During the rain delay in the golf Players Championship on television, I attempted to justify the time I was spending watching a “good walk ruined” as Mark Twain was fond of saying. The announcers were commenting on how far the ball was now being driven, and in a moment of brilliance I had my justification for watching. The comment reminded me of a report published a couple of years ago by an ENT group in England who offered the suggestion that the titanium drivers used by golfers could be responsible for hearing loss – based on a single patient and some SPL measurements made while a professional golfer hit golf balls with a series of the large-faced titanium drivers.{{1}} [[1]] Is golf bad for your hearing? British Medical Journal, 2008; 337:1437-1438.[[1]]
This report was published with a great deal of sensationalism, suggesting that the sound levels made upon hitting the ball are a likely source of hearing loss (is this beginning to sound like other familiar crises based on limited information?) and that golfers should be so advised. So, to those who think that golfers are blind to fashion, could they now add hearing loss to their criticism of golf?
The report, printed in the British Medical Journal stated that ear specialists from England suspect the “sonic boom” the metal club head makes when it strikes the ball damaged the hearing of a 55-year-old golfer they treated for unexplained tinnitus and reduced hearing in his right ear. Their tests confirmed that his hearing problems were typical of those seen with exposure to loud noises.
As a result of this, and from comments made by other golfers that the new drivers did indeed sound different, the doctors decided to recruit a professional golfer to hit shots with six thin-faced titanium clubs from manufacturers such as King Cobra, Callaway, Nike and Mizuno. They found that all produced a louder noise than standard thicker stainless steel drivers. The worst offender was the Ping G10 at over 130 decibels (Figure 1). They found that all six titanium clubs exceeded safe limits (identified as impulse noises exceeding 110 decibels), while only two of the six steel drivers posed a hazard.
The Report’s lead researcher, ENT Malcom Buchanan, M.D. concluded that “thin-faced titanium drivers may produce sufficient sound to induce temporary or even permanent cochlear damage in susceptible individuals.” As a result of their findings, they advised that players who use these new generation of thin-faced titanium drivers to propel the ball further should consider wearing ear plugs.
Figure 1. Comparison of peak emitted sound levels (dB) between thicker faced stainless steel (yellow) and thin faced titanium (red) golf drivers when hit three times by a professional golfer
The authors did state that there have been no population studies to date on damage due to golf clubs (Tiger may disagree), and, while golf may be popular among retirees suffering from age-related hearing loss, there has been no indication of increased inner-ear damage among younger, healthier players. They suggest that this may be because titanium clubs have become popular only in the past decade, and ultra-thin-faced clubs even more recently. It is also possible that golfers have suffered slight hearing loss without even realizing it.
Regardless, a crisis had set in, based on a “n” of one.
Interestingly, others looked at this then with some interesting observations, none of which were as sensationalist as the original report. And, whether we like it or not, the news media deals primarily in sensationalism. The other reports essentially went unreported.
Questions Related to the Study
1. Figure 2 shows the audiogram of this single source of panic.
Figure 2. Pure tone audiogram showing sensorineural hearing loss on the right, with a noise induced drop at 4-6 kHz
The audiogram shows that there could, or could not be asymmetry between the ears. Because pure-tone thresholds are obtained in 5 dB increments, it is possible that the ears have essentially the same audiometric thresholds. Repeated measurements would be required to obtain this information. Repeat measurements were not reported, even though they might have been made. So, the audiogram may or may not be good evidence identifying this as a one-sided noise-induced hearing loss.
2. When hitting a golf ball, is the right ear more exposed than the left for a right-handed golfer? Proper position for striking the ball requires that the head is lined up directly at the golf ball and is to remain steady until after the ball is hit. However, if it did, any hearing loss should be symmetrical. Keeping the head still does not always happen, but try to hit a golf ball with your head moving away from the ball before you strike it (or in this case, miss it, so there would be no sound other than a swish). Also, binaural SPL measurements show that a right-handed golfer is exposed to higher levels at the left ear than the right, presumably because the sound sources (clubhead and ball) are moving rapidly away from the right ear.
3. How many balls would one have to hit to exceed damage risk criteria? Tepper, et. al. commented that the brunt of the impulse noise from golf clubs comes within the first 10 msec after impact.{{2}} [[2]] Coefficient of restitution. Replies to: Is golf bad for your hearing. British Medical Journal. Sport. Dec. 29, 2008, Feb 9, 2009. http://www.bmj.com/content/337/bmj.a2835.extract/reply.[[2]] Using the 130 dB SPL high end level and a 3-dB exchange rate (the most stringent method) to determine safe exposure levels, a person would be allowed to hit 200 drives within a 24-hour period before hearing protection would be necessary.
4. Clubhead speed is something that should be taken into consideration. The upper level of almost 130 dB SPL was measured for a professional golfer. This requires generating a clubhead speed of up to 120 mph. The average golfer generates a clubhead speed of about 85-90 mph, resulting in a significantly reduced SPL.{{2}} [[2]] Replies to: Is golf bad for your hearing. British Medical Journal. Sport. Dec. 29, 2008. http://www.bmj.com/content/337/bmj.a2835.extract/reply.[[2]]
5. Based on material’s anaylsis, which is louder, steel or titanium? Mr. Giljohann, an engineer wondered why titanium is louder than steel, and considered two aspects of the materials: material damping and Young’s modulus.{{3}} [[3]] Why is titanium louder? Material’s analysis. Replies to: Is golf bad for your hearing. British Medical Journal. Sport. Dec. 29, 2008, Feb 9, 2009. http://www.bmj.com/content/337/bmj.a2835.extract/reply.[[3]] Based on material damping, he says that with a damping of approximately 0.1% by both, dependency on damping would not seem to be a factor. The Young’s modulus of steel is higher than titanium and as a result, should excite the higher frequencies of the impulse much more than the titanium club. The greater thickness of the steel club provides additional stiffness. So, from just a material’s perspective the loss of hearing should be greater for a steel club.
6. The coefficient of restitution (COR) is used to measure the elasticity or efficiency of energy transfer between a golf ball and club head. The United States Golf Association, in conjunction with the Royal and Ancient, St. Andrews, Scotland, stipulates that the upper limit of COR for clubs used in competition is 0.83.3.{{4}} [[4]] United States Golf Association. Rules of golf 2008.[[4]] Some have interpreted this to mean that a club head striking a ball at 100 mph will cause the ball to travel at 83 mph. Thinner-faced titanium clubs are said to have a greater COR and as a result, deform on impact more easily, resulting in the so-called trampoline effect. This has been an explanation for not only propelling the ball further, but resulting in a louder noise.
Sounds simple and straightforward, right? Peter Hart of the Glasgow Royal Infirmary felt compelled to comment on the COR.{{5}} [[5]] Coefficient of restitution. Replies to: Is golf bad for your hearing. British Medical Journal. Sport. Dec. 29, 2008, Feb 9, 2009. http://www.bmj.com/content/337/bmj.a2835.extract/reply.[[5]] He stated that if what was said in the previous paragraph were true the club head would have to either pass through the ball, or decelerate quite substantially to less than the ball’s speed, resulting in a very nasty kickback to the golfer’s arms. In fact the coefficient of restitution is calculated by (V2f – V1f)/(V1 – V2) where V1 and V2 are the scalar velocities of the two colliding objects (here, the club head and ball) before impact, and V1f and V2f are the velocities of the respective objects after impact. Using this formula they found that a golf club head with a coefficient of 0.83, traveling at 100 mph, will impart a velocity of 183 mph to a golf ball, assuming zero deceleration of the golf club at impact (which is fairly safe where one object far outweighs the other).
7. How loud were the sounds? Studies conducted by Ellis at the University of Derby found that although the thin-faced titanium golf clubs can produce sound levels nearly twice as loud as traditional clubs when a ball is hit, using any club tested in the British Medical Journal is unlikely to excel legal levels.{{6}} [[6]] Titanium golf clubs twice as loud as steel clubs. http://www.telegraph.co.uk/news/uknews/6244497/Titanium-golf-clubs-twice-as-loud-as-steel-clubs.html.[[6]] First, golfers would have to hit more than 1,000 balls in a single session to exceed damage risk criteria for impulse noises.{{7}} [[7]] National Institute for Occupational Safety and Health. Occupational Noise Exposure: Revised Criteria 1998, page 25.[[7]] Ellis recorded noise levels of golfers hitting balls on a driving range with a variety of clubs. Single event level noise readings ranged from 86 dB to 94 dB SPL. And, interestingly, certain clubs appeared to make more noise in an amateur’s hands, but others more noise in a professional’s hands using the same clubs. Additionally, wind and damping of the area surrounding the shot have a significant influence on the overall SPL at the ear.
Mr. Ellis’s average SPL noise readings for each club, when hit by a professional golfer were as follows:
- New titanium club – 94dB
- New titanium club – 94dB
- New titanium club – 93dB
- A slightly older modern club (titanium) 93dB
- A club ten years old (titanium) 87dB
- A modern steel-headed driver 86dB
- A five iron golf club 79dB
- A five iron golf club 79dB
8. Because of the levels measured, some have suggested the wearing of earplugs when playing golf. However, it is known that participants in almost every sport rely on the sound feedback to know how their equipment is performing and also to gauge the events around them, so this might not be very acceptable (possibly with the exception of the sound of the “splash” when water is encountered). On the other hand, when faced with a choice of being killed by an errant golf shot (not hearing a golfer yelling “fore” or of being run over by a golf cart that was not heard) or of “possibly” losing some hearing because of not wearing earplugs while hitting a golf ball, the decision may not be difficult to make.
Summary: Score Card:
- Initial sensationalism based on theory and one patient = Numerous reports and publicity
- Legitimate followup questions and data = No publicity
Blogger’s summary: Yes, theory sometimes does get in the way of reality.
