Most modern 1.5 ton split ACs make 34 to 46 dB of noise within the tolerable limit. Yet sometimes, you may hear a weird buzzing noise in the AC, which can signify some problem. It can mean anything from a malfunctioning compressor to a broken part. The noises can also be heard if there has been a refrigerant leak. So, anytime you hear such a noise, you should call a professional who can help get rid of the problem.