The quietest air conditioners as of 2015 are generally manufactured by Friedrich, according to Noise Help. Consumer Reports also states that those machines are "whisper" quiet.
Consumer Reports state that Friedrich brand air conditioners are not only quiet but also energy efficient. Some of the models can also be turned on through a smartphone or tablet. However, Noise Help states that the unit is tricky to install. Installation also takes a long time as proper installation is crucial to reduce the amount of noise the unit makes. However, once installed, customers state that the unit performs well and looks stylish.