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Effect of do-it-yourself custom-molded earplugs on REAT compared to traditional HPDs Evan Mattice, B.S. & Ross Roeser, Ph.D. Background Purpose Previous studies have revealed an overestimation of the effect of hearing protection devices, though these studies focus on conventional HPDs such as earmuffs, foam, flange, and professionally-fit custom-molded earplugs. Currently there is no evidence of the efficacy of do-it-yourself custommolded earplugs. This study aimed to determine the effect of do-it-yourself custom-molded earplugs, created by naïve, untrained adults, on real ear attenuation at threshold (REAT) as compared to conventional earplugs with the same noise reduction rating. Sample Figure 1. a) Radians Do-It-Yourself Custom Molded Earplug; b) Howard Leight Quiet Reusable Foam Earplug; c) Peltor Next Tri-Flange Reusable Ear Plug a) b) c) Unoccluded thresholds were obtained over an extended number of one-third octave bands with center frequencies at 125 Hz, 250 Hz, 5000 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 6 kHz, and 8 kHz. Stimuli were presented in soundfield via loudspeaker positioned 1 meter from the participant at 0 degrees azimuth. Participants created custom-molded earplugs by following instructions included in the Radians earplug kit. Following completion of the custom-molded earplugs, occluded thresholds were obtained in the exact manner that unoccluded thresholds were obtained. These measures were completed in succession for all three types of earplugs and the order was counterbalanced to control for order effects. subjects followed manufacturer's HPD instructions under supervision. Results Mean REAT at each threshold for all 12 participants for the do-it-yourself custom-molded, foam, and flange HPDs can be found in Table 1 and Figure 2. Mean REAT at each frequency was also compared to the assumed protection value reported by the manufacture for each hearing protection device (Figure 3). A two-way ANOVA was performed, revealing a main effect of frequency (P<0.001) and hearing protection device (P<0.001). Post hoc analysis suggested significant differences between low and high frequency attenuation within HPD, but no significant differences were found across HPD, suggesting that the HPDs do not provide significantly different attenuation at any frequency. MEAN REAT FOR ALL HPDS DIY CUSTOM FOAM FLANGE 125 Hz 250 Hz DIY Custom 15.00 16.25 SD (9.77) (8.56) SE (2.82) (2.47) Foam 10.00 9.17 SD (12.25) (11.25) SE (3.54) (3.25) Flange 12.50 10.83 SD (11.58) (11.24) SE (3.34) (3.25) 40 35 30 25 20 15 10 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz 6000 Hz 8000 Hz FREQUENCY Figure 2. Comparison of mean real ear attenuation at threshold (dB HL) of do-ityourself custom, foam, and flange HPDs per frequency (Hz). Error bars represent standard error. Mean Attenuation Do-It-Yourself Custom Molded Earplugs 40 30 20 10 RESEARCH POSTER PRESENTATION DESIGN © 2011 www.PosterPresentations.com 40 30 20 10 Limitations/Future Directions A sample size of 12 is a limiting factor in measuring the effect of HPD's on REAT. A larger sample will be used in future studies examining the effects of do-it-yourself custom molded hearing protection, which would potentially control for the large amount of variance in this study. Additionally, pre and post training REAT will be used to help determine the effect of training on the use of traditional HPDs and the creation of custom-molded earplugs. References Alam, N., Sinha, V., Jalvi, R., Gurnani, D., Barot, D., & Suryanarayan, A. (2013). Comparative study of attenuation measurement of hearing protection devices by real ear attenuation at threshold method. Indian Journal of Otology, 19(3), 127-127. Retrieved March 9, 2015. Kimball, S. (2008). Making earmold impressions at home: How well can untrained consumers do it? The Hearing Journal, 61(4), 26-30. Retrieved March 9, 2015. U.S. Department of Health and Human Servies: National Institute on Deafness and Other Communication Disorders (2014). Noise-Induced Hearing Loss. NIDCD Fact Sheet: Hearing and Balance. Contact Evan Mattice, B.S. Doctor of Audiology Student at The University of Texas at Dallas [email protected] 40 30 20 10 0 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz 6000 Hz 8000 Hz 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz 6000 Hz 8000 Hz Frequency Frequency PARTICIPANT Mean Attenuation Flange Earplugs c) 1. Although not statistically significant, the do-it-yourself custom-molded earplugs provided a greater mean attenuation than the other two HPDs at all frequencies. 2. There was a large amount of variability in the amount of attenuation provided by each of the HPDs. However, variation as illustrated by standard deviation was lower in the do-it-yourself custom-molded condition in six of the nine tested frequencies (Table 1). 3. None of the HPDs met manufacturer assumed protection values at any frequency, though the do-it-yourself custommolded earplug was closest with high frequency difference in attenuation of less than 10 dB. 50 0 0 MANUFACTURER SPECIFICATIONS Participants were recruited via word of mouth and social media. The project was approved by the Institutional Review Board at The University of Texas at Dallas (IRB # 15-59) Mean Attenuation Foam Earplugs 50 Attenuation (dB) 50 b) Attenuation (dB) a) Attenuation (dB) Participants met the following inclusion criteria: 1. Pure tone threshold sensitivity within normal limits (less than 25 dB HL .25 kHz – 8 kHz); 2. Inter-aural difference in threshold of less than 10 dB HL from .25 kHz – 8 kHz. 3. Normal middle ear function, verified by tympanometry and acoustic reflex; 4. No recent middle-ear pathology per subject report; and 5. No previous formal training in the use of hearing protection 500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz 6000 Hz 8000 Hz 13.75 17.92 28.33 27.92 35.00 33.33 28.33 (8.01) (6.89) (9.85) (11.37) (15.37) (14.97) (9.61) (2.31) (1.99) (2.84) (3.28) (4.44) (4.32) (2.77) 10.42 12.08 20.83 21.25 27.92 26.67 20.83 (11.37) (14.53) (12.02) (10.69) (14.84) (13.71) (17.94) (3.28) (4.19) (3.47) (3.08) (4.28) (3.96) (5.18) 11.25 15.00 22.92 22.92 24.17 23.75 20.83 (13.51) (13.14) (9.88) (8.10) (8.48) (13.67) (16.49) (3.90) (3.79) (2.85) (2.34) (2.45) (3.95) (4.76) Table 1. Mean attenuation per frequency (dB) for each earplug condition. SD= standard deviation SE = standard error. 5 0 Twelve adult subjects (6 male, 6 female) with a mean age of 26.17 (SD = 2.72) were recruited for this study. Conclusions Materials included three types of hearing protection devices (Figure 1): ATTENUATION (DB) According to the National Institute on Deafness and other Communication Disorders (NIDCD), upwards of 26 million Americans ages 20-69 have hearing loss that may be attributed to excessive noise exposure. Fortunately, the solution for reducing this problem relies solely on strategies such as education of potential sources of dangerous noise, avoiding excessive noise when possible, and using hearing protection when avoidance is not manageable (Alam et al., 2013). Consumers have access to an enormous catalog of hearing protection devices thanks to internet purchasing abilities (Kimball, 2008). Generally, standard premolded or moldable hearing protection is most commonly purchased, however there has been a recent uptake in the availability of do-it-yourself custom-molded hearing protection devices (HPDs). These less-expensive custom options may be attractive to individuals exposed to occupational or recreational noise, but it is important to know whether the devices are being properly fit. Previous studies have found that amateurs failed to make proper earmold impressions (Kimball, 2008). If the devices are not being properly fit, individuals may be putting themselves at risk for permanent hearing damage. Methods MANUFACTURER SPECIFICATIONS 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz 6000 Hz 8000 Hz Frequency PARTICIPANT MANUFACTURER SPECIFICATIONS PARTICIPANT Figure 3. a) Assumed mean attenuation (dB) reported by manufacturer per frequency (Hz) compared to mean real ear attenuation at threshold measured in participants for Do-ItYourself Custom Molded (a), Foam (b), and Flange (c) hearing protection devices.