There are many different reasons you might have noise in your air conditioner. You might also be hearing vibration between the glass and the frame or the sash and the frame. Most people will install window air conditioners. If yours is, you should have it looked at by an authorized service professional. 

Determine what you need your unit to do and then research online to find the best deal. 

You might have bent fan blades which would be causing your unit to make noise. The higher the decibel the louder the unit will be. Therefore, you will save on your energy costs. Therefore, a more energy efficient model will save you money in utility costs. Some cannot be helped. You don't want to overload your electrical system. If you keep the unit running, your utility bill will be higher. 

One drawback of window air conditioners is that they are noisy. If you are one of those without central air, you have to find some other way to cool your home. To stop some vibrating, look for the screws that hold the front panel to the unit and tighten them. The noise level depends on the type and size of the unit. Other causes could be maintenance issues such as worn bearings, dirty or rusty fan blades and basic wear and tear. The more features it has, like double fans or a remote control will increase the price. Air conditioner units can use a lot of electricity. For example 50 decibels is 10 times louder than 40 decibels and is 100 times louder than 30 decibels. 

A unit should not be unbearably noisy. Noise levels are usually given in decibel ratings. 

You can find lots of different types of air conditioners, along with lots of different prices. Make sure you check the amps for the unit you purchase. For every 10 decibel increase the sound pressure increases by a factor of 10. You should be able to find a window air conditioner for as little as $150 or as much as several hundred. It is fairly easy to bend the blades back in place. If you want to take your cool air with you from room to room, consider a portable air conditioning unit.

Most homes these days are built with central air conditioning. The compressor and fan which is in every unit causes most of the noise. You can do some basic maintenance yourself. 

Usually the more expensive the unit, the more energy efficient it is. Besides basic wear and tear, your unit could be noisy because it is vibrating because it is not installed correctly. If a unit is more efficient, then it will take less energy to cool your home. Make sure you've checked the simple things before you call in a professional.