Research | September 2017 Hearing Review
A question that can lead to better hearing health awareness for a lifetime. Here’s why.
While the authors don’t wish to spoil anyone’s party, the loudness of exploding balloons—which can exceed the noise levels of a 12-gauge shotgun and a 30-06 rifle—is a good way to inform and educate both adults and children about the potential hazards of loud impulse noises. The intention of this research is not to have balloons banned from society any more than it is the intention of skin cancer research papers to dissuade people from going outdoors on sunny days. This paper is about raising consciousness about a topic that society does not yet spend enough time discussing: cumulative noise exposure from childhood into adulthood.
The bag of party balloons in front of me (Unique Industries© Inc, Philadelphia) has the following warning labels:
- This bag is not a toy;
- Choking hazard, and
- To protect eyes from possible damage, the use of a balloon pump is recommended.
There is no mention of hearing protection or the risk of intense sounds. However, there is a growing body of literature on the potential hazards of high-intensity impulse noises, the kinds that occur from gunshots and explosions.1-4 While we suspect the general public would have no difficulty imagining that firecrackers and gunshots are potentially hazardous to hearing, we were interested in the risks of what might be considered a much more benign and child-friendly item: the party balloon. Specifically, we sought answers to the following three questions:
- What are the peak sound pressure levels of exploding balloons?
- How do the levels of exploding balloons compare to other high-intensity impulse noises?
- Are the levels intense enough to warrant concern about potential long-term hearing damage from impulse noises?
Recently the World Health Organization (WHO) reported that 1.1 billion children and teenagers are at risk for long-term hearing loss as a result of noise exposure.5 Data from the National Health and Nutrition Examination surveys in the United States revealed that the prevalence of hearing loss in teenagers has increased nearly 5% from 1988-1994 to 2005-2006.6 Determining a direct cause for this increased prevalence is not trivial; however, a potential link is noise exposure from leisure or fun activities.
In the workplace, there is a much greater understanding (and acceptance) of the risk of temporary or permanent hearing loss from noise exposure. If the workplace environment is sufficiently noisy, there are laws that require employers to provide solutions (eg, hearing protection, limited exposure time, signage, etc) for their workers.7 These laws vary slightly by state or province; however, many jurisdictions use an 85 dB (A-weighted) limit for 8 hours with a 3 dB exchange rate. This means that if the level of the environment is 85 dBA then it is considered safe to be in that environment for 8 hours without the need for hearing protection and with limited long-term risk of hearing loss. However, as the level increases by 3 dB, the amount of time that it is safe to be in that environment (the maximum allowable daily noise dose) is halved. In other words, at 88 dB, the recommended safe time drops to 4 hours; at 91 dB, the time drops to 2 hours, and so on. It is the combination of level of exposure and the time allowed that determines the maximum allowable daily noise dose for an individual.
Several researchers have taken the workplace approach to calculating maximum permissible daily noise doses for leisure activities. For example, Hodgetts and Liu8 found that, during the Stanley Cup hockey finals in 2006, the noise levels in the Edmonton Hockey Arena reached a maximum allowable daily noise dose of around 6 minutes. However, the games lasted about 3 hours each. Other researchers have used similar calculations to assess the listening levels of smartphones and other personal music devices.9,10
One criticism of this approach is that the safe listening recommendations are based on data from cumulated noise exposure over many years in an industrial context. Many leisure activities are short-lived and non-recurring. For example, while hockey noise is significant and disconcerting, an argument can be made that, unless you are a full-time employee who attends every game, the occasional exposure is likely not the same as the cumulative exposure over the lifetime of an employee in a noisy factory. Therefore, it has been argued that risk estimates derived from industrial noise should be interpreted with some caution when applying them to leisure noise.10
So far, we have been discussing noise exposure that is more or less continuous over a period of time. Another noise type, impulse noise, is characterized by a sudden burst of high-intensity energy. The impulse noise creates an intense air pressure change that can have a significant impact on the auditory system. Impulse noises (typically explosions) have the potential to create large waves in the basilar membrane of the inner ear causing damage to the delicate hair cells.11 Recent research has also shown that noise damage can occur even beyond the cochlea in the synaptic gaps between the inner ear and the VIIIth nerve (often referred to as “hidden hearing loss”).11
Occupational standards also contain hearing risk estimates based on impulse noise.7,12 A number of recent studies have looked at various methods of calculating maximum permissible exposure (MPE) based on impulses.1-4,12-15 These approaches vary in how conservative they are at estimating risk, with some approaches predicting more damage than others.
A universally agreed-upon method has not been established, but Flamme et al2 provided a thorough review of the various approaches. They measured the sound pressure level (SPL) of various firecrackers and found that at 0.5 m the peak SPL was around 171 dB. Given that intensity, the most liberal calculation for MPE estimated that subjects could be exposed to two firecrackers at that distance, while the most conservative method of calculating MPE suggested that zero exposures would be safe at that distance. Similarly, Flamme et al2 measured civilian firearms and found that they ranged from 141 dB SPL for a Marlin 60 .22 caliber rifle to 164 dB for a Smith and Wesson .38 caliber handgun. Again, they provided estimates that ranged from a few exposures to zero safe exposures, depending on the method of calculating MPE.
With this in mind, we set out to determine if there was any reason to be concerned about potential hearing risks associated with balloons exploding. Specifically, do balloons produce an acoustic pressure wave on par with other well-known explosive sounds? And if so, should we be concerned about children playing with and popping balloons?
Instrumentation. The authors used standard 9-inch party balloons for all measures (Unique Industries© Inc, Philadelphia). The measurement setup consisted of a ¼-inch constant-current power (CCP) pressure microphone-preamplifier set (GRAS Type 46BG) with a sensitivity of 0.2 mV/Pa, and a 2-channel CCP power module (GRAS Type 12AQ) with adjustable gain (-20 dB to 70 dB in discrete steps of 10 dB) and selectable filter (Linear, High-pass, A-weighting, External) settings. The microphone-preamplifier set has a bandwidth of 3.15-70 kHz and dynamic range upper limit of 184 dB SPL. All but the 0 meter measurements (described below) were made at grazing incidence to the sound source, and all measurements were made with the power module set to apply 10 dB gain.
Measurements were carried out within a single day; the measurement setup was factory-calibrated less than 2 months from measurement date, which was well within the suggested annual calibration. Data were collected at 250kHz with a 16-bit National Instruments USB-6210 data acquisition (DAQ) module set at ±10V range. A custom LabView program was used to control all measurement equipment and data collection. Data were saved to text files and post-processed in MATLAB® using custom MATLAB® scripts alongside a US National Institute for Occupational Safety and Health (NIOSH)-developed MATLAB® library; this library was also used by Flamme et al1,2 and Meinke et al3,4 to analyze impulse noise data. The MATLAB script used for the calculations were the same script used for the gun noise levels included in this paper (see online version of this article for details).
Procedures. We were interested in the level of impulse noise at 4 distances from the micro-phone: 0 meters, 0.5 meters, 1 meter, and 2 meters. We were also interested in the impulse level when “inflated-to-pop” (blown up to the point of explosion) vs “crushed- to-pop” vs “pin-popped.” The authors wore industrial-grade ear protection for all measurements.
For the “inflated-to-pop” condition one of the authors blew air into the balloon to the point that it ruptured (Figure 1). This was repeated 10 times at each distance with all post-processed results being averaged to obtain mean values. For the “crushed-to-pop” and “pin-popped” conditions the authors first measured a piece of string to 28.3 inches in length (circumference = 3.14 x 9 inches). This string was then used as a 9-inch guide by inflating the balloon to the point where the largest section of the balloon fitted into the loop of string. We realize that the circumference of a balloon is not a perfect circle, however, we felt this provided us a reasonable calibration for the prescribed 9-inch diameter. We obtained 10 measures of crushed-to-pop and pin-popped at 0 meters from the microphone. These 10 measures were then averaged for a mean peak dB SPL for both conditions.
Table 1 shows the main findings from this experiment. As expected, the worst-case scenario was when a balloon was inflated to rupture at the entrance to the microphone. This would be the equivalent of a person blowing a balloon to rupture right beside another person’s ear. Mean peak SPL in this scenario was 167.82 dB with a standard deviation of 3.75 dB. At this level, the impulse noise may represent approximately the 8-hour equivalent exposure of 81.35 dB (SD = 2.54 dB). We used the A-weighted 8-hour sound equivalent level (LeqA8hr) method outlined in the Direction Technique de Armements Terrestres (DTAT) 1983 standard16 and used in Meinke et al3,4 to calculate approximate maximum permissible exposures (MPE) for both adults and children. We found that adults may be able to sustain between 2-3 exposures of this level before running the risk of permanent damage. However, for children, not even 1 exposure would be considered safe when a balloon is inflated to rupture near the ear. Predictably, as we moved the exposure further back from the microphone, the average peak dB SPL decreased and the MPEs increased (see Table 1). Both the “crushed-to-rupture” and “pin-popped” conditions were found to be lower in average peak dB SPL and MPEs than the inflated-to- rupture conditions.
Figure 2 shows a comparison of the “inflated-to-rupture” 0-meter condition in comparison to other recently-measured impulse noises.1,2 While slightly lower than a 357 Magnum, the balloon impulse noise was found to exceed that of a 12-gauge shotgun and a 30-06 rifle.
Our initial objective for this experiment was to explore whether two concerned fathers had any justification for their disdain of children’s party balloons. While we felt they may be potentially hazardous, we were alarmed to discover that they were capable of producing impulses that were around the same level as a high-powered shotgun or a 357 Magnum. For children in particular, balloons produce an impulse noise that may be considered potentially hazardous—in some cases even after only 1 or 2 exposures. We are fairly confident that parents would not let their children shoot guns without considering hearing protection.
It is important to point out that risks associated with maximum allowable daily noise doses assume that these exposures will be occurring for a long period in a person’s life (eg, years). It is also true that the calculation of MPE from impulse noises is an area that is not completely understood or agreed upon.7 However, it is difficult to imagine how we might actually find an answer to these challenges associated with these estimates since it would be unethical to pursue controlled long-term exposure on impulse noises in humans. For example, a recent study17 on animals showed that ears exposed to only 2 hours of 100 dB demonstrate significantly greater loss as they aged compared to control animals. Additionally, there was a significant interaction between amount of exposure and age of animals. Higher exposures when the animal was young led to more rapid declines as the animals aged.
Noise exposure is cumulative in the same way as sun exposure,18 and we need to be thinking of noise exposure in our society like we now think of sun exposure. The intention of this research is not to have balloons banned from society any more it is the intention of cancer research papers to have society banned from going outside on sunny days. This paper is about raising consciousness about a topic that we do not yet spend enough time discussing. We appreciate that it is fairly easy to consider papers such as this, and the people who write them, to be hyper-concerned parents dedicated to generating yet another warning label that takes away the joys of being a child. In fact, balloons are not banned from play in either authors’ homes. The children in our houses are aware of balloon noise and are educated about the risks of popping them.
To our children, wearing sunscreen is not a behavior they will need to learn; it is what you do when you leave the house on a sunny day. We believe that changing the minds of teenagers and adults about hearing protection is an important challenge. Changing the mindsets of parents with small children—as well as daycare centers and schools—about the impacts of noise on lifelong hearing will probably lead to greater social and societal change in the long-term.
This is the context for this paper. We want physicians and hearing care professionals to have an interesting starting point for conversations with parents of young children. We want parents to talk to other parents about noise and how to protect against unnecessarily loud environments for their children. We want daycare centers and schools to be aware of the long-term hazards of even one large exposure.
To our children, they just know and accept that sunscreen is important because we have learned enough about it and made it routine for them. Our hope is that, by the time our children have children, they will know and accept that hearing protection is important and it will be routine for their children. It all starts with conversations like “Do you know how loud balloons can be?” ?
A version of this article was originally published at www.canadianaudiologist.ca (Vol 3 , No 6) and appears here courtesy of editor Marshall Chasin, AuD, and the publisher.
Correspondence can be addressed to HR or firstname.lastname@example.org
Original citation for this article: Hodgetts B, Scott D. Do you know how loud balloons can be? Hearing Review. 2017;24(9):16-20.
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