Abstract
Objective
To compare hearing thresholds at 250 and 500 Hz in pediatric patients with tympanic membrane perforations (TMP) using RadioEar IP30 insert earphones and RadioEar TDH50s 3045 supra‐aural headphones
Study Design
Prospective clinical pilot study.
Setting
Primary Children's Hospital, Utah.
Methods
Children (<18 years of age) were prospectively enrolled into 2 groups based on the presence of TMPs (no TMP, TMP). Hearing thresholds were measured at 250 and 500 Hz using RadioEar IP30 insert earphones and RadioEar TDH50s 3045 supra‐aural headphones for all participants.
Results
At 250 and 500 Hz, hearing thresholds were significantly higher when recorded with insert earphones than with supra‐aural headphones in pediatric participants with TMPs. At 250 Hz, thresholds obtained with inserts were 14.7 ± 7.2 dB (P < .001) higher than thresholds obtained with supra‐aural headphones and 8.0 ± 7.5 dB higher (P < .01) at 500 Hz.
Conclusion
Low‐frequency hearing thresholds were significantly higher when measured with insert earphones in patients with TMPsbut not in patients without TMPs. A diagnosis of low‐frequency hearing loss must be interpreted with caution when using insert earphones in participants with TMPs.
Keywords: insert earphones, low‐frequency hearing thresholds, pediatric, supra‐aural headphones, transducers, tympanic membrane perforation
For pediatric hearing assessments, insert‐style earphones have become commonly used for pure‐tone audiometry. 1 , 2 , 3 Advantages of insert earphones include a reduction of ambient noise, increased interaural attenuation, and the reduced need to present masking noise to the nontest ear. 2 , 3 , 4 , 5 Previous research in patients with normal hearing has suggested that there is no significant difference in speech recognition thresholds or pure‐tone thresholds between insert earphones and supra‐aural headphones. 5 , 6 However, sound pressures administered by transducers may change depending on transducer type, the volume of the middle ear, and the frequency. 7 Therefore, in patients with a middle ear abnormality, there may be a significant difference in hearing thresholds obtained by different transducers. Knowing which instruments are more accurate and reliable allows audiologists and otologists to interpret audiologic exams more accurately, understand hearing‐related issues, and improve treatment.
Voss et al found that middle ear pathology, such as mastoid bowls or tympanostomy tubes, decreases sound pressures by 5 to 35 dB when administered by insert earphones at frequencies below 1000 Hz. 7 Decreased sound pressures further lead to an exaggerated measured hearing loss. 7 These findings are consistent with that found by Tokar‐Prejna and Meinzen‐Derr, in which insert earphones overestimated hearing loss in children with ventilation tubes. 8 In another paper by Voss et al, they reported that sound pressure levels of supra‐aural headphones are minimally affected by ear canal dimensions, whereas changes in both ear dimensions and impedance at the tympanic membrane affect the sound pressure levels of insert earphones. 9 Therefore, compared to insert earphones, ear‐canal pressures produced by supra‐aural headphones are less affected by tympanic membrane perforations (TMPs). 7 Furthermore, tympanic membrane perforations can greatly reduce the impedance from an insert earphone's small external‐ear volume. 10 As the ear's impedance magnitude decreases, ear‐canal pressure also decreases, which results in the false presence of mild, low‐frequency hearing loss.
We found only 1 paper by Voss et al directly measuring low‐frequency hearing thresholds by transducer type in ears with TMPs. 7 However, only 5 adult subjects were evaluated. The objective of this study was to determine the preliminary effect of transducer type on low‐frequency hearing loss in pediatric patients with tympanic membrane perforations. We hypothesized that insert earphones would result in higher low‐frequency thresholds than those measured with supra‐aural headphones in children with tympanic membrane perforations.
Methods
Participants
Children (from age 4 to under the age of 18; mean ± SD 11.0 ± 4.2 year) receiving an audiological examination and children with an otologic exam indicating a tympanic membrane perforation in at least one ear were eligible for this study. Children with normal bilateral tympanic membranes receiving an audiological examination were eligible for being in the control group. The exclusion criteria were presence of active or chronic middle ear disease, sensorineural hearing loss or conductive hearing loss, or a history of middle ear surgery.
Participants were stratified into 2 groups by the presence of a tympanic membrane perforation: the control group had no perforation and the experimental group had perforations.
Procedure
An audiological examination using conventional audiometry methods was performed with RadioEar IP30 insert earphones and RadioEar TDH50s 3045 headphones at 250 and 500 Hz for all participants, including patients with normal bilateral tympanic membranes and patients with TMPs. The step size of the attenuator of the audiometer was 5 dB, and audiometric thresholds were recorded in dB HL. Only those with reliable individual hearing thresholds at these frequencies were included in this study.
Statistical Analysis
To measure the effect of transducers, mean thresholds using insert earphones were compared to the mean thresholds using supra‐aural headphones for each ear. Differences between inserts and headphone measurements were determined using Mann‐Whitney test (nonparametric) for those with tympanic membrane perforations and those without. Differences in hearing thresholds between ears with and without tympanic membrane perforations were also compared using Mann‐Whitney tests (nonparametric). Values were presented as mean and standard deviation.
Ethical Considerations
The study was approved by the University of Utah Institutional Review Board (IRB_00133824), and informed consent was obtained from all participants and/or their parents.
Results
Subject Characteristics
As shown in Figure 1, of the 30 participants, 13 had a unilateral TMP and 1 had a bilateral TMP. The group without TMPs consisted of 21 ears from 16 children. The mean age for children without TMPs was 11.6 ± 3.6 years and for children with TMPs was 10.3 ± 5.0 years, with no significant age difference between the 2 groups by a Mann‐Whitney test (P = .34). Of the children with tympanic membrane perforations, 8 (53%) were male, whereas among children without TMPs, 12 (57%) were male. There was no significant difference in sex among all groups (P = .71) by Fischer's exact test. Characteristics of participants are shown in Table 1.
Figure 1.
Flow chart of study participants.
Table 1.
Subject Characteristics and Thresholds (dB) for Headphones and Insert Earphones in Each of the TMP Conditions
| Characteristics | No TMP (N = 21 ears) | Any TMP (N = 15 ears) |
|---|---|---|
| Male child, N (%) | 12 (57%) | 8 (53%) |
| Mean age in years ± SD | 11.6 ± 3.6 | 10.7 ± 4.9 |
| Mean insert threshold (dB HL) at 250 Hz ±SD | 15.5 ± 6.5b | 41.4 ± 11.4a , b |
| Mean headphone threshold (dB) at 250 Hz ±SD | 12.4 ± 5.4b | 26.7 ± 10.6a , b |
| Mean insert threshold (dB) at 500 Hz ±SD | 13.6 ± 4.8b | 32.0 ± 12.9a , b |
| Mean headphone threshold (dB) at 500 Hz ±SD | 11.2 ± 6.1b | 24.0 ± 12.1a , b |
Comparison of low‐frequency thresholds measured by insert earphones and headphones (P < .05).
Comparison between ears with and without tympanic membrane perforation groups found significant (P < .05).
Results of Data Analysis
As shown in Figure 2, hearing thresholds at 250 and 500 Hz for ears with TMPs were significantly higher when measured with insert earphones than with supra‐aural headphones. At 250 Hz, the mean ± SD hearing threshold for inserts was 41.3 ± 11.4 dB HL and for supra‐aural headphones was 26.7 ± 10.6 dB HL, resulting in a mean difference of 14.7 ± 7.2 dB in ears with tympanic membrane perforations. The Mann‐Whitney test showed a significant difference in the hearing thresholds between these transducers at 250 Hz (P = .002; U = 41.5). The findings at 500 Hz were consistent with the findings at 250 Hz, with a mean difference of 8.0 ± 7.5 dB, and also showing a statistically significant difference in hearing thresholds between the transducers (P = .04; U = 70.5). At 500 Hz, the mean ± SD hearing threshold for inserts was 32.0 ± 12.9 dB HL and for supra‐aural headphones was 24.0 ± 12.1 dB HL.
Figure 2.
Hearing thresholds in ears with TMPs at 250 and 500 Hz are significantly higher (P < .05) when measured with insert earphones than with headphones, but not in ears without TMPs (P > .05). Bars represent the average hearing thresholds of 15 ears with TMPs and 21 ears without TMPs, while error bars represent the standard error of the mean. Statistical comparisons between insert earphones and headphones were conducted using Mann‐Whitney tests.
For ears without a TMP, at 250 Hz, the mean ± SD hearing threshold measured with insert earphones was 15.5 ± 6.5 dB HL and for supra‐aural headphones was 12.4 ± 5.4 dB HL. The mean difference in hearing thresholds at 250 Hz was 3.1 ± 5.6 dB (P = .06; U = 159). At 500 Hz, the mean ± SD hearing threshold for inserts was 13.6 ± 4.8 dB HL and for supra‐aural headphones was 11.2 ± 6.1 dB HL with a mean difference of 2.4 ± 5.8 dB (P = .09; U = 166). These differences were not statistically significantly different using Mann‐Whitney tests.
Furthermore, at both 250 and 500 Hz, the Mann‐Whitney tests comparing hearing thresholds in ears with and without TMPs showed a significant difference when measured by both insert earphones and supra‐aural headphones (at 250 Hz, P = .00006, U = 33; at 500 Hz, P = .04, U = 93.5). As can be seen in Figure 2, ears with TMPs reported higher hearing thresholds than ears without TMP at both frequencies. At 250 Hz, hearing thresholds for ears with TMPs were 41.3 ± 11.4 dB HL when measured by insert earphones and 26.7 ± 10.6 dB HL when measured by headphones, compared to 15.5 ± 6.5 dB HL when measured by insert earphones and 12.4 ± 5.4 dB HL when measured by supra‐aural headphones for ears without TMPs. At 500 Hz, hearing thresholds for ears with TMPs were 32.0 ± 12.9 dB HL when measured by insert earphones and 24.0 ± 12.1 dB HL when measured by headphones, compared to 13.6 ± 4.8 dB HL dB HL when measured by insert earphones and 11.2 ± 6.1 dB HL when measured by supra‐aural headphones for ears without TMPs.
Discussion
In this pilot study, hearing thresholds of patients with tympanic membrane perforations were significantly higher when measured with insert earphones than with supra‐aural headphones at low‐frequency hearing thresholds, suggesting that insert earphones may overestimate hearing loss in patients with tympanic membrane perforations. The use of insert earphones resulted in a 14.7 ± 7.2 dB higher value at 250 Hz and 8.0 ± 7.5 dB higher value at 500 Hz. When comparing low‐frequency hearing thresholds of participants without TMPs, the differences (3.1 dB at 250 Hz; 2.4 dB at 500 Hz) were less than 5 dB, which is within the standard measurement error of pure‐tone threshold measurements, and were not statistically significant. 11 , 12
Voss et al previously found that with insert earphones below 1000 Hz, sound pressures generated in ears with tympanostomy tubes and tympanic membrane perforations were 5 to 25 dB lower compared to sound pressures generated in ears without any middle ear condition. 7 , 13 The generalizability of their results was limited by a small sample size and only included adult participants. Tokar‐Prejna and Meinzen‐Derr demonstrated that insert earphones overestimate hearing loss in children with ventilation tubes by 9 and 14 dB at 250 and 500 Hz when compared to those with headphones. 8 However, they did not evaluate subjects with TMPs. We report that insert earphones show higher thresholds by 8.0 and 14.6 dB in children with tympanic membrane perforations at 250 and 500 Hz. These results suggests that tympanic membrane perforations reduce the sound pressure administered by insert earphones at 250 and 500 Hz. As previously mentioned, Voss et al, described how tympanic membrane perforations can reduce the impedance from an insert earphone's small external‐ear volume. 10 This results in a decrease to ear‐canal pressure and apparent low‐frequency hearing loss. In this pilot study, we have confirmed the effect of the decrease in ear pressure by insert earphones on low‐frequency hearing thresholds.
Our study has several major limitations. The primary limitation is that all data were collected using one brand of audiology equipment and one model of each transducer. As the quality, accuracy, and precision of instruments vary by brand, this greatly limits the generalizability of our results. The data were also obtained from one institution and may not be generalizable to other institutions across the United States. Furthermore, the sample size of the groups is relatively small especially for those with larger TMPs. A larger sample would allow a more robust analysis of hearing thresholds by perforation size. For all these reasons, our results are preliminary and need to be validated by a larger study using multiple brands and models of audiology equipment and with a much larger sample size.
Overall, these findings suggest that hearing thresholds may be slightly incorrectly elevated by 8 and 14 dB when measured with insert earphones at 250 and 500 Hz in ears with tympanic membrane perforations. These measurements may indicate a mild, low‐frequency conductive hearing loss. The use of headphones to test these frequencies is less likely to show elevated thresholds and should be considered when testing children at these lower frequencies. Accurately measuring hearing thresholds is important for audiologists and otologists to assess and treat hearing loss, and the overestimation of low‐frequency hearing loss may lead to unnecessary treatment interventions.
Conclusion
The type of transducer used to administer the sound pressure for audiometric tests may confound the hearing threshold responses in pediatric patients with tympanic membrane perforations. We compared supra‐aural headphones and insert earphones in pediatric patients with and without tympanic membrane perforations. Low‐frequency hearing thresholds were higher when measured with insert earphones, falsely suggesting a greater hearing loss in patients with tympanic membrane perforations. Supra‐aural headphones may be a better approach when testing at frequencies of 250 and 500 Hz in patients with tympanic membrane perforations.
Author Contributions
Anna Hsu, conceptualization, data collection, data analysis, and review and editing of the manuscript; Sarah Hassan AL‐Nemer, data collection and data analysis; Peter Kfoury, data collection and review of the manuscript; Jordan Stout, data collection and review of the manuscript; Anna Holley, data collection; Caitlin Stone, conceptualization, data analysis, and review and editing of the manuscript; Matthew Firpo, conceptualization, data analysis, and review and editing of the manuscript; Albert Park, conceptualization, data collection, data analysis, and review and editing of the manuscript.
Disclosures
Competing interests
None.
Funding source
None.
Acknowledgments
We would like to acknowledge Walid Khalid Salah for his work in writing the IRB that was submitted for this project. We would also like to acknowledge Dr Skylar Jennings for reviewing the manuscript. Since the study has been completed, Dr Caitlin Stone has moved to the Audiology Department at the Children's Hospital of Wisconsin.
This article was presented at the AAO‐HNSF 2023 Annual Meeting & OTO Experience; September 30‐October 4, 2023; Nashville, Tennessee
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