SFFrequentFlyer;
The noise was likely the brakes which can squeal and howl depending upon wear and temperature. The rattle could be the oleo movement over rougher areas of the taxiway/ramp area - also, brake shuttle valves (various purposes), on some installations make quite a strong clanking noise.
There is a hydraulic pump in the A320 which makes a quick buzzing sound during single engine taxiing. It's pressurizing one of the two engine-driven hydraulic systems while that system's pump is not turning, (engine shut down during taxi to save fuel). A high-pitched whine/buzz is a hydraulic pump which pressurizes the hydraulics for the cargo doors.
Crews would take every comment made into consideration but most comments arise out of unfamiliarity with the aircraft and crews usually don't have a spare moment on the ground to explain the details. They might pass the comments on to maintenance to have a look. Doesn't mean comments shouldn't be made but don't expect the undivided attention of crews - domestic flying has really short turn-around times and often a crew is out the door quickly, sometimes before the passengers to get to their next aircraft. It's just the way it is and it works well. All the same, thanks for paying attention.
Tell me something as an aside - it you're heading to or from a sun-destination, are you in sandles and shorts if arriving or departing a place like Denver in the winter? Not being a smart-axx here but I've seen passengers wearing t-shirts, shorts and thongs (the kind that go on feet...) all excited of course but an evacuation like we've just seen with such unpreparedness can really add to injuries and hypothermia. Just curious - used to see it all the time and wondered if most know that they're in an airplane in winter... ;-)