Gas and Oil Home Heating Furnaces - One more Heil unit question.

I've received alot of help on this board and hopefully this is my last question for some time. My Heil 3.5 ton unit works great/cools very well. I have a concern about a noise that it seem to make as the day goes along. When the unit kicks on first thing in the morning it turns on quiet and smooth with little noise. As the day heats up (110 degrees) I have noticed that the unit, when it kicks on, will make a rough noise and then taper off but it is still louder than it is in the morning. When evening comes it starts rough and smooths out and sometimes you can hear a slight hiss noise but this is only after it has ran all day. Does it sound like the compressor is going out? It cools great and runs smooth when cold but makes noise as it heats up from use. Could the capacitor be bad and the compressor is having an initial hard start? How would I check that and would a hard start cap. make any difference? Thanks for the help.

Forgot to mention: The reason I inquired about the capacitor is because I live in a mobile home park and have noticed that when my neighbors unit kicks on sometimes my lights will dim for a brief second. I was wondering if this might affect the unit as far as current draw? Thanks again.

1) The sound of the compressor varies with the stress and effort that varies with its load and other factors. You worry overmuch about it.
2) The dimming of your lights when the neighbor's unit starts says nothing about your unit. The transformer supplying your power is under heavy load and the voltage drops when the neighbors unit comes on (thus the dimming). This is somewhat normal especially in the hottest weather. I wouldn't stress about it.

OK, thanks. I knew I was probably being paranoid but thought I would ask anyway since I have had some bad luck in the past regarding AC units. Thanks again for the ease of mind.