Noise-Induced Hearing Loss
Preventing Irreversible Damage
We live and work in a noisy world. Fire alarms, factories, concerts, subways, and explosions are just a few sources of excessively loud sounds.
Yet our sense of hearing is not something we can turn on and off. As a result, our ears can be intentionally or unintentionally assaulted with sounds loud enough to cause permanent hearing damage. We can also develop tinnitus, more commonly known as ear ringing.
A common misconception is that noise-induced hearing loss (NIHL) occurs immediately and is obvious to the listener. In fact, auditory damage due to hazardous noise exposure typically happens gradually over time. Unfortunately, current surveillance programs for hearing loss prevention often detect hearing loss only after it has occurred, when opportunities for prevention and early intervention have already passed.
Noise-induced hearing loss is common among members of the military as well as in individuals working around loud machinery. Currently, the risk of NIHL in military personnel is the highest it has been in 30 years. The Veterans Administration has reported that disabilities of the auditory system, including tinnitus and hearing loss, were the top two most common type of service-connected disabilities, accounting for nearly 18 percent of the total number of disabilities among veterans in 2010. Currently, VA compensation claims exceed $1 billion for this typically preventable injury.
Dr. Deanna Meinke, professor of audiology at UNC, is presently conducting research funded by the Office of Naval Research to develop sensitive techniques for the early detection and monitoring of NIHL, while intervention is still an option for those being affected.
Current research efforts involve the development of hardware, software, distortion product otoacoustic emission (DPOAE) mapping processes, and analysis strategies. DPOAEs are extremely low-level sounds emitted by the ear in response to tones and are detected with a sensitive “microphone” in the ear canal. Because there are only subtle differences between people with normal hearing and those with hearing losses, it is important for the research team to follow individuals with NIHL over time to account for any significant changes on an individual basis. Dr. Meinke conducts this valuable research with three audiology graduate students at UNC, colleagues at Dartmouth Medical School, and collaborators at Creare Inc.
“We have a snapshot at the start of the project and at six to twelve months later. Individual [DPOAE] maps are generally consistent — we are interested in detecting the change [in DPOAEs] over time,” Dr. Meinke said. “We also hope to determine what parts of this map we should be focusing on in order to detect the changes early as well as to minimize the testing time.”
Dr. Meinke’s other research interests focus on the development of ear probe systems, hearing conservation software development, measurement of impulse sound levels from recreational firearms, noise exposure assessments for both children and adults, hearing protector attenuation in children and the development and implementation of educational programs targeting youth. Many of these interests are pursued with assistance from UNC audiology student researchers and UNC colleagues in Audiology & Speech-Language Sciences.
“Not only does hazardous noise cause you to lose sounds you enjoy, but they might be replaced by a never-ending unwanted sound (tinnitus). If an individual permanentlyloses hearing from noise damage, he or she should visit an audiologist and be fitted with hearing aids,” Dr. Meinke advises. “For those individuals who develop tinnitus, they either learn to tolerate the ringing and buzzing sounds or may need to undergo treatment therapies and perhaps wear ear-level devices to help tune out their own ear sounds. If someone participates in noise hazardous activities, he or she should have hearing monitored regularly to check for subtle changes and ensure the effectiveness of the hearing protection devices.”
Besides conducting research, Dr. Meinke also focuses on prevention efforts by serving as a faculty member of Dangerous Decibles educator workshops, which are conducted in the U.S., Canada, and New Zealand. K-12 classroom presentations teach children to value their hearing and implement specific strategies for preventing noise-induced hearing loss and tinnitus based upon health communication theories. She feels it is critical that her research contribute not only to the scientific knowledge base but also be transferred to the public through improved services, community outreach, and public health education. Dr. Meinke emphasizes that “noise-induced hearing loss is preventable and an unnecessary consequence of lifestyle, occupation, or environment.”