Wow, mine does too sometimes! Breathing and sighing noises. Like it's sniffing? Inhale and exhale... Really freaked me out, I thought some kind of large animal had chewed through the floorboards and was under the freezer! I looked all over and it isn't an animal, (i hope!!) but seems to be coming from inside the freezer compartment because it's louder with the door open. Maybe it's the defrost cycle or something?
if the unti working good and cooling then change the filter it may be too old.
With the limited information, it is hard tp properly diagnose... DR Horton typically installs one unit on a two story and has it control all zones which is not the most effective means of HVAC. Homes are typically calculated, designed and "balanced" with the household doors open in order to get an even, balanced temperature to withing 2 degrees F. Heat rises and cold air falls - in open floor plans with the upstairs thermostat on the 2nd floor exposed to the downstairs heat rising upwards, this can cause an unbalance. If more definitive info can be provided, more specific info can help narrow down the issue.
The # 5 thermistor , pt # WR55X10025, located at the bottom of the freezer , slightly in front of the drain , with 2 white wires going to it , slid into a housing . This thermistor , is the freezer thermistor , which tells the control board , the freezer temp , when to cycle off , and is associated with the fan speed . The " breathing " sounds like the fan speeding up and slowing down . Replaceing this thermistor , should fix the problem .
As the previous poster said, it's probably a problem with your water.
Are you using tap water or bottled mineral water? If so, there are minerals which get nebulized along with the water, and leaves a white, dusty, residue. I fill my Crane Pig humidifier with DISTILLED water, which is pretty pure. Make sure that the water is DISTILLED ONLY, since some of the water companies distill the water and then add minerals back in (they almost got me here until I noticed the label that said "with minerals added"). The reason this is important is because during the distilling process, the water is boiled, evaporated, and then the vapor is condensed back to liquid. This removes any impurities or dissolved minerals from the water. You can see Wikipedia for more on this topic here.
Additionally, I use both the Crane Demineralization Filter Cartridge (which works for the penguin as well, and gets installed in place of the original water tank cap), and the ProTec PC-1 Humidifier Tank Cleaning Cartridge (which I plop into the water tank) to keep the water both de-mineralized and bacteria free. I got both products at Amazon.com.
With these 3 things, so far I haven't had any white dust residue, and the mist feels fresh and clean.
On a side note, by using distilled water, you also prevent any mineralization from building up on the nebulizer or water level sensor, which can cause the humidifier to eventually stop producing mist...