Research Article Impulse Noise: Can Hitting a Softball Harm Your...

Research ArticleImpulse Noise Can Hitting a Softball Harm Your Hearing

Korrine Cook and Samuel R Atcherson

Department of Audiology and Speech Pathology University of Arkansas for Medical SciencesUniversity of Arkansas at Little Rock 2801 South University Avenue Little Rock AR 72204 USA

Correspondence should be addressed to Samuel R Atcherson sratchersonualredu

Received 31 August 2013 Accepted 12 November 2013 Published 20 March 2014

Academic Editors P Clarke S Maune and P OrsquoFlynn

Copyright copy 2014 K Cook and S R AtchersonThis is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited

The purpose of this study is to identify whether or not different materials of softball bats (wooden aluminum and composite)are a potential risk harm to hearing when batting players strike a 1210158401015840 core 40 softball during slow underhand pitch typical ofrecreational games Peak sound pressure level measurements and spectral analyses were conducted for three controlled softballpitches to a batting participant using each of the different bat materials in an unused outdoor playing field with regulation distancesbetween the pitcherrsquos mound and batterrsquos box The results revealed that highest recorded peak sound pressure level was recordedfrom the aluminum (1246 dBC) bat followed by the composite (1212 dBC) and wooden (1200 dBC) bats Spectral analysis revealedcomposite and wooden bats with similar broadly distributed amplitude-frequency response The aluminum bat also produced abroadly distributed amplitude-frequency response but there were also two very distinct peaks at around 1700Hz and 2260Hzabove the noise floor that produced its ringing (or ping) sound after being struck Impulse (transient) sounds less than 140 dBCmay permit multiple exposures and softball bats used in a recreational slow pitch may pose little to no risk to hearing

1 Introduction

Dangerous noise levels in a sporting event such as football(soccer) basketball or baseball could come from crowdnoise referee whistles and sporting equipment Stadiumor indoor area employees who work routinely in theseenvironments can also be at risk of loud noise exposure [1ndash3]National Football League (NFL) games have been measuredto range between 91 and 95 dBA [2] which can have animpact on all individuals involved In indoor hockey arenascollegiate games can reach levels from 81 to 96 dBA whilesemiprofessional games can reach levels from 85 to 97 dBAA study involving two spectators wearing personal noisedosimeters measured at three different 2006 Stanley CupFinal games recorded levels between 100 and 104 dBA [4] Inaddition audiometric testing revealed temporary thresholdshifts of 5 to 10 dB on average but in one participant therewas a 20 dB shift

During any sporting event fans can increase noise levelsby screaming banging on the seats or bleachers and wherepermitted using devices such as thundersticks and vuvuzelasVuvuzelas are trumpet-like instruments capable of producingsound pressure levels between 125 and 130 dB and those

who blow these instruments can have significant distortion-product otoacoustic emission reductions that may lead tohearing loss [5] Fans who blew the vuvuzelas had the greatestexposure followed by nearby fans less than 1 meter fromthe vuvuzela Realistically in any game where vuvuzelas arepermitted there are probably hundreds of fans using thesedevices putting many individuals at risk of hearing loss

Sports officials (referees) who use whistles may be con-tributing to their own hearing loss and other auditory symp-toms such as tinnitus [6] Moreover a single whistle blownby experienced officials was reportedly as high as 116 dBAand the 100 noise exposure dose over repeated blows canbe reached in as little as 5 sec Fortunately whistle blows maynot have the same effect on the players or fans unless they areclose to the sports official

Of recent interest and relevance to the present study astudy of modern golf drivers was conducted to determinepeak levels and potential risk for hearing loss [7] Thisparticular study was motivated by 55-year-old right-handedmale patient who visited an ear nose and throat clinic withcomplaints of tinnitus and reduced hearing in the right earAn audiogram revealed a high frequency hearing loss inboth ears but the right ear had a noise-induced hearing loss

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 702723 4 pageshttpdxdoiorg1011552014702723

2 The Scientific World Journal

configuration that was up to 20 dB HL worse than the leftear at 4 and 6 kHz He reported that he had been playinggolf three times a week with a King Cobra LD titanium cluband owned the golf driver for about 18 months Magneticresonance imaging (MRI) was negative for tumor growthson the auditory nerves Other than playing golf the patientreported that he had no significant exposure to occupationalor recreational noise Thus the investigators designed astudy to compare peak sound pressure levels produced bysix different thick-faced stainless steel golf drivers with sixdifferent thin-faced titaniumgolf drivers Results of this studyshowed that all of the thin-faced titanium drivers producedmore intense sound pressure levels than the stainless steeldrivers on the order of about 10 dB The thin-faced driversproduced levels between 120 and 130 dB however whetherthe measurements were A- or C-weighting was not reportedThese levels potentially put the individual player and nearbygolfing partners at risk of temporary or permanent thresholdshift

The foregoing discussion of sport-related noise exposurefrom crowds officiating equipment or sporting equipmentis pervasive However we were not aware of studies formallyevaluating peak sound pressure levels of softball bats Itis generally well known that aluminum bats produce acharacteristic ldquopingrdquo sound while wooden bats producemoreof a ldquocrackrdquo sound Often times the ldquopingrdquo is perceivedmuch louder dampens less quickly and is heard at furtherdistances For these reasons the present study was designedto measure peak sound levels of three different softballbat materials (wood composite and aluminum) with ballsthrown using a recreational slow pitch This study bearsrelevance to audiologists and otologists who may encounterpatients with noise-induced hearing loss or other auditorysymptoms (eg tinnitus) due to sporting equipment Whenhearing is unprotected from high levels of noise whetherthe noise has a continuous or impulse quality individualsmay present with hearing loss (or other auditory processingproblems [8]) tinnitus and a reduced quality of life [4]Unlike all other hearing loss etiologies hearing loss causedby noise from occupational or recreational activities is 100preventable [9] Noise-induced hearing loss occurs graduallythat many people do not discover the adverse effects of noiseuntil it is too late for reversal

2 Methods

21 Participants In this study a batter participant was taskedto hit softballs using three different softball bats delivered by apitcher participant each with amateur and collegiate softballexperience The same two participants were available on twomeasurement days All procedures received prior approvalby the Human Subjects Review Board at the University ofArkansas at Little Rock (Protocol number 13-058)

22 Materials and Setting Each of the three softball bats hada weight of 265 ounces and length of 32 inches All weremanufactured by Worth (St Louis MO USA) The specificmodels used were Storm (aluminum) Mayhem (composite)

and Mayhem Ash (wood) Unlike wood and aluminum batscomposite bats are the latest technology and can be made outof graphite-fiber composite or have an aluminum core witha graphite lining Core 40 softballs were used in this studyA core 40 softball is considered a low core and does not haveas much ldquobouncerdquo as a core 44 or 47 All measurements wereperformed at an empty community softball complex Soundmeasures were only taken on days when the temperature wasabove 65∘F (183∘C) as temperatures is less than 60∘F (155∘C)degrees can result in damage to the bats

23 Instrumentation and Procedures A sound level meterwith oscilloscope setup was used to capture time domainwaveforms and also record sound level measurements Thesetup included a PC-based laptop with PicoScope softwareand USB-based PicoScope oscilloscope (Tyler TX USA)plugged into the laptop and output of the Bruel amp Kjaeligr Type2250 (Skodsborgvej Denmark) sound level meter coupled tothe PicoScope A Type 4189 1210158401015840 microphone was used tocapture the levels of the bat striking the softball The soundlevel meter was calibrated before all sound measurementsand all recorded peak levels were measured using a C-weighted dB filter Although the A-weighted measurementsare most commonly reported C-weighted peak sound levelsof 140 dB for impulse-type noise are also often reported asthe level that should not be exceeded by some countriesand independent organizations [10] The parameters of thePicoScope were set as follows channel A collection time500msdiv horizontal zoom times1 number of samples 1MSinput range plusmn2 to 5V resolution 8 bits and coupling AC orDC Following timewaveform capture using the oscilloscopethemeasurementwith the highest peak level was converted toa readable WAV file using MATLAB software (Natick MAUSA) to perform spectral analysis using Adobe Audition 20software (San Jose CA USA) The time duration of each ofthese measurements was also recorded

The sound level meter was placed in the opposite batterrsquosbox at a spatial position as close to the height and distance ofthe batterrsquos left ear as possible To obtain reasonable positionthe batter was asked to swing the bat while the height anddistance of the microphone were relative to the home plateThis microphone positioning should give the most accuraterepresentation of the effects of the impulse noise of a bathitting a ball on an individualrsquos hearingminus any head-torsobaffle effect Slow underhand pitches were delivered from thepitcherrsquos mound at regulation distance for softball which is45 feet (137 meters) Three controlled pitches were deliveredfor each material of bat An average for each scenario wastaken after 3 pitches for each bat on each day An overallaverage was later taken for each bat type over the two daysof measurements

3 Results

The peak levels ranged as follows wood = 1131ndash1200 dBC(119872 = 1159) composite = 1141ndash1212 dBC (119872 = 1178) andaluminum = 1202ndash1246 dBC (119872 = 1226) (see Figure 1)

The Scientific World Journal 3

1100

1120

1140

1160

1180

1200

1220

1240

1260

Wood Composite Aluminum

Peak

leve

l (dB

SPL

)lowast

Range1131ndash1200

Range1141ndash1212

Range1202ndash1246

lowastConsistent with calculated volt from Pa to dB SPL values with plusmn05dB

Figure 1 Mean peak levels with standard deviations are shown foreach of the three softball bat materials The range of raw peak levelsis also shown lowastPeak levels are C-weighted measures

As the results show the highest peak level recorded wasfrom the aluminum bat The means of the peak levels fromday 1 of each material are as follows wood = 1137 dB SPLcomposite = 1170 dBC and aluminum = 1228 dBC Themeans of the peak levels from day 2 of each material areas follows wood = 1180 dBC composite 1186 dBC andaluminum = 1223 dBC

All impulse sounds were no more than 0111ms in dura-tion and were submitted to spectral analysis The compositeand wooden bats had a smooth broad spread of energyand were similar to one another On the other hand thealuminum bat produced a spectrum also broad but therewere clear areas of multiple peaks of energy above the noisefloor Two very distinct peaks emerged from the noise flooraround 1700Hz and 2260Hz which coincides with the ldquopingrdquoof the aluminum bat Representative time domain waveformsas well as the spectrum for the highest measured sound levelsfor each bat are shown in Figure 2

4 Discussion

Thepresent study investigated the peak sound pressure levelstime duration and spectra of three different softball batmaterials striking a 40 core softball for potential threatto human hearing None of the levels recorded met orexceeded the 140 dBC ceiling limit for allowable exposure[10] However the high peak impulse levels of all the threebat materials could be a potential hazard for a temporarythreshold shift permanent threshold shift or other relatedsymptoms if this level is met with repeated exposure in asingle game with multiple at-bat opportunities or during abatting practice scenarioThe aluminumbats hold the highestrisk of causing a temporary threshold shift permanentthreshold shift or other related symptoms This situation isnot unlike golfing with thin-faced titanium drivers capable ofproducing peak sound pressure levels of 120 to 130 dB [7]Theldquopingrdquo sound produced by the aluminum bat is of the greatest

0 1000 2000 3000 4000 5000 6000 7000 8000

Mag

nitu

de (d

BFS)

Frequency (Hz)

WoodCompositeAluminum

Wood Composite

0

minus20

minus40

minus60

minus80

minus100

minus120

minus140

sim1700Hzsim2260Hz

Aluminum

Figure 2 Time domain wave forms and spectra The time domainwave forms are shown in black with energy lasting on averagearound 01 seconds As can be seen the aluminum bat wave formshows signs of ldquoringingrdquo beyond the initial impulse The spectraof the three highest bat measurements are shown in blue (wood)red (composite) and green (aluminum) Although all three batspectra are broad in nature the aluminum bat has somewhat higherenergy between 4000 and 8000Hz and the two distinct peaks atapproximately 1700 and 2260Hz are shownThese peaks are at least20 dB above the rest of the broadband energy (noise floor)

suspect Spectral analysis with the aluminum bat revealedtwo significant peaks around 1700Hz and 2260Hz which arecomparable to baseball bat data reported by Russell [11] Heshowed a comparison between wooden and aluminum batsand found a very similar distinctive ldquopingrdquo of the aluminumbat producing spectral peaks around 2200 and 2800HzRussellrsquos data as well as the data reported in this present studysuggest that aluminum bats share a common characteristicproducing spectral peaks that emerge between 1500 and3000Hz due to a ringing or ldquotrampoline effectrdquo of the batMoreover these spectral peaks can rise 15 dB or more abovethe noise floor and could target specific cochlear regions Ina given game with few at-bat chances the risk to hearingis low However seasonal batting practice in an enclosedreverberant room or golf driver practice at a driving rangemay well resemble firing guns at a shooting range

Batting practice facilities are known to have a highreverberant acoustical quality They usually have concreteflooring and are in sheet metal or exposed concrete blockbuildingsThis environment can become very loud over timeand increasingly louder with larger groups of batters hittingduring the same practice session In a practice type setting atypical batter could easily hit 100 to 150 balls in one sessionMoreover a single batting sessionmay take about 1 or 2 hoursand maximum allowable doses may be reached faster thanexpected


The present study can only be generalized to recreationalsoftball with slow underhand pitch It is assumed that peaksound pressure levels are higher with faster underhandsoftball pitches and faster overhand baseball pitches Whilewe used a live pitcher with a controlled slow underhandpitch future research on other pitch speeds could be exploredas well as the use of a pitching machine In summary slowunderhand softball pitches most likely pose little to no riskto hearing but batting practice with multiple impulse soundexposures could put an individual at risk of temporary topermanent threshold shift with bat materials that producehigh intensity soundsHearing protection during long battingpractice sessions may be recommended

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] M J Balmer A M Lane A M Nevill and P Ward ldquoInfluenceof crowd noise on soccermdashrefereeing consistency in soccerrdquoJournal of Sport Behavior vol 30 no 2 pp 130ndash145 2007

[2] D J Engard D R Sandfort R W Gotshall and W J BrazileldquoNoise exposure characterization and comparison of threefootball stadiumsrdquo Journal of Occupational and EnvironmentalHygiene vol 7 no 11 pp 616ndash621 2010

[3] C J Cranston W J Brazile D R Sandfort and R W GotshallldquoOccupational and recreational noise exposure from indoorarena hockey gamesrdquo Journal of Occupational and Environmen-tal Hygiene vol 10 pp 11ndash16 2013

[4] W E Hodgetts and R Liu ldquoCan hockey playoffs harm yourhearingrdquoCanadianMedical Association Journal vol 175 no 12pp 1541ndash1542 2006

[5] L Ramma L Petersen and S Singh ldquoVuvuzelas at SouthAfrican soccer matches risks for spectatorrsquos hearingrdquoNoise andHealth vol 13 no 50 pp 71ndash75 2011

[6] G A Flamme and NWilliams ldquoSports officialsrsquo hearing statuswhistle use as a factor contributing to hearing troublerdquo Journalof Occupational and Environmental Hygiene vol 10 no 1 pp1ndash10 2013

[7] M A Buchanan P R Wilkinson and J E Fitzgerald ldquoIs golfbad for your hearingrdquo British Medical Journal vol 337 ArticleID a2835 pp 1437ndash1438 2008

[8] B A Bohne and G W Harding ldquoNoise induced hearing lossrdquo1999 httpoto2wustledubbearsnoisehtm

[9] P M Rabinowitz ldquoNoise-induced hearing lossrdquo AmericanFamily Physician vol 61 no 9 pp 2749ndash2756 2000

[10] J Starck E Toppila and I Pyykko ldquoImpulse noise and riskcriteriardquo Noise and Health vol 5 no 20 pp 63ndash73 2003

[11] D A Russell ldquolsquoCrackrsquo vs ldquopingrdquo (comparing wood and alu-minum bats)rdquo Physics and Acoustic of Baseball and SoftballBats 2003 httpwwwacspsuedudrussellbatscrack-pinghtml

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


configuration that was up to 20 dB HL worse than the leftear at 4 and 6 kHz He reported that he had been playinggolf three times a week with a King Cobra LD titanium cluband owned the golf driver for about 18 months Magneticresonance imaging (MRI) was negative for tumor growthson the auditory nerves Other than playing golf the patientreported that he had no significant exposure to occupationalor recreational noise Thus the investigators designed astudy to compare peak sound pressure levels produced bysix different thick-faced stainless steel golf drivers with sixdifferent thin-faced titaniumgolf drivers Results of this studyshowed that all of the thin-faced titanium drivers producedmore intense sound pressure levels than the stainless steeldrivers on the order of about 10 dB The thin-faced driversproduced levels between 120 and 130 dB however whetherthe measurements were A- or C-weighting was not reportedThese levels potentially put the individual player and nearbygolfing partners at risk of temporary or permanent thresholdshift

The foregoing discussion of sport-related noise exposurefrom crowds officiating equipment or sporting equipmentis pervasive However we were not aware of studies formallyevaluating peak sound pressure levels of softball bats Itis generally well known that aluminum bats produce acharacteristic ldquopingrdquo sound while wooden bats producemoreof a ldquocrackrdquo sound Often times the ldquopingrdquo is perceivedmuch louder dampens less quickly and is heard at furtherdistances For these reasons the present study was designedto measure peak sound levels of three different softballbat materials (wood composite and aluminum) with ballsthrown using a recreational slow pitch This study bearsrelevance to audiologists and otologists who may encounterpatients with noise-induced hearing loss or other auditorysymptoms (eg tinnitus) due to sporting equipment Whenhearing is unprotected from high levels of noise whetherthe noise has a continuous or impulse quality individualsmay present with hearing loss (or other auditory processingproblems [8]) tinnitus and a reduced quality of life [4]Unlike all other hearing loss etiologies hearing loss causedby noise from occupational or recreational activities is 100preventable [9] Noise-induced hearing loss occurs graduallythat many people do not discover the adverse effects of noiseuntil it is too late for reversal

2 Methods

21 Participants In this study a batter participant was taskedto hit softballs using three different softball bats delivered by apitcher participant each with amateur and collegiate softballexperience The same two participants were available on twomeasurement days All procedures received prior approvalby the Human Subjects Review Board at the University ofArkansas at Little Rock (Protocol number 13-058)

22 Materials and Setting Each of the three softball bats hada weight of 265 ounces and length of 32 inches All weremanufactured by Worth (St Louis MO USA) The specificmodels used were Storm (aluminum) Mayhem (composite)

and Mayhem Ash (wood) Unlike wood and aluminum batscomposite bats are the latest technology and can be made outof graphite-fiber composite or have an aluminum core witha graphite lining Core 40 softballs were used in this studyA core 40 softball is considered a low core and does not haveas much ldquobouncerdquo as a core 44 or 47 All measurements wereperformed at an empty community softball complex Soundmeasures were only taken on days when the temperature wasabove 65∘F (183∘C) as temperatures is less than 60∘F (155∘C)degrees can result in damage to the bats

23 Instrumentation and Procedures A sound level meterwith oscilloscope setup was used to capture time domainwaveforms and also record sound level measurements Thesetup included a PC-based laptop with PicoScope softwareand USB-based PicoScope oscilloscope (Tyler TX USA)plugged into the laptop and output of the Bruel amp Kjaeligr Type2250 (Skodsborgvej Denmark) sound level meter coupled tothe PicoScope A Type 4189 1210158401015840 microphone was used tocapture the levels of the bat striking the softball The soundlevel meter was calibrated before all sound measurementsand all recorded peak levels were measured using a C-weighted dB filter Although the A-weighted measurementsare most commonly reported C-weighted peak sound levelsof 140 dB for impulse-type noise are also often reported asthe level that should not be exceeded by some countriesand independent organizations [10] The parameters of thePicoScope were set as follows channel A collection time500msdiv horizontal zoom times1 number of samples 1MSinput range plusmn2 to 5V resolution 8 bits and coupling AC orDC Following timewaveform capture using the oscilloscopethemeasurementwith the highest peak level was converted toa readable WAV file using MATLAB software (Natick MAUSA) to perform spectral analysis using Adobe Audition 20software (San Jose CA USA) The time duration of each ofthese measurements was also recorded

The sound level meter was placed in the opposite batterrsquosbox at a spatial position as close to the height and distance ofthe batterrsquos left ear as possible To obtain reasonable positionthe batter was asked to swing the bat while the height anddistance of the microphone were relative to the home plateThis microphone positioning should give the most accuraterepresentation of the effects of the impulse noise of a bathitting a ball on an individualrsquos hearingminus any head-torsobaffle effect Slow underhand pitches were delivered from thepitcherrsquos mound at regulation distance for softball which is45 feet (137 meters) Three controlled pitches were deliveredfor each material of bat An average for each scenario wastaken after 3 pitches for each bat on each day An overallaverage was later taken for each bat type over the two daysof measurements

3 Results

The peak levels ranged as follows wood = 1131ndash1200 dBC(119872 = 1159) composite = 1141ndash1212 dBC (119872 = 1178) andaluminum = 1202ndash1246 dBC (119872 = 1226) (see Figure 1)


1100

1120

1140

1160

1180

1200

1220

1240

1260


Peak

leve

l (dB

SPL

)lowast

Range1131ndash1200

Range1141ndash1212

Range1202ndash1246





4 Discussion


0 1000 2000 3000 4000 5000 6000 7000 8000

Mag

nitu

de (d

BFS)

Frequency (Hz)


Wood Composite

0

minus20

minus40

minus60

minus80

minus100

minus120

minus140

sim1700Hzsim2260Hz

Aluminum








References

















of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















1100

1120

1140

1160

1180

1200

1220

1240

1260


Peak

leve

l (dB

SPL

)lowast

Range1131ndash1200

Range1141ndash1212

Range1202ndash1246





4 Discussion


0 1000 2000 3000 4000 5000 6000 7000 8000

Mag

nitu

de (d

BFS)

Frequency (Hz)


Wood Composite

0

minus20

minus40

minus60

minus80

minus100

minus120

minus140

sim1700Hzsim2260Hz

Aluminum








References

















of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















References

















of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





















of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















Research Article Impulse Noise: Can Hitting a Softball Harm Your...

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