So far, at least three gunners involved in Operation Vijay along the Line of Control (LoC) have been evacuated to the Western Command Hospital, Chandimandir, to recuperate from the after-effects of continuous artillery firing.

While one of the troopers has reportedly suffered ruptured eardrums, the others have complained of whistling in the ears or bleeding. Sources say some more cases may have arrived at other military hospitals.

``In addition to the high level of noise created when arillery guns fire, a high degree of air pressure in the weapon's immediate vicinity is also generated,'' an artillery officer commented. This, say doctors, has a direct impact on the eardrums. Thehearing ability of gunners, tankmen and signallers is known to deteriorate over the years.

``Loss of hearing also depends on the ears' internal condition and troopers' acclimatisation'', an Army Medical Cops officer commented. ``Also factors like distance from the weapon, the direction in which a soldier is facing or whether he has his mouth open or closed, have to be taken into account,'' he added. For instance, a trooper looking away from a gun is likely to have a lesser impact than one facing it, while anyone suffering from an ear infection or medical problem is more prone to suffer hearing deterioration. Also, if a person has his mouth open, it balances the shock waves and he is likely to suffer less damage.

Though there are no readily available statistics, sources estimate that 1 to 2 per cent of all patients visiting ENT departments, including dependants and ex-Servicemen, are cases where hearing loss is attributed to gunfire or exposure to constant noise.

The noise level exceeds 125 decibels whenan artillery round is fired. The normal noise level in a city like Chandigarh is 52 decibels, while normal human voice at a distance of two metres is less than 30 decibels. Experts say the intensity of sound doubles with every three decibels increase in noise level. This means that gunners are exposed to 24 times more intense sound than one is normally exposed to in a city. As per international standards, noise levels above 55 decibels are considered to be harmful.

Initially, there is a temporary shift in the hearing ability, which rectifies in a month or two. ``However, if exposure is prolonged, the damage is permanent,'' an Army doctor commented. With permanent damage, depending on the extent of disability, affected troops have to be placed in a lower medical category and cannot be detailed for certain tasks or duties.

An ideal precautionary measure is use of ear mufflers by the gunners. Even this, however, is not without problems. Officers say that use of mufflers would restrict hearing and wouldrequire some additional radio communication between the gunners and the commanders.