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than a 3 dB reduction in low-frequency noise to date. There is obvious low-frequency vibration at take-off and landing, caused by low-altitude turbulence and/or contact with the runway. But inaudible air pressure waves or vibrations are here suggested to be present (constantly or intermittently) at cruising speed and altitude, and generated primarily from the engines. than a 3 dB reduction in low-frequency noise to date. There is According to acoustic engineer Sean Moch, who has worke obvious low-frequency vibration at take-off and landing, caused with the Royal Air Force on a contract basis: "There has been a by low-altitude turbulence and/or contact with the runway. But large amount of work on effects of infrasound done by the MoD inaudible air pressure waves or vibrations are here suggested to in the UK, especially with regard to ground-operating personne be present (constantly or intermittently) at cruising speed and in the RAF who have to work near afterburning aircraft which altitude, and generated primarily from the engines. ave a phenomenal amount of infrasound. I have seen lead suits for aircrew which didn't look very comfortable" (personal com- RESEARCH RECOMMENDATIONS munication, 2001). In light of the information presented here, an extensive survey We may ask: if the RAF requires its aircrew to be protecte of infrasound in passenger jet planes is the obvious thing to do y lead suits, what is the risk for commercial jet plane crew an next, as a low-cost priority. Measurements should be taken over assengers, even without afterburners? the entire flight of various models (and ages) of passenger jet Commercial aircraft are lined with soundproofing material, planes, including at take-off and landing. Professional infra- evidently effective against entry of acoustic noise frequencies sound meters are now commercially available and these, togeth- from the engines. But such materials cannot prevent the entry of er with laptop computers, are all that is required. lower-frequency, longer-wavelength noise, especially inaudible These measurements should be unweighted, given that at 25 infrasound. Jet engines of commercial aircraft are already cov- Hz the dB(A) weighting required by existing noise legislation ered with lead or lead composite shielding to limit low-frequen- underrates the acoustic energy at this frequency by approximate- _cy noise transmission. The logical next step of lining the pas- di h i this fi b i i issi The logical f lining th ly 43 dB, or more than 99 per cent. At infrasonic frequencies senger cabin with lead shielding has obvious limitations in an below 20 Hz, the dB(A) weighting aircraft. required by existing legislation can It is known that some new result in an indication of much less metal-impregnated materials than one per cent of the actual have been designed to absorb energy present! infrasound; a team at the It seems that many people are University of Hong Kong has not aware of this fact as it applies Human body resonance . done such work. Lead or lead to sound and infrasound level has been proposed to explain Fomposite acoustic shieicing ms measurement: the situation has 4 een used around jet engines for arisen due to the erroneous belief the potentially lethal effect of many years—but you cannot aro ese enn et | igh-amplitude infrasound ff steiner orthe stan has been tailored exactly to its when used as a weapon. The US Office of Naval acoustic response. However, the Research (an aviation centre) at response of the human ear is but a Pensacola, Florida, is developing small window into the total range acoustic materials to attenuate of acoustic energies. low-frequency noise. In fact, they have managed a 30 dB INFRASOUND WEAPONRY attenuation at 80 Hz (pers. AND DEFENCE comm., Alves-Pereira, 2002). It is not known if this material is Human body resonance has been proposed to explain the suitable for use in aircraft or if it is effective against infrasound, potentially lethal effect of high-amplitude infrasound when used __ which by definition is below 20 Hz. a nn Tn Cmith's ax ao has been proposed to explain the potentially lethal effect of high-amplitude infrasound when used as a weapon. INFRASOUND WEAPONRY AND DEFENCE Human body resonance has been proposed to explain the potentially lethal effect of high-amplitude infrasound when used as a weapon. In Smith's work we have a strong indication that infrasound is potentially lethal, if this were needed in a situation where at least one US manufacturer (American Technology Corporation in association with Bath Iron Works) has announced (as at April 10, 2002) a contract for an acoustic weapon. Some years ago, an article in New Scientist magazine described the modus operandi of an acoustic crowd-control device as initiating epileptic fits in members of the crowd. This is consistent with VAD findings and with other evidence. It may be that some information on adverse health effects of exposure to infrasound is presently classified. Shurygin et al. (1975) have evidently investigated a specific effect of vibration and noise on military matériel squads of the Russian Army. Petrovic (1981) apparently investigated infra- sound and ultrasound in vehicles of the Yugoslav Army. Smith (2002) evidently worked with US aircraft and personnel. The Russian Army is apparently researching adverse health effects of exposure to overpressure from artillery (Belov, 2000). The Australian Army now has an interest in adverse occupation- al health effects of low-frequency noise or overpressure expo- sure (personal. communication with Lt Colonel Nick Rowntree, 2002). INFRASOUND IN OTHER TRANSPORT MODES Submarines are also large acoustic chambers as are surface ships enclosing various large chambers. Railway trains and buses also consist of large acoustic chambers, and with windows open would generate an infrasonic Helmholtz chamber resonance of significant amplitude. Inhabitants of buildings near to railway lines are said to feel upper body vibration when a train passes. In some metropolitan buses, the large side trim panels flap visibly at a low frequency, especially when the engine is labouring in "Drive" while stopped at a traffic light. Travel on these buses has typically led to an epileptic fit in one susceptible individual (pers. comm. with carer/healer Dawn Morgan, 2002). In motor cars, there is a "buffeting" effect at speed with a window open; and infrasound at a level of 90 dB has been measured in a car at cruising speed with windows closed (pers. comm., Alves-Pereira, 2002). The Royal Automobile Club of the UK announced in August 2002 that some drivers are susceptible to DVT syndrome, in particular those already at higher risk due to age, pregnancy, etc., and those driving for more than four hours at a stretch. NEXUS + 37 Human body resonance DECEMBER 2002 — JANUARY 2003 www.nexusmagazine.com