Silencers, or more properly 'suppressors', were originally designed by Hiram Maxim so that people could enjoy shooting in their backyards without disturbing their neighbors.   During the Great Depression there was some concern on the part of the government that suppressed firearms would be used for poaching livestock by those in need during these trying years.  Suppressors were thus included in the NFA Act of 1934 and subject to registration as well as a 200.00 transfer tax.  Silencers have since been used by gangsters, spies and assassins in the movies and this has given them a somewhat unsavory image.   Most people are of the opinion that silencers are illegal, when in fact they are quite legal in most states.  In many foreign countries they are not only unregulated, but considered quite important for hearing protection and reducing noise pollution. 

While suppressors  certainly offer a tactical advantage as far as disguising the location of  a shooter by both noise and flash reduction, we feel that a much more important aspect of suppressor use is hearing protection at the source of the noise.   My background as an ear, nose and throat physician has given me significant knowledge and exposure to both the causes and effects of noise exposure with attendant permanent hearing loss.  During my tenure in the U.S. Army, one of the most frequent problems that we faced was high frequency hearing loss secondary to noise exposure.  While many of these individuals sustained their hearing loss in actual battle, others were only exposed in training situations.  Even though supposedly adequate hearing protection was provided, these individuals still had hearing loss over time. 

Research has shown that individuals regularly exposed to small arms fire in training situations are over ten times more likely to sustain noise induced hearing loss than individuals not so exposed.  This is despite regular use of protective ear devices, which are supposed to reduce noise levels to below damaging thresholds.  The cause for this phenomenon is most likely due to bone conduction of the noise directly into the middle and inner ears.  While bone conduction hearing is certainly less sensitive than conduction through the normal ear canal, nonetheless the noise levels produced by repeated gunshots are certainly great enough to cause hearing loss over time. 

Use of a properly designed sound suppressor on a firearm is no different than putting a muffler on your car.   A sound suppressor on, for example, a 223 rifle can reduce the noise level from over 160 dB, which is quite harmful, to under 140 dB, which is the OSHA limit for noise exposure.  This cuts off the noise at the source and eliminates dependence on ear protection devices, which are prone to failure.  It also eliminates the risk of bone conduction hearing loss from excessive noise.