Comments to: Infrasounds in Residential Area – Case Study1

The article, published in the most recent issue of the Journal, presents measurements of low and infrasonic noise emitted from an industrial zone and transmitted into a residential area. The measurements seem to have been carried out with relevant equipment and care, and the results are very much in line with, what I believe can be found in many residential areas lying close to industrial zones. However, the authors have used G-weighted levels for evaluation of noise with significant energy in the range about 20 Hz, despite the fact that the Gcurve has a low frequency cut-off at 20 Hz. This misunderstanding leads to peculiar conclusions, and it calls for comments. The article may leave the reader with the impression that infrasound having G-weighted levels as low as 62-70 dB can be perceived by humans and give rise to complaints. This indication is far from the presently accepted threshold of perception of 90-100 dB(G), and it certainly cannot be concluded on basis of the observations reported. The authors also use unweighted levels, but filtered with a low pass filter at 20 Hz, and obviously this does not change the problem. The introduction of the article reports on "reasons for complaints ... of acoustical origin", and on problems relating to infrasound as being "of increasing importance". Measurements within the residential area show Gweighted levels of 62-70 dB, and levels of 57-66 dB, when measured linearly up to 20 Hz (lower limit not reported). The authors do not mention audibility explicitly, but state that these levels are "harmless to the human hearing organs". Taken the introduction into account, the reader may understand that the measured levels can be perceived by humans, but they do not damage the ear. The authors continue by claiming that the "... possibility of non-auditory effects of infrasound on the housing estate inhabitants cannot be definitely precluded ...". Well it cannot be precluded, but on the other hand, nothing in the study has suggested that infrasound should be the cause of the effects, and the statement would have been equally true, had the G-weighted levels been even lower. No effort was done to report more precisely on the non-auditory effects and to discuss their existence, nature and origin. Nevertheless, the connection to infrasound is suggested to the reader without the slightest foundation in the study. The authors seem unnecessarily concentrated on the infrasonic region. Their