Every electrical device with a built-in compressor makes more or less noise. A portable AC is no different. Rather than the wall-mounted split or window AC, the indoor unit of a portable AC is installed away from the wall and closer to the user. This is why you may find it slightly noisy. Although, the intensity of noise depends upon the quality of the product. We have found that portable ACs from reputed brands make noise in between 50-54 dB.