The Mechanism of Impact Noise and Hard Floors

In 2005 the Department for Environment, Food and Rural Affairs (DEFRA) commissioned Napier University to carry out a study on the noise implications of laminate and hardwood floor surfaces. This study covered many areas and will likely be referred to more than once on this blog.

Quite often it appears that the noise generated by laminate flooring is misunderstood or denied by both the owners of the flooring and the various authorities receiving complaints. The DEFRA study contains a fantastic diagram showing the sound transmission mechanisms of footfall noise. It should be noted, however, that footfall noise is not the only source of impact noise travelling through and across laminate floors. Impact noise is also caused by running and jumping, doors and cupboards closing, drawers opening and closing, light switches, plugs in sockets, vacuum cleaners, sweeping brushes, washing machine vibrations, furniture being moved, items being thrown, bounced or dropped and noise from pets.

As demonstrated by the diagram, there are three mechanisms of noise transmission that act upon the room below. Forced transmission occurs at the point of impact and directly transmits the impact noise through the floor into the dwelling below. Flanking transmission also occurs, best described as the impact noise travelling across the laminate flooring and transmitting sound to the adjacent walls - this noise will also travel to the rooms below. Finally, specific low frequency transmission occurs when the forced motion causes the floor to deflect and compress the air in the lower room changing the air pressure at the eardrum.

The DEFRA study suggests that impact noise "typically occurs within the range of frequencies between 40Hz to 2500Hz, although with a dominance at the 63Hz to 250Hz low frequencies." The study also showed that the installation of laminate or hardwood surfaces can increase noise transmission by up to 21decibels compared with traditional carpeting.

Whilst the main body of complaints are generated from dwellings underneath laminate flooring, there are a number of complaints from residents in adjacent flatted, terraced and semi-detached housing.