An air conditioner or heat pump sitting next to your house can create a lot of noise both inside and outside your home. To compare sound levels of different brands, ask your dealer about the bel rating of units you are considering. Bels, similar to decibels, range from 0 to 13. Most air conditioners and heat pumps operate at 8 to 9 bels; some units’ ratings are as low as 6.8. That may not sound like a wide range, but consider this: 9 bels sounds 10 times louder than 8 bels. That means one 9-bel air conditioner is as loud as 10 units rated at 8 bels. So we think taking the time to compare bel ratings is pretty sound advice. Sound levels inside your home may also be reduced by matching your outdoor unit with a variable-capacity furnace or fan coil.

There isn’t a standard sound rating system for furnaces, so it’s difficult to compare models.

However, models that have two-speed or variable-speed operation typically also offer lower operating sound levels, because there is less noise from the blower motor and from air turbulence at lower speeds. Carrier’s variable-capacity models even have a "ramp-up" feature that gradually introduces warm air into your ducts, helping prevent the "creaking" noises that come from ducts expanding and contracting.

Since two-speed and variable-capacity models normally run on "low" speed up to 90% of the time, you’ll find they’re a sound solution when you want to enjoy peace and quiet.