CHAPTER FOUR
Recreational Noise
Brian J. Fligor, Sc.D.

Industrialized countries have made remarkable economic progress since the middle of the 20th century. Much of the economic success has been fueled by noisy industries, which gave rise to a huge middle class. The result is that we have had decades of a relatively stable workforce with a steady paycheck and disposable income to engage in recreational pursuits outside of work. People employed in manufacturing, construction, transportation, and mining have been able to afford a house, a car, and have a little money left over to have some fun on evenings and weekends. While the paycheck is necessary, many jobs do require workers to be around loud sound for long periods of time. Since the Middle Ages, we’ve known that blacksmiths were at risk for hearing problems because of hammering away at metal all day. In the 1800s, “boilermaker’s deafness” was reported in men working in steam boiler shops, for the same reason (metal hitting against metal, and the resulting constant loud noise). Thankfully, the risk for hearing loss associated with noise in the workplace is fairly well understood now and government regulations are in place to limit the risk prolonged noise poses to the individual worker. While the effectiveness of those work-based hearing loss prevention programs is a matter of continuous scrutiny, a less-often studied issue is what people do when they are not on the job. How do they spend that disposable income? Recreational activities such as hunting (and other recreational shooting), hobby woodworking, snowmobiling and four-wheeling, going to sporting events and NASCAR races, and listening to music (either at a concert or through headphones or in-ear earphones) all contribute to a person’s lifetime sound exposure. Oftentimes, we use sound to combat the intrusion of someone else’s noise, such as a person living in the city turning the television on at night to block out overnight traffic noise, or a teenager turning up headphones to block out the “Easy Listening” station his parents have on the car stereo. Our world is a noisy place, by our own doing.

Much of this topic is covered in greater detail in other chapters, but the basics are covered here for the sake of putting recreational noise exposure in perspective. Permanent hearing loss can occur when a person is exposed to sufficiently high levels of noise for a long enough period of time. This fact has been known for a very long time and protections have been put into place for the most commonly noise-exposed population: people in the military and people working in noisy industries. The most widely known federal regulation protecting against occupational noise-induced hearing loss (NIHL) is the Hearing Conservation Act of 1983, and the Occupational Safety and Health Administration (OSHA) is tasked with its enforcement.1 This piece of legislation sets a maximum allowable noise dose (which describes the combination of sound level and the amount of time a person is exposed) to protect a large percentage of people. However, these regulations set only minimum safety standards, only apply to the occupational setting, and, per OSHA, admittedly do not protect a significant subset of the population. Even with protections in place for the workforce, NIHL is the second most common form of acquired hearing loss, second only to age-related hearing loss. Additionally, the National Institutes of Health (NIH) have acknowledged that non-occupational noise exposure is a significant threat that affects the hearing of children, adolescents, and adults. Other, more conservative standards are used in some countries, and are recommended for non-workers, such as children.

NIHL is a permanent hearing loss caused by damage to the inner ear, and is cumulative throughout one’s lifetime. The most common cause is from extended exposures to moderately intense sound levels, above 80-85 dBA (A-weighted decibels sound pressure level), and develops insidiously over months or years. This type of gradually developing NIHL occurs when the sensory cells in the inner ear are overworked and die (see Chapter 2 for greater detail on how this happens). These cells are not replaced by new sensory cells in the inner ear, and so the resulting hearing loss is permanent. For more intense exposures, such as from impulsive noises of 132 dB and higher or very high-level continuous noise, damage occurs not only because of overworked sensory cells, but because the sound pressure passing into the inner ear is sufficient to tear apart the fragile structures that are responsible for hearing. This type of damage is also permanent and can occur immediately after a single exposure to such intense sound levels, and as you may have read in this book already, is referred to as acoustic trauma.