Why is an air conditioner so much louder than a fridge? Dont they function similar?

A Sledgehammer is a hand tool that is classified as a striking tool. They have a very heavy steel head that is available in a few weights. The handles are 36 inch's long and made from Hickory , which is an extremely hard wood or they can also be made from fiberglass. Those sledgehammers are used for pounding , or drilling spikes into the ground, and also breaking up things like concrete materials fro easier removal. Sledgehammers are usually purchased for small jobs and most DIY Homeowners projects. 
Jackhammers are a commercial pneumatic power tool that is owned mainly by city crews, road crews, plumbing business, and other companies that need to break up concrete and other material fast. They have a hydraulic drilling type action and a powerful pneumatic 
motor and can go through a piece of thick concrete, pavement, rock in a matter of moments. 
Jackhammers are usually never owned by Homeowners , only by companies.

Sledgehammer is a large metal hammer looking tool that is used by brute force (manual labor) most are 20 lbs with a long handle. 
While a jack hammer, Offers you several bits to use depending on what you need it for. The jack hammer uses electric for power or air power to run them. It requires the purchase of one or the other while the electric jack hammer is around $1400.00 The air jack hammer runs into the thousands. You can also rent them.

A sledge hammer is an oversized mallet basically. It has a long handle, and a heavy head, usually between 8 to 12 pounds. You have to swing it like a hammer to get work out of it. A jack hammer is a power tool. They can be either electric or pneumatic, the pneumatic ones being larger, more capable. Both are used for demolition work.

A sledge hammer is just a very larger version of your basic hammer for pounding with greater force... a jack hammer is a much heavier power tool powered by compressed air or an electric motor that does the pounding for you, can accomodate any number of tips, such as spade or pointed gad, in essence it's a huge heavy air chisel.

Definition of sledgehammer : a large heavy hammer that is wielded with both hands 
Definition of jackhammer : a pneumatically operated percussive rock-drilling tool usually held in the hands; 
a device in which a tool (as a chisel for breaking up pavements) is driven percussively by compressed air