My 72 chevelle is making an odd niose when im driving but is inconsistant. It almost sounds like a horn type noise. It only happens when i take my foot off the accelerator. Its pretty loud and almost seems to be coming from the drivers side engine compartment. I was told voltage regulatores make noise when going bad and i replaced that and its still doing it. Could it be the brake booster??

Horn relay? It's next to the brake booster. Try unplugging the black wire from the relay.