MUNCIE, Ind. -- Each year thousands of hunters and recreational shooters suffer hearing damage when they enter the forests and firing ranges, says a Ball State University study. An estimated 50 million Americans are gun owners. Many are  susceptible to noise-induced hearing loss caused by shooting pistols, rifles and shotguns, said William Kramer, a gunfire noise expert and a professor of speech pathology and audiology.

A recent survey of hunters and recreational shooters discovered that many have been wearing hearing protection for only a portion of their shooting careers.

"When you go into the woods or the firing range, there is no excuse for someone not wearing some sort of hearing protection," Kramer said. "All it takes is one shot from your rifle or handgun to leave temporary or permanent hearing loss.

"Once you've lost a portion of your hearing, you never can regain it," he said. "We must protect ourselves from gun noise, which is the most damaging type of noise to our ears."

A recent survey of 350 competitive and/or recreational shooters found that the sport is family-oriented. The average age of the participants was 39 and half were military veterans. Most shooters learned to use firearms under their father's guidance at age 16.

The survey found that the older the shooter, the more likely the participant was to suffer some sort of hearing loss. The youngest 100 shooters reported wearing hearing protection devices for 77 percent of their shooting careers. The oldest 100 shooters have worn protection for the last 39 percent of their careers.

About 58 percent of the respondents reported using cicumaural muffs; 40 percent using closed cell foam (ear plugs); 16 percent using other forms of plugs; and 10 percent using muffs and plugs in combination.

Overall, about 98 percent of the respondents said they had worn hearing protection for only the last 16 years.

"Hearing protection devices have only been widely used since the early 1970s," Kramer said. "The military started using protection only in the late 1960s, leaving millions of former soldiers at-risk for some sort of hearing loss.

"We only started using hearing protection in hunting and recreational shooting when OSHA (the Occupational Safety and Health Act) forced factory workers to wear ear plugs and muffs. It spread into shooting after that."

The survey also found that while the typical hunter fires about 18 shots at game, he or she may take 1,500 to 2,000 practice shots annually.

Exposure to gunfire causes a temporary threshold shift. The symptoms include a temporary loss of hearing and a ringing sound in the ears for a short period of time. Too many temporary shifts will cause a permanent shift, or a permanent loss of hearing and possibly a persistent ringing, Kramer said.

"We like to say that when you been around gunfire too long, shift happens," he said. "For some people, that permanent ringing can be more noticeably loud when they try to sleep. And, when you lose your hearing, it never comes back."