Low Frequency Noise

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."