Humming from intake

I have an 89 sc auto. Just last week the intake started making a noise like a horn going off on a dead battery. This gets louder as I drive but only when I let off the gas pedal. I have checked for leaks and have found none. When it started, I pulled over and pulled off the intake filter. Noise was then amplified x2, but once I put the filter back on it stopped for a minute or so. From time to time my battery also is dead the next morning. I have replaced it twice.

Do a search regarding the idle air control valve. I've never had this go out on me, but I've read that when the idle air control valve goes out, it sounds like a dying goose in the intake.

Regarding your having to replace 2 batteries. that sucks. maybe the alternator is bad? Autozone tests them for free...

Just fixed the same thing on mine for less than $70.00, do a search for the threads on IAC. If the IAC is your howling goose sound problem it is an easy fix, 2 small bolts, 1 wiring plug. The battery problem is unrelated to the IAC problem.