As detailed in the previous entry, "impact noise typically occurs within the range of frequencies between 40Hz to 2500Hz, although with a dominance at the 63Hz to 250Hz low frequencies." (DEFRA study on noise and laminate flooring - Napier University).
Another DEFRA research project, carried out by Salford University, investigates the effects of low frequency noise. Part of the research involved creating a Procedure for the assessment of low frequency noise complaints,and suggests the proposed reference curve of Low Frequency Noise as falling between 10Hz and 160Hz.
Correlating both pieces of information suggests that one feature of the impact noise generated by laminate flooring is that some of the sounds are Low Frequency Noise. This is borne out by Hood and Leventhall, 1971; Leventhall, 1988 ~ "Structure noise, originating in vibration, is also of low frequency, as is neighbour noise heard through a wall, since the wall blocks higher frequencies more than it blocks lower frequencies."
The Salford University article also notes fluctuating sounds are known to be more disturbing than steady sounds by an equivalent of about 5dB ~ this is also relevant to the nature of laminate flooring noises since they are not constant sounds.
The document also has this to say about evaluating LFN (Low Frequency Noise):
"Low Frequency Noise cannot be reliably evaluated on the basis of the investigator’s experience; indeed, officers investigating a case of Low Frequency Noise may not even be able to hear the LFN themselves. This is possible because disturbance by Low Frequency Noise is known to occur at levels only slightly higher than hearing threshold, which varies from one individual to the next. Also, the rate of growth of perceived loudness with level is more rapid at low frequencies so that a sound could appear loud to one person whilst still inaudible to another. An additional factor is that ‘sensitisation’ to low frequency sound appears to occur over time, and therefore a brief visit may not give an accurate impression of what it is like to live with the sound."
Tuesday, 29 April 2008
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.
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.
About This Blog
The purpose of this blog is to collect, collate, analyse and compare information regarding laminate flooring and noise. The blog is also focused with the health effects of exposure to noise. The focus will be on facts, studies, links, information and resources.
Personal accounts will be welcomed either in comments sections, or published as stand alone posts depending on the wishes of the poster. Personal accounts will be deleted if they contain inflammatory language, insults or information referring personally to people who own laminate flooring as this does not fall within the scope of this blog.
Personal accounts will be welcomed either in comments sections, or published as stand alone posts depending on the wishes of the poster. Personal accounts will be deleted if they contain inflammatory language, insults or information referring personally to people who own laminate flooring as this does not fall within the scope of this blog.
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