Download Effect of do-it-yourself custom-molded earplugs on REAT compared

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
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30
20
10
RESEARCH POSTER PRESENTATION DESIGN © 2011
www.PosterPresentations.com
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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.