A sharp bang in the pipes right after a tap, washer, or ice maker shuts off is usually water hammer. It is a pressure shock, not a loose pipe. You can test for it yourself before you call anyone to tighten a fitting that may not be the cause.
What each problem sounds like
Water hammer is a single hard knock that follows a valve closing quickly. It often comes from the same spot each time, such as the wall behind the laundry or the kitchen. A loose pipe more often rattles as water moves through it, and it may shift when you push it by hand. Pay attention to when the sound happens, because timing is the main clue.
Check when it happens
Run the hot tap fully, then close it quickly. Note whether the knock appears. Repeat with the cold tap. Then run the washer or dishwasher through a fill and watch whether the knock follows the water valve closing. If the sound follows only one appliance, the valve and the supply line to that appliance are the first places to look.
Check the pressure
Hammer gets worse with high static pressure. Look for a gauge on a hose bib or a test point, and read the static pressure with no water running. Ask whoever services the water system where the regulator is set and whether a shock arrestor or air chamber is installed. A missing air chamber, or one that has lost its air, lets the shock travel through the pipes.
Check the pipe
With the water off and the line drained, push each exposed pipe by hand near its strap. Look for movement, wear marks at the strap, or a pipe resting against framing. Secure any loose run with a proper strap and cushion. Do not strike the pipe to test it.
When to stop and call
If the knock comes with a wet joint, a drip, a stain on a ceiling, or a fitting that weeps, stop the test and call a plumber. A wet joint is a separate question from a noise, and it needs someone on site to look at it.