Which means itâs the lowest decibel level achieved from the quietest size within each model group during low fan-speed operation. Finding the quietest air conditioners Currently, the 50-60 dB range is as quiet as an air conditioner can get. 1  As of 2015, some of the quietest ACs include: 2  Carrier Infinity 19VS - 56 dB. 3  Dave Lennox Collection XC25 - 59 dB. 4  American Standard Platinum ZV - 55 dB.