High Speeds, Higher Decibels

Stock car racing is loud. Many fans and drivers like it that way. “Noise is part of NASCAR,” we are often told. We get it. In fact, efforts to reduce the noise in the 1970s by installing mufflers were quickly abandoned because the quiet cars were unpopular with racing teams and spectators alike. The problem is that repeated exposure to noise comes with consequences—permanent and irreversible consequences like hearing loss and ringing in the ears (tinnitus). For many years, those in the industry seemed to accept hearing problems as “part of the job.” As drivers such as Jeff Gordon, Cale Yarborough, and Richard Petty come forward about their hearing loss (see Tania Ganguli’s “Hearing loss an inevitable part of racecar driving” in the Orlando Sentinel, 2/15/2009), we hope others in the industry will begin to take the issue more seriously.

Stock car racing is one of the fastest growing spectator sports in the United States with over 75 million television viewers and more than 8 million spectators attending over 90 racing events each year. Thunderous noise is a given at stock car races whether at a local dirt track or on the national stage such as NASCAR races, and to a certain extent, the noise is part of the sport’s appeal. Despite the seemingly obvious high-noise levels, no scientific measurement of noise levels had been documented. Earlier this year NIOSH scientists published the results of research on noise exposures at stock car events.¹ Research conducted at the Brickyard at the Indianapolis Motor Speedway in Indianapolis, Indiana, the Bristol Motor Speedway in Bristol, Tennessee, and the Kentucky Speedway in Sparta, Kentucky, revealed that noise levels at these tracks often exceed those found in some of the loudest industrial settings.

On Friday and Saturday, August 20 and 21, 2010, NASCAR fans can look forward to the Nationwide and Sprint Cup races at the Bristol Motor Speedway. Bristol has developed a reputation among fans as the noisiest track on the NASCAR circuit. This is mainly due to its bowl-shaped layout (similar to a football stadium), small track size, and metal-constructed stands, which reverberate and amplify the noise generated by the stock cars. NIOSH research confirmed that noise levels at the Bristol Motor Speedway were the highest among the three tracks studied.

Overall, area noise-level measurements taken during race preparation, practice, qualification, and competition exceeded the NIOSH recommended exposure limit (REL) of 85 decibels, A-weighted (dBA) and the OSHA permissible exposure limit (PEL) of 90 dBA. The highest area noise levels were found in the “pit” area. Peak sound pressure levels in the “pit” area at all three race tracks reached and exceeded 130 dB—often recognized as the human hearing threshold for pain.

Personal dosimetry measurements were conducted on drivers, team members, and spectators. The spectator measurements included many workers in the stands such as vendors and security personnel, in addition to fans. The term “spectators” is used throughout to refer to this entire group and to distinguish those working in the stands from those working on or near the track. At Bristol, findings showed time-weighted averages (TWA) that ranged from 96 dBA for spectators in the stands during the race to 114 dBA for a driver inside a car during practice. Peak sound pressure levels exceeded the maximum allowable limit of 140 dB during race competitions. Personal exposure measurements exceeded the NIOSH recommended exposure limit of 85 dBA as an 8-hr TWA in less than a minute for one driver during practice, within several minutes for team members, and in less than one hour for spectators during the race. Another way to look at this is that a driver’s noise dose was 50-900 times higher than the allowable occupational daily noise dose. Race team members receive 12 to 21 hours of intensive noise exposure every week up to 40 consecutive weeks and more during the off-season. Spectators are exposed to a noise dose that is two to ten times higher than a person working a 40-hour week at the maximum allowable limit of 85 dBA. Additionally, race tracks employ workers who are exposed to excessive noise in different events. These workers should consider using hearing protection.

We know there are dangerous noise levels at stock car race tracks and we know that prolonged and repeated exposure to excessive noise levels can lead to tinnitus and noise-induced hearing loss—a permanent, irreversible condition caused by damage to the sensory cells within the ear. So what do we do?

NIOSH and others in the health and safety community recommend removing or “engineering out” the noise as a first line of defense. If mufflers are not used to reduce noise from race cars to a TWA below 85 dBA, then hearing protection must be used. Most racing associations do not require drivers and crew to wear hearing protection devices during practice or race activities, nor do they provide guidelines about the selection or appropriate communication headsets that can provide adequate protection. In certain working environments with excessive noise levels, double hearing protection (earplugs and earmuffs) may be warranted. Newer technologies employing noise cancellation and level-dependent circuitry that provide better attenuation of ambient noise and improve speech intelligibility are now available commercially. Crewmembers should be afforded the same hearing protection currently provided to drivers—that of custom-molded earplugs with built-in speakers. Workers at race tracks and spectators should also be made aware of the noise problem through education and informational campaigns. Most spectators assume that a few hours of recreational noise exposures are harmless, but noise exposures do add up and data from our research show otherwise. When appropriately selected, hearing protection can become a competitive performance advantage—improving communication and preventing long-term noise-induced hearing loss.

Mr. Kardous is a research engineer in the NIOSH Division of Applied Research and Technology.

Dr. Morata is a research audiologist in the NIOSH Division of Applied Research and Technology.

References

1. “Occupational and recreational noise exposures at stock car racing circuits: An exploratory survey of three professional race tracks.” Noise Control Eng. J. 58 (1), Jan-Feb 2010.