Airborne sound insulation

Standard Test Methodfor Measurement of Airborne Sound Insulation in Buildings, ASTM E336-90, ASTM, Philadelphia, Pa., 1990. 

Linnecessary noise, these should be cleaned regularly. Imbalance, whether due to dirt or to other causes, should be corrected by adjustment. Detective bearings should be adjusted or replaced. Struts and sharp edges in front of an impeller should be avoided. Impact noise insulation should be introduced between fan room and floor structure and between fan room and connecting ducts. The fan unit should be enclosed, with satisfactory airborne sound insulation as the objective. 

ISO 717-1 2013, 2013. Acoustics—Rating of sound insnlation in buildings and of building elements—Part 1 Airborne sound insulation. International Organization for Standardization. 

By using polymers, proper sound insulation can be achieved easily and effectively. Cellular plastic materials (with open celled flexible structures) are shown to be very effective in sound insulation (either for impact noise from footsteps and movement on the top floors of a building, which can usually be eliminated by floor insulation, or airborne noise, which is from noises in the neighbourhood or the street, and which needs wall/party wall insulation for its elimination). Open cell flexible cellular plastic materials also provide acoustic insulation at high frequencies. 

Improvements in primary acoustic performance, in terms of dampening of airborne and structure-borne sound, can be credited mainly to polyurethane. Flexible PUR foams are used for the insulation of the engine bulkhead, the floor pan, the roof, and the doors. Normally the flexible foam will be sandwiched between the structural panel and a massback , in the form of a heavy mineral-filled layer of PVC or polyolefin. Recent models, following the Fiat Tempra, feature PUR foam injected into the hollow sections of the body structure and the instrument panel. 

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