store and buy stiff polubutyl and fexible vinyl to make an earphone. Spray carb cleaner on manifold gaskets etc. to locate leaks.

If your belts are out of line from alternator mounting bushings being worn there may be a spray of worn belt material on the inner fender just even with the alternator pulley.

Do not use anything except belt dressing on "V" belts. It is available in spray cans. It will get you by for a few days if the problem is worn, slipping, belts. Test the alternator bearing by releasing the belt pressure at the alternator adjustment. The alternator will stop and the bearing cannot make noise stopped. Before releasing the alternator test the belt at the alternator by pushing on one of the alternator cooling fan fins (with the engine stopped). If you can turn the alternator by hand the belt is problably bad.