What Is a Safe Sound Level?

A 2017 release from the Centers for Disease Control (CDC) reported noise induced hearing loss (NIHL) to be a significant health problem1 affecting an estimated 20% of young adults ages 20 to 29, with that rate increasing to 25% among adults ages 50 to 59. According to the National Institute of Occupational Safety and Health (NIOSH), “NIHL is 100% preventable; however, once acquired, it is permanent and irreversible.”2 It can result from a one-time exposure to a very loud sound or from listening to loud sounds over an extended period. NIHL can lead to communication difficulties, learning difficulties, pain (hyperacusis) or ringing in the ears (tinnitus), and distorted or muffled hearing. The public has the right to be thoroughly educated on hearing health risks in order to make informed decisions about their noise exposure. Both work and public places should provide safe alternatives to noisy environments. This article explores what a safe sound level for the public is and how sound should be regulated.www.shutterstock.com.An environment that seems loud could be damaging your ears. To protect your hearing, the CDC3 and other medical, engineering, and public health officials suggest we turn down the volume; avoid, move away from, or limit exposure to loud sounds; and, as a last resort, use hearing protection devices. The author’s Quiet Coalition: Turn Up the Quiet initiative advocates for these issues to be recognized as important public health issues that can be addressed by simply turning down the volume. No one is injured by quiet and silence, and it usually leads to less stress, increased concentration, and perception.4 HOW DID WE GET HERE? There are decades worth of research and recommendations from multiple sources that we can evaluate to properly understand safe sound levels. In terms of government guidelines, NIOSH makes recommendations to OSHA for worker safety and advises that the best way to prevent NIHL is to limit workers’ exposure to noise. NIOSH established the recommended exposure limit (REL) for occupational noise in 1998 to be 85 decibels dBA over an eight-hour time-weighted average and notes, “Exposures at or above this level are considered hazardous.”5 However, even within these “safe” limits, some workers will develop hearing loss.3 The World Health Organization (WHO) recommends an REL of no more than 80dB for 40 hours per week.6 While workers may have the benefit of workers’ compensation, that does not apply to the general public. NIOSH clearly states that their limits are “not a recommendation for noise exposures outside of the workplace,” and recommends “precautions to protect your hearing by reducing the noise whenever possible.”5 Nevertheless, workplace guidelines are often misused as guidelines for the general public. Furthermore, NIOSH “assumes that the individual spends the other 16 hours in the day, as well as weekends, in quieter conditions.”5 They do not account for noisy activities or hobbies outside the workplace, such as hunting, power tool use, listening to loud music with ear buds, or attending sporting events, movies, and concerts. Some single, brief, intense exposures can cause immediate hearing loss.8 The risk from combined exposure in and out of the workplace requires a correction factor to further reduce the REL.7 WHAT IS A SAFE REL? In 1974, the Environmental Protection Agency (EPA) declared a 24-hour environmental REL of 70dBA over a lifetime will prevent measurable hearing loss. The EPA also notes background levels above 55dBA outdoors and 45dBA indoors can interfere with “spoken conversation and other activities such as sleeping, working and recreation.”8 The EPA states these safe limits “provide a basis for state and local governments’ judgments in setting standards.”8 Later, in 1982, the EPA abandoned public hearing safety when it shuttered its Office of Noise Abatement and Control.9 Unfortunately for the public, that means there is no recognized federal standard to protect hearing. Nevertheless, informed experts recommend following the EPA REL of 70dBA whenever possible. That begs the question, how and where can you find safe places in today’s noisy world? Sound level measurement is complicated. Decibels can be measured at actual levels over the range of hearing (“dBZ,” sometimes referred to as “dB”) or with different weighting scales designed to simulate what the ear might hear.10 The most commonly used frequency weighting system, dBA, was designed for use with softer sounds, with whisper level around 40dB, and underweights loud low-end bass frequencies by as much as 90%.11 The rarely used dBB weighting is designed for midlevel sounds, like a vacuum cleaner at around 70dB. The dBC weighting is designed for loud sounds above 100dB, like those that occur at amplified events. In addition, there are time weightings of Slow (one second rise and decay, which filters out impulsive sounds and is often used with 40dBA soft sounds); Fast (125 microseconds, often used for 100dBC loud sounds); and Impulse (40 microseconds, designed for accurate measurement of bells, beeps, gun shots, jackhammers, sirens, etc.).12 For concerts with impulsive sounds such a cymbals and drums, dBC fast weighting is considered the closest representation of human hearing13 and recommended by WHO.14 Many entertainment permits require measurements in both dBA Slow and dBC Fast weighting, where levels can exceed 120dBA. Unfortunately, many concert venues, regulators, and even some sound engineers and musicians prefer to use dBA Slow weighting because it makes both loud-sustained and impulsive sounds appear quieter,15 even though that increases the risks for workers, patrons, and neighbors. Studies have found that 30% of rock and over 50% of classical musicians have some degree of hearing loss,16 and similar levels of tinnitus.17 Many musicians and dancers want to “feel the noise” and develop hearing loss that leads them to turn up the volume even louder while their colleagues may be afraid to ask to turn the music down.18 Measurements are also not often made at the source of the sound. For example, 120dBA at 100 feet away is equivalent to 132dBA at 25 feet away,19 where injury can occur in less than one second.20 Precision sound measuring equipment21 records the actual sound plus all the various frequency and time weightings simultaneously and should be measured at multiple locations for a clear understanding of the noise environment. Although the public generally knows that loud sounds can be risky, they may not be aware of how much risk they are exposed to every day. For example, hospitals, schools, and offices have noise-activated warning signs22 designed to regulate noise levels by lighting up green for recommended safe levels up to 60dB, yellow up to 75dB, orange up to 85dB, and red above 85dB. There are instances, however, where these signs are used to encourage crowds to make noise. Larson Davis is “helping football teams use our products to make some noise!” Their meter “integrates seamlessly with scoreboards” to “improve the fan experience” by measuring the “extremely high level of noise.” They proudly proclaim, “our meters measured the Kansas City Chiefs’ crowd generating 142.2 dB of noise,” when they “successfully took the title of loudest stadium.”23 What is the public to think when the same company that warns about noise over 60dB then celebrates excessive noise over 140dB? CAN HEARING PROTECTION HELP? Will earplugs and earmuffs protect you? Not as much as you might think. Even though they offer limited protection, when it is not possible to reduce noise exposures to safe levels, hearing protection is necessary.24 The noise rating reduction (NRR) standard created by hearing protection manufacturers is not a reliable source for regulation, as it overstates protection by up to nearly 2,000% in some cases. It is not approved for use by NIOSH which recommends “the labeled NRR be derated by 70%” for earplugs that aren’t formable.27 In other words, the best you can expect in the real world is half the protection for certain non-impulse sounds. Some people use “double protection” with both earplugs and earmuffs, but rather than adding the two NRR numbers together, you simply add five more decibels of protection to the device with the higher NRR. For example, using earplugs with an NRR of 29 and earmuffs with an NRR of 27 would provide a total NRR of approximately 34dB.25 Then one needs to reduce the NRR by 50%, and the “estimated” protection for certain non-impulsive sounds becomes closer to 17dB. Even using the NIOSH worker “safe” REL of 85dBA, double protection is ineffective above 102dBA. For the public using the EPA REL of 70dBA, double protection is ineffective above 87dBA. In addition, hearing protection is not beneficial in places where communication is required like stores or restaurants, due to an “occlusion effect,” which causes your own voice to sound unusually loud.26 Communication is even more difficult when both parties are wearing hearing protectors, which can distort the direction from which sound is coming or fail to separate it from background noise (the “cocktail party effect”).27 Active Noise Canceling (ANC) claims are also unregulated, and tend to be “more effective at canceling continuous or predictable sounds than sudden or unpredictable ones.”28 They may be helpful when you are on a plane, but not at a loud sporting event, nightclub, or concert. If you have tinnitus, hyperacusis, or other sound sensitivities, the use of hearing protection is generally not advised.29 Earplugs deprive the auditory system of sound, and the ears try to compensate by making quieter sounds louder, which may exacerbate the condition.30 HOW RISKY IS NOISE EXPOSURE? Studies have shown that as many as one in five young people may already suffer from hearing damage because of the constant use of ear buds.32 WHO notes 50% of people ages 12 to 35 are at risk of hearing loss due to prolonged and excessive exposure to loud sounds,33 and recommends limiting ear bud use to 60 minutes a day. As for those with hearing aids, as the severity of hearing loss increases, the ability of hearing aids to help one hear better often decreases and surgery or cochlear implants may be necessary.34 An audiologist and otolaryngologist should be consulted to evaluate the severity of loss, advise on how to prevent further injury, the range of technical options, and how to identify and treat the related impact on communication, concentration, anxiety, depression, social isolation, and loneliness. OTC hearing aids can be a cost-effective option for informed consumers with mild to moderate hearing loss. In September 2024, the FDA authorized Apple’s Air Pods Pro 2 as an OTC hearing aid for adults.35 Apple is promoting Air Pods Pro 2 as an “all in one hearing health experience,”36 to also be used as a hearing aid and for hearing protection. Apple says the product is suitable for use to listen, aid, and protect “throughout the day.” The fine print, however, notes that “[t]he Hearing Protection feature is not suitable for protection against extremely loud impulse sounds […] or against sustained sounds louder than 110 dBA.”36 Recorded levels at music concerts frequently reach 139dB42 and levels at sporting events can exceed 140dB.38 Sound from personal listening devices and loud music venues may reach 120dB for hours on end.19 Can these products create a problem, but also be the solution to it? REGULATION TO PROTECT THE PUBLIC Sound is supposed to be regulated with limitations on sound levels and/or permitted time periods.39 Public safety requires a combination of properly drafted regulations, accurate records, independent oversight, accountability, and due process. Although the EPA, state, and local governments are charged with enforcement, for a number of reasons compliance is often underfunded and relegated to low priority with no monitoring equipment, no training and no one assigned to enforcement.40 While the general public is “largely aware of the hazard posed by high sound levels,”41 we are going from one noisy place to another without warning or adequate protection. Unless you live your entire life in a sound proofed bubble, or the middle of an empty field, you will be exposed to unsafe sound every day. Going to sporting events, concerts, movies, and even restaurants may cause permanent hearing injury. The cumulative effect of regular exposure to “approved” levels of 105, 110, 115, and 125 dBA,42 with actual levels up to 140dBA, is a recipe for a society with increasingly severe and irreversible hearing impairment. Disclaimer: This content is provided for general informational purposes only and may not reflect the current law in all jurisdictions. No information contained in this article should be construed as legal advice nor is it intended to be a substitute for legal counsel on any subject matter. Readers should consult their own advisor for legal or other advice.