In September 2007, a U.S. Navy officer working with the Marines' executive safety board issued a simple, stark warning. According to a presentation by Cdr. Stan Jossell, the Marines -- and to some extent the services in general -- are buying new equipment that is so loud that it's not a matter of whether but when and how badly operators will suffer permanent hearing damage. Jossell noted, moreover, that the technology to protect users from damage does not yet exist.

Jossell, who declined to be interviewed for this article, singled out the F-35 Joint Strike Fighter and the Expeditionary Fighting Vehicle (EFV) as particular problems. Noise levels for these systems "will result in permanent hearing loss," he wrote. "We are not protecting our people . . . [Program Executive Office] Tacair has accepted the 'serious risk' for the F/A-18E/F and EA-18G engine noise. Yet we are actually accepting the probability of permanent injury, not the risk of the occurrence."

Hearing loss is expensive. Jossell's study found that the cost for treating hearing loss among all veterans was over $900 million in 2006 -- up from about $200 million in 1996 -- and that with new technologies coming on line, the Navy and Marines are placing their personnel "in work environments where permanent hearing loss is a given." The problem, the report concludes, is that "we continue to design and procure weapon systems so loud that even the best noise attenuation possible cannot prevent hearing loss."

What has made the problem worse? Essentially, noise levels are associated with performance. The EFV has a 2,600-hp. diesel engine to drive it through the water at a maximum speed of 25 kt. -- substantially more power than an M1 tank -- and there is only so much that can be done to reduce noise inside its personnel compartment.

The latest generation of fighters, including the F-22 and Super Hornet as well as JSF, use engines that generate more thrust per unit of airflow than earlier engines. This inevitably means higher jet velocity and that aircraft noise will rise as the fourth power of the velocity along with thrust. While most fighters expose ground crews to full-throttle noise for moments, the Stovl F-35B puts out almost 40,000 lb. of thrust for tens of seconds as it descends to the deck.

Modern aircraft can put out 150-plus dB. of noise at close quarters. The best protection -- foam earplugs and active noise reduction (ANR) headphones -- only protect hearing to 134 dB. Passive measures provide about 30 dB. of noise reduction, which is nowhere close to the U.S. Labor Dept.'s mandated 85-dB. exposure limit over an 8-hr. workday. What's more, even the 30-dB. reduction isn't being met by the vast majority of sailors. According to recent reports, Naval Air Systems Command estimates that only about 7% of sailors insert earplugs correctly.

The problem can to a degree be mitigated by limiting exposure. (One source suggests that the Royal Navy expects to limit its deck crews to 2 hr. on deck at a time during JSF operations.) However, that's not a practical solution for occupants of an EFV, and would be a serious limitation for carrier operations. Also, incorporating ANR into a combat helmet would add more complexity to a soldier's equipment. The EFV's drivers will have Bose ANR systems built into their helmets, but that's not planned for the troops riding in back.

A 2006 Navy survey conducted by the Naval Air Warfare Center Aircraft Div. found that hearing loss claims have risen consistently with the U.S. Veterans Affairs Dept. across all services. According to the Navy Times, around 840,000 veterans have service-related hearing loss, making the disability the largest category of service-connected disabilities paid by the Veterans Affairs Dept. The Naval Safety Center also estimates that hearing-related disability payments to former sailors rocketed to $108 million in 2004 from $65 million in 1999.

The Navy is out to change all that, but the technology is not yet there. A 2005 study by the U.S. Air Force Research Laboratory (AFRL) examined a joint Air Force-Navy approach to improving hearing protection as well as mitigating hearing loss. The goal of the program, launched in 2001, was to develop a hearing-protection system that protects personnel working around 150 dB. for up to 15 min. a day. (Large jets such as the F-15C and Joint Strike Fighter operate in the 144-152-dB. range.) The goals were established for near-, mid- and long-term attenuation: 35-40 dB. by 2004, 40-45 dB. by 2006 and 45-50+ dB. by 2008. The near-term project focused on improving passive protection, the mid-term goals introduced ANR and the long-term goals included ANR as well as passive bone conduction control.

The good news is that near- and mid-term goals to develop up to 45-dB.-level protection were reached. Custom-shaped earcups provide a 4.4-dB. improvement over the standard flat earcups. Passive custom earplugs worn under standard earmuffs were one step better, and ANR custom earplugs achieved 47 dB. of overall attenuation.