Thanks to the posts in here, I popped SH1 into my PS3 yesterday to see about that glitch. I haven't had my PS3 that long and so hadn't played SH1 on it yet. At first, I thought mine didn't have the glitch because when I shot the gun after first getting it, nothing happened. But then when I shot it at the air screamer, that awful, lasting sound came. I continued testing it for several minutes, and it only happened when firing at a monster, not just firing randomly. Maybe the radio static has to be going off for it to happen, or... I don't know.

It can happen inside or outside, and lasts until I leave the area. The sound stops when I pause the game, but continues when unpaused.
This isn't acceptable to me. Not only is the sound extremely loud and obnoxious, covering up other sounds and ruining the atmosphere, but I am not willing to play Silent Hill rushing through each area that I shoot an enemy in to get away from the sound.
I even made sure I got a used, completely backwards compatible model of PS3. (They stopped putting out the completely backwards compatible ones.)
Not only is SH1 an important game to me, but I now worry what other new glitches will pop up when playing other old games. A local store that sells mostly used things is having a sale next weekend, and PS2s will be cheap. I plan to get the 'fat' model of PS2, not only because it's listed as $40, about $10 cheaper than the slim one, but also because that's the model I had until I damaged it not long ago, then scrounged to buy my PS3...
Sigh.