The positive Effects of noise cancelling ear protection on the human ear and brain can be enormous. They prevent the onset of hearing loss, mental stress, irritability, insomnia and many other side effects of impulsive noise. The manufacturers have the responsibility of conforming to ANSI S-3.19 and CE-EN-352.1 standards in the design and production procedures. The users have the responsibility of following the safety instructions while wearing the protection devices. They also need to follow the maintenance procedures as printed on the product labels and procedure manuals. This can ensure complete protection and extended lifetime of the products.
Mechanism of Noise Cancelling Ear Protection
The various paths followed by the muzzle blast noise to reach the ear protection device can be graphically plotted on the 3 coordinates of X-Y-Z. The net volume of noise in terms of decibels is to be calculated at the most sensitive part of human ear to noise, which is the rear ear portion.
- The strength of noise waves can be cancelled when an equal and opposite set of waves are set in motion, opposite to the original direction of the sound waves. But in the case of non battery operated protection devices this may not be possible. Hence the design of the ear cups and the foam material layers within the cups need to be compatible to deflect or absorb the waves.
- The extent to which they are able to perform the noise cancelling ear protection is measured at the 98th percentile of the protection value. Any device which can conform to the ANSI and CE-EN standards will be able to deflect more than 98% of the noise entering it.
- The next parameter to be considered is the time duration for which the device is able to function at 98% efficiency. For example a shooter practicing within a sports training zone may be exposed to peak levels of impulsive noise after every 5 minutes. If he stays within the premises for close to 4 hours, he will be exposed (60/5)*4 = 48 times. The device should be able to protect his ears consistently at the same level of efficiency.
- Assuming the value of NRR standard range to be from 0 to 35, an efficient noise cancelling ear protection system needs to maintain the NRR value between 30 and 32. This is for the impulsive noise which measures above 164DB.
Selection of Noise Cancelling Ear Protection
The protective device chosen by the user needs to conform to the NRR rating prescribed for shooting zone applications. The extent of noise cancelling ear protection depends on the range by which the original intensity is reduced.
Tests on muzzle blast wave intensity before cancelling and after are measured by sensor mounted devices. If the cancellation is close to or greater than 98%, the device is recommended for usage after exposing it to 8 hours filed testing.
ClearArmor 141001 Shooters Hearing Protection Safety Ear Muffs have been certified after some of the harshest tests conducted on them for noise cancelling ear protection.