Case studies of multiple clustered air-conditioning condenser units (ACCU) noise and vibration causing disturbance in multi-floor residential apartments compare airborne noise and structure borne vibration transmissions. "Split" A/C systems couple outdoor refrigerant compressor and condenser fan units (ACCUs) with indoor fan-coil units (FCUs). Airborne noise transmits indoors through windows, walls and roofs. Structure borne vibration from roof-mounted equipment transmits through roof framing and ceiling. Vibration transmission from on-ground mountings is normally insignificant. Compressor noise is loud, tonal and low-frequency dominant. Condenser (propeller fan) noise is broadband and loud. Case 1: Airborne (only) sound transmission from ACCUs on ground to an apartment building with measured sound spectrum levels near ACCUs and within receiver apartments. Case 2: Airborne sound and structure borne vibration measured near roof-mounted ACCUs and in receiver apartment below. Criteria for permissible continuous noise in residential spaces will be presented, and the relationship between surface-radiated vibration and audible noise will be discussed. Variations in disturbances between sources located on-ground versus rooftop will be discussed and compared. Sound and vibration spectrum charts will be presented for both cases. Concepts for vibration isolation, building noise reduction and interior surface treatments will be provided with subjective success, based on client satisfaction.
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