Most heating systems make some noise and this is normal;

Different types of heating systems make different noises. A steam system may make some of the same noises a hot water system will make, but both systems have unique sounds as well. Hot water base board. if installed poorly or if the fins on the elements are damaged, will make all kinds of noise, from pinging (this is caused by the fins of the elements) to a rubbing sound to a knocking sound or a tapping sound. and there is also an echoing sound that happens at random periods of time, noticeable mostly at night when you are trying to sleep.

 
The pinging
The pinging in baseboard heat is the metal fins on the element inside the baseboard covers. If the fins are bent or pushed together they will make noise when the heat comes on, because the copper pipe the fins are attached to expand when they get hot causing the fins to rub against each other, other causes for the pinging in the baseboard are, there is a guide that goes between the fins and where the element rests on the baseboard track, if this guide is not there the fins will make noise because they are rubbing against the baseboard track. Sometimes if the holes for the copper pipe going to the baseboard elements does not line up perfectly, an inexperienced plumber will push the element tight against the back of the baseboard to make the connection, causing the fins to rub against the back of the baseboard, also they may pull it forward to make the connection and have to force the front cover on causing the fins to rub against the front cover. This is nothing more then an annoyance, and is not dangerous.

How to fix this problem, remove all the covers and straighten out the fins, place something like wax paper between any places the fins are touching other parts of the baseboard, The pipes never get hot enough to cause a fire. Rubbing, tapping and knocking sounds are mostly all cause by the same thing, it just depends on how tight the pipe is rubbing against things. There are also banging noises, some people consider knocking noise to be banging noise, But for this page I will use the term banging noise to describe problems found at the boiler not in the walls of the house. First let me explain what happens when the boiler calls for heat. once the boilers starts to move the water inside the baseboard, it brings the colder water to the boiler to be reheated and at the same time sends very hot 180 degree F or hotter water into the pipes leading to the baseboard and into the baseboard and then back to the boiler again.

Copper pipe expands allot when heated, I think it's 1 full inch for 100 feet of pipe, it is the expansion of the pipe that causes all the noise. This is why, most inexperienced plumbers don't make preparations for the expansion and also don't sleeve the pipe properly, other big mistakes are, when drilling holes to run the copper pipe from one baseboard to another, the holes don't line up perfectly and the pipe is forced in causing the pipe to be pushed tightly against the floor joists. No insulators installed, this causes the pipe to rub against the floor joists even if there in no pressure from being pinched, Strapping the heat pipes tight against the bottom of the floor joists will cause noise because the pipe will move no matter how tight it is.

To solve this problem, install insulators or use the wax paper or tar paper at every place the pipe touches wood or other materials loosen all straps and wrap pipe with tar or wax paper and don't make the straps tight.

Banging noise

Banging noises found at the boiler are 1 big bang followed by a number of less load bangs, like an echo. This noise is caused by a combination of air in the system, a possibly defective expansion tank and a fast closing zone valve. It's important to note: it may not have anything to do with the expansion tank, I say this because so many people have the expansion tank replaced and find they still have the problem. This is what is causing the banging noise, One of the zone valves closes while the circulator is still running, the fast closing zone valve slams bouncing pressure against the expansion tank or air in the system, the pressure bounces back pushing the zone valve open a little and it repeats this a few times causing the echo banging sound. The most common fast opening and fast closing zone valves are Honeywell, Erie, The small White Rogers, Slow opening and slow closing zone valves are the Taco and the large White Rogers zone valves. I prefer the Taco zone valves over all the rest, except for use on any indirect water heater, Taco zone valves open too slow for indirect water heaters. It is not best to use zone valves on indirect water heaters, because zone valves can get stuck open causing the indirect water heater to be over stressed and can void the warranty, A separate circulator is recommended.

 
Hot to solve this problem. First thing to do is get the air out off your system then check to make sure your expansion tank is in good working order. You can remove 1 spring from the inside of the zone valve, this will cause the zone valve to close a little slower, or replace the fast closing zone valve with a Taco zone valve.

Sounds like someone is hitting the pipes with a hammer. On a hot water boiler, this sound can be very dangerous, check the temperature gauge if it is above 220 degrees F. shut the boiler down and call a heating Professional ASAP.

It sounds like I am sleeping by a brook or you can here the water flowing through the heat pipes. This is simple you have air in your system.

How to solve this problem, remove the air from your heating system