The compressor is also a source of noise by transmitting its rotational vibration to the cabinet and through the copper tubing. If metal cabinets are used they can even amplify low frequency vibration creating a drumming or beat frequency. Heat Siphon's compressors are mounted using special rubber isolation feet to elmininate vibration transmision.
Heat Siphon's thick solid PVC vacuum-formed cabinet further reduces sound levels and absorbs any higher frequency noise instead of amplifying it.