Young children are not the only ones frightened by things that go bump in the night. Fully grown home owners often become terrified when they hear bumps, bangs or other noises emanating from their houses—that’s because these unfamiliar noises might mean steep home-repair bills. Although some house noises do indeed mean that it’s time to call in a pro, others point to simple problems that home owners can fix on their own…and certain sounds can be ignored entirely. Here’s what home owners need to know about 11 worry-inducing types of house sounds…

Heating and AC Noises

Heating and air-conditioning can make any number of noises…

Pings and dings from ducts and radiators are perfectly normal and can be safely ignored—they’re just metal expanding and contracting due to temperature changes.

High-pitched squeals or a grinding noise from a furnace or an air conditioner could mean that a moving part is not moving the way it should and requires quick action. Immediately shut off the system, then wait a few moments and turn it back on. (If the troubling sound is a whine, replace the unit’s filter before turning it back on—the restricted air flow caused by a dirty filter could be the cause.) If the sound returns, shut down the system again and leave it off until a heating, ventilation and air-conditioning (HVAC) professional can take a look unless temperatures are so extreme that you have no choice but to use it. The problem could be ­something simple such as a worn bearing or belt that an HVAC pro can replace for just $100 to $150.* But the longer you allow the unit to make the sound, the greater the odds that the small problem will cause a larger one as parts strain or overheat, and then a motor or pump may have to be replaced.

Frequent clicking sounds from a furnace or air conditioner often mean an electrical relay is malfunctioning. This, too, requires a call to an HVAC pro, but the repair bill shouldn’t be much greater than the basic service call rate, usually less than $100.

Electrical Humming

Humming or buzzing sounds from an outlet or switch usually mean that a wire has come loose. (Dimmer switches can hum for other reasons—see below.) If so, the switch or outlet might be warm to the touch as well—although not necessarily. A loose wire is a fire hazard, so call an electrician right away to check out the humming or buzzing. If it is just a loose wire, fixing it should cost no more than the basic service call rate, typically less than $100.

Humming or buzzing noises from a lighting fixture could point to a loose wire as well—but with lights, there’s a good chance that something else is to blame. If the humming light is on a dimmer switch (or the dimmer switch itself is humming), replace the bulb with a different type of bulb or one made by a different company. Some bulbs mention on their packaging that they are designed to work well with dimmers. If that doesn’t end the sound, replace the dimmer. If a fluorescent bulb is making the noise, the fixture’s “ballast” might need to be replaced (the ballast is the part of the fixture that controls voltage to the bulb).

Wall or Attic Sounds

Scratching or scurrying from within a wall or ceiling. You can probably guess what this means—a rodent (or some other small animal) has gotten into your house. Get it out as soon as possible. The longer this uninvited houseguest lingers, the greater the odds that it will chew through wiring…die in your walls, causing an unpleasant lingering odor…or give birth to babies.

A pest-control professional should be able to solve the problem for between $100 and $300 (potentially more with major infestations or in expensive ­areas). Or purchase and set traps—avoid poisons, which could be consumed by your pets or result in the pests dying and rotting inside your walls.

Do not just evict the pest—also search for and seal the opening that it used to get into your home so that other animals can’t get in. Expanding spray sealants are a simple and effective way to fill small gaps. One spot to check: If you have a crawl space under your house, look under tubs and showers—builders often fail to properly seal off the openings beneath drain assemblies.

Dripping. A water leak inside a wall can destroy wallboard and insulation and lead to mold or mildew problems. Fortunately, not every water sound signals a problem—sometimes the water is safely inside pipes.

First, check your basement or crawl space below the spot where you hear the water sound. If there is a water leak, that water likely would find its way down there. If you see water or water damage, call a plumber immediately (or a roofer if the water dripping sounds occur only when it is raining and/or when there is ice or snow on the roof). If you do not find water beneath the location of the dripping sound but the troubling water sound persists, conduct a water-loss test. Stop all water use in your home for 30 minutes—instruct family members to refrain from flushing the toilet and using the sink, tub, shower, dishwasher and washing machine during this time…and turn off the ice maker, sprinkler system and any other systems in the home that use water on their own.

Note the exact reading on your water meter at the beginning and end of this half hour. If this reading has not changed, it’s unlikely that you have a leaky pipe. If it has changed even slightly, shut off the water to your toilets and redo the test—leaky toilets are the most common source of phantom water use. If this second test still shows no water use, it would indicate a toilet is leaking. Check the overflow control in the toilet tank or consider replacing the toilet’s flapper valve or call a plumber.

Alternative: If you have a heating system that uses hot water or steam, the leak could be from there. Monitor the boiler’s pressure gauge—if the system is leaking, this is likely to show a loss of pressure over time.

If you have a well: You won’t have a water meter to check, so instead, stop all water use and then stand near your water pump for 30 minutes. If you hear clicking sounds from the pump, that could mean you have a water leak.

Banging or Thumping Pipes

This is called “water hammer” and is caused by water changing direction or being brought to a sudden halt in pipes. Water hammer almost never causes any problems for the home, but the noise can be annoying. If you want it to stop, install “water hammer arrestors” in the ­waterline near appliances and fixtures that tend to trigger the noise. These cost just $10 to $15 at home centers and provide a cushion of air that absorbs the force of the water, greatly reducing the noise. If you call in a plumber, it should not cost much more than $100 (you can save $85 by doing it yourself).

Water-Heater Noise

Water heaters fueled by natural gas or oil make a subtle “poof” noise when the gas or oil ignites at the start of a heating cycle. Other than that, water heaters should operate almost silently. If you hear gurgling or popping noises coming from your water heater, that means it’s struggling to operate and might soon fail, most likely because sediment has built up around its coils. You might be able to save the water heater by draining it to flush away this sediment. Check your heater’s manual for specific instructions, but typically the procedure involves shutting off the water and electricity to the water heater (even gas- and oil-fueled heaters use electricity for ignition), attaching a hose to its drain spigot near the base, running the other end of the hose to a drain, then opening the drain valve. After the water heater has drained, close the drain valve and turn on the electricity and water to the tank. Do this every year.

Well Pump Clicks

Occasional clicks from a well pump are normal—it just means that the pump is working. Frequent clicks when no water is being used in the house suggest that either an electrical relay in the pump is faulty or that there is a water leak in the house. Use the leak-check procedure described in the water-dripping section above. If that does not turn up a problem, call in a well professional to see if there’s a faulty relay switch. Replacing the switch shouldn’t cost more than $100. Don’t let this problem linger—until it is fixed, your well pump is under unnecessary strain, which could shorten its life.

Fireplace Dripping Sounds

If you hear dripping from your fireplace when it rains, it could mean that rain is finding its way down your chimney. You need to put a stop to this or the metal firebox inside your fireplace could rust, creating a fire risk. The source of the problem could be as simple as loose flashing or a dislodged chimney cap. If so, a roofer probably can correct it for less than $100. You even might be able to solve this yourself, perhaps using caulk to seal gaps between the flashing and the chimney if you are comfortable walking on your roof. If bricks are coming loose, you might need a brick mason, which could cost hundreds or thousands of dollars depending on what’s needed.

*All repair prices cited include parts and labor and are based on typical component and service rates. Prices may vary by region.