This paper presents reference equivalent threshold sound pressure levels (RETSPLs) for the Wireless Automated Hearing Test System (WAHTS), a recently commercialized device developed for use as a boothless audiometer. Two initial studies were conducted following the ISO 389-9 standard [ISO 389-9 (2009). “Acoustics—Reference zero for the calibration of audiometric equipment. Part 9: Preferred test conditions for the determinations of reference hearing threshold levels” (International Organization for Standardization, Geneva)]. Although the standard recruitment criteria are intended to yield otologically normal test subjects, the recruited populations appeared to have slightly elevated thresholds [5–10 dB hearing level (HL)]. Comparison of WAHTS thresholds to other clinical audiometric equipment revealed bias errors that were consistent with the elevated thresholds of the RETSPL populations. As the objective of RETSPLs is to ensure consistent thresholds regardless of the equipment, this paper presents the RETSPLs initially obtained following ISO 389-9:2009 and suggested correction to account for the elevated HLs of the originally recruited populations. Two additional independent studies demonstrate the validity of these corrected thresholds.

Presently, 14.1% (27.7 × 106) of American adults aged 20–69 years old have unilateral or bilateral hearing impairment that impacts speech understanding and communication (Hoffman et al., 2017). Untreated hearing loss gives rise to a poorer quality of life and increased symptoms of depression (Chia et al., 2007; Dawes et al., 2015; Vannson et al., 2015). For children, hearing loss negatively impacts speech language development (Bess et al., 1998; Needleman, 1977; Tomblin et al., 2015; Yoshinaga-Itano et al., 1998) and psychosocial behavior (Davis et al., 1986). Unilateral hearing loss is associated with increased rates of grade failures, the need for additional educational assistance, speech language delays, fatigue, and emotional/behavioral issues in the classroom (Hornsby et al., 2017; Lieu, 2004; Stevenson et al., 2015). On the other end of the lifespan, research has shown hearing loss is independently associated with accelerated cognitive decline and impairment in older adults (Lin et al., 2013).

Many forms of hearing loss are treatable medically or addressable with technology (e.g., hearing aids), however, many individuals do not receive treatment. Poor access to hearing healthcare is one of the leading factors that may prevent individuals from receiving the benefit of treatment, including a lack of access to diagnostic quality testing. A major barrier to accurate, diagnostic quality hearing tests is the need for expensive infrastructure, specifically, sound-proofed booths and audiologists with specialized training in conducting exams. Furthermore, while there are a number of potential pharmaceutical treatments to either treat or prevent hearing loss currently in development, the ability to evaluate changes in hearing throughout a clinical trial can be challenging precisely because accurate hearing testing requires access to specific infrastructure. Similarly, while ototoxicity monitoring is highly recommended for a number of cancer or other disease treatments, few clinical programs routinely test their patients because of the added burden of a visit to an audiologist with a sound-treated booth (Brungart et al., 2018; Konrad-Martin et al., 2018). To address these issues, new boothless solutions have recently emerged (Gates et al., 2021; Konrad-Martin et al., 2021; Swanepoel et al., 2015; Thompson et al., 2015). One of them is the Wireless Automated Hearing Test System (WAHTS), which was designed to provide high ambient noise attenuation, especially at the lower and mid-frequencies. The need for a boothless solution that provides high ambient noise attenuation has become all the more acute now that the World Health Organization has classified all thresholds at 20 dB hearing level (HL) and above as indicators of hearing loss (Chadha et al., 2021).

The WAHTS has large circumaural ear cups (Fig. 1) that provide isolation from unwanted noise and is on par with single-walled sound booths (Brungart et al., 2018). Additionally, the large ear cups have enough room to house the entire audiometer electronics inside along with the speakers. The right ear cup contains a wireless, audiometer circuit, whereas the left cup contains a rechargeable lithium ion battery. Each ear cup includes a single speaker that connects to the audiometer circuit for sound production. The system communicates through Bluetooth with a mobile device to send commands and receive measurement data. By using the mobile device solely as a user and data interface to the audiometer, the system ensures the calibration and quality of the acoustic stimuli are entirely independent of the mobile device hardware. The WAHTS uses a digital signal processor (DSP) to generate sounds in the ear and run automated algorithms that are saved in its memory. Additional details regarding the WAHTS are provided in Meinke et al. (2017). Because the WAHTS uses its own integrated transducers (the speakers located in the ear cups) that are different than audiometric earphones that come with existing audiometers, it is necessary to establish reference equivalent threshold sound pressure levels (RETSPLs). RETSPLs allow the results for a given transducer to be converted from decibel sound pressure level (dB SPL) measured on a standardized, calibrated ear simulator to the HL (dB HL). By design, the HL reported should be 0 dB HL for individuals with “normal” hearing and allows results to be compared across audiometers and transducers. dB HL is, therefore, a normative scale.

FIG. 1.

(Color online) The WAHTS.

FIG. 1.

(Color online) The WAHTS.

Close modal

ISO-389-9:2009 (ISO, 2009) provides the preferred test protocol for the determination of reference hearing threshold levels for headphones. Subjects are expected to be otologically normal, aged 18–25 years old and with middle ear pressure in the range of ±50 dPa. Subjects are also asked to fill out a questionnaire to rule out noise-induced hearing loss or other past history that could affect hearing. The standard also specifies the frequencies to be used and types of tones. The computation of the RETSPLs is the median of all subjects' thresholds at each frequency in dB SPL as measured on a standardized ear simulator. In contrast, ANSI (2018) only requires stating calibration methods and justifying how RETSPLs were derived.

This article presents results from two independent studies performed to establish the WAHTS RETSPLs according to the ISO-389 method. The results include an additional analysis to correct for the fact that the subjects had elevated thresholds as measured on other commercial audiometers. Finally, in our discussion, we include results of two subsequent studies used to validate the final RETSPL values and demonstrate good agreement with audiometers and transducers currently in use in clinical settings.

RETSPL studies were conducted at two sites: (1) House Clinic (HC) in Los Angeles, CA, USA, and (2) at the National University of Singapore (NUS). Both sites followed the ISO 389-9:2009 standard with regard to evaluating potential subjects for inclusion in the study. In addition to following the ISO standard, threshold measurements were obtained manually at both sites by an audiologist using commercially available clinical audiometers and transducers.

In the HC study, 39 subjects were recruited from the Los Angeles area. The research study was conducted in accordance with an approved local ethical Institutional Review Board (IRB) at the House Clinic, and informed consent was given by all participants.

In the NUS study, 47 subjects were recruited from the NUS community, including students, staff, family members, and friends. All protocols and procedures were approved by the NUS IRB (Reference, B-16-216).

After consenting, subjects were checked for normal otoscopy and tympanometry (type A with a pressure of ± 50 daPA) as defined in ISO 389-9 (ISO, 2009). All subjects then completed a hearing history questionnaire adopted from the standard and reproduced here in the  Appendix. The tester had to probe further if the subjects answered “yes” to some of the questions or had certain types of noise exposure.

Both sites received a WAHTS provided by Creare LLC (Hanover, NH). The WAHTS system (Meinke et al., 2017) came with either a Nexus 7 (ASUS, Taipei, Taiwan) or Tab E (Samsung, Seoul, South Korea) tablet loaded with the open source tablet software, TabSINT, developed by Creare LLC to conduct hearing studies (Shapiro et al., 2020). The WAHTS headset was calibrated on an IEC 60318–1 ear simulator equipped with a type 1 flat plate adapter. The environmental conditions met the ranges specified in ANSI (2018), Appendix C.

For manual threshold measurements, each site used their standard clinical audiometer and transducers. HC used a GSI 61 audiometer (Grason-Stadler, Eden Prairie, MN) with TDH49 (Farmingdale, NY) earphones and NUS used a Siemens Unity audiometer (Sivantos, Singapore, Singapore) with Sennheiser HDA200 headphones (Wedemark, Germany). In both cases, audiometers had been calibrated within less than 1 yr, according to clinical standards for audiometers, and subsequent calibrations showed minimal deviations of 1 dB or less.

For subjects who met inclusion criteria, the audiologist performed manual threshold measurements with the clinical audiometer using a modified Hughson-Westlake procedure (up 5 dB, down 10 dB). At HC, manual thresholds were obtained at all conventional audiometric frequencies up to 8 kHz (0.125, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, and 8 kHz) for 19 of the included subjects. At NUS, manual thresholds were obtained for all of the included subjects and at the same frequencies as HC, plus the extended frequency range up to 16 kHz (9, 10, 11.2, 12.5, 14, and 16 kHz). All of the manual audiometry was performed in a soundproof booth and sound pressure levels (SPLs) met the requirements of ASA/ANSI S3.1-1999 (R2008) (ANSI, 2008) at HC and ISO 8253-1 (ISO, 2010) at NUS.

Both sites used the same WAHTS automated algorithm based on the modified Hughson–Westlake procedure (Carhart and Jerger, 1959) for which details have been reported previously (Meinke et al., 2017). NUS tested in the extended frequency range, whereas HC did not (because of limited time availability of subjects). Subjects were instructed to don the headset themselves, ensuring that their ears were fully covered. Then, they listened to an 8 kHz pulsed tone at 65 dB SPL and were asked to adjust the position of the headphones until the tone sounded the loudest. Subjects then performed automated threshold tests at frequencies between 1 and 8 kHz (specifically, 1, 1.5, 2, 3, 4, 6, and 8 kHz), and then they repeated 1 kHz and proceeded to the extended frequency range (9, 10, 11.2, 12.5, 14, and 16). Finally, they repeated 1 kHz a third time and followed with measurements at 0.75, 0.5, 0.25, and 0.125 kHz. At the end, subjects repeated 1 kHz once more. The repeated tests at 1 kHz were used to ensure reliability. Only the first measurement was used in the RETSPL calculations.

Included at the HC site were 28 subjects (9 males, 19 females) with a mean age of 21.2 ± 2.5 years old (3 subjects were excluded because of their medical history and 7 subjects were excluded because they were not able to complete the full protocol due to time limits). At NUS, 39 subjects were included (19 males and 20 females) with a mean age of 21.3 ± 2.3 years old (8 subjects were excluded due to their medical history or recent noise exposure). Incomplete data were observed in some frequencies because thresholds were outside the range of the WAHTS, usually in the extended frequency range. For thresholds that were beyond the WAHTS limits, a hypothetical value (maximum output level +5 dB) was used to replace the threshold. This is so that the resultant RETSPL values would not be greatly underestimated. This was observed only at 14 and 16 kHz.

The median thresholds in dB SPL were calculated for each population (HC and NUS) and at each frequency. Because of unequal populations, NUS and HC data could not be pooled before taking the median. Instead, the NUS data were randomly down-sampled to the same number of ears as in the HC data, and both data sets were pooled to compute the medians. The down-sampling process was repeated 20 times and each time, new medians were calculated. In the end, the final RETSPLs were computed as the average of the 20 medians at each frequency. The results are shown in Fig. 2 and listed in Table I. The NUS data were analyzed by gender and ear subgroups but revealed no significant differences, a finding that is in agreement with prior studies such as that by Bug and Fedtke (2020).

FIG. 2.

(Color online) The original and adjusted RETSPLs.

FIG. 2.

(Color online) The original and adjusted RETSPLs.

Close modal
TABLE I.

The RETSPLs calculated following the ISO-389 standard and after adjusting for the individuals' hearing thresholds.

Frequency (kHz) 0.125 0.25 0.5 0.75 1 1.5 2 3 4 6 8 9 10 11.2 12.5 14 16
HC  —  20  15  —  10  —  10  10  10  20  25  —  —  —  —  —  — 
NUS  35  25  20  20  15  15  15  10  10  20  20  30  20  20  20  30  60 
ISO-389  35  22  20  20  15  15  14  10  10  20  20  30  20  20  20  30  60 
Adjusted  30  15  10  15  18  25  20  15  25  35  55 
Frequency (kHz) 0.125 0.25 0.5 0.75 1 1.5 2 3 4 6 8 9 10 11.2 12.5 14 16
HC  —  20  15  —  10  —  10  10  10  20  25  —  —  —  —  —  — 
NUS  35  25  20  20  15  15  15  10  10  20  20  30  20  20  20  30  60 
ISO-389  35  22  20  20  15  15  14  10  10  20  20  30  20  20  20  30  60 
Adjusted  30  15  10  15  18  25  20  15  25  35  55 

As described above, thresholds for most subjects were also measured on a separate commercial audiometer. Figure 3 shows the median, 25th and 75th percentiles, minimum and maximum, as well as outliers at each frequency for both populations. An analysis of these data shows that the study populations had median thresholds ranging from +5 dB HL to +10 dB HL at most frequencies and many of the thresholds remained above zero. The spread of thresholds remained relatively stable at 5–10 dB from 125 Hz to 8 kHz, and then increased to a maximum of 25 dB at 16 kHz. The relatively large variability in the extended high frequency range indicates high intersubject threshold variability for normal hearing individuals (see Fig. 4), as also reported in other publications (Jilek et al., 2014; Rodríguez Valiente et al., 2014).

FIG. 3.

The pure tone thresholds at NUS (S) and HC (H) up to 8 kHz. In each box, the central mark ( ) indicates the median, and the bottom and top edges indicate the 25th and 75th percentiles, respectively; the whiskers (the lines extending from the box on both sides) extend to the most extreme data points that are not considered outliers; and the individual markers (+) indicate the outliers.

FIG. 3.

The pure tone thresholds at NUS (S) and HC (H) up to 8 kHz. In each box, the central mark ( ) indicates the median, and the bottom and top edges indicate the 25th and 75th percentiles, respectively; the whiskers (the lines extending from the box on both sides) extend to the most extreme data points that are not considered outliers; and the individual markers (+) indicate the outliers.

Close modal
FIG. 4.

The pure tone thresholds at extended high frequencies at NUS.

FIG. 4.

The pure tone thresholds at extended high frequencies at NUS.

Close modal

To account for threshold medians that were not 0 dB HL and for each ear and each frequency, the WAHTS thresholds measured in SPL were first adjusted by subtracting the thresholds measured with the clinical audiometers. Then, medians were calculated for each population (HC and NUS) and at each frequency. Down-sampling was applied to account for the unequal populations, as in the prior analysis performed according to the ISO 389-9 standard. The adjusted RETSPLs are shown in Fig. 2 and tabulated in Table I. The age distribution is tabulated in Table II.

TABLE II.

The age and gender distribution for the adjusted RETSPL calculations.

Age (yr) 18 19 20 21 22 23 24 25 Unknown
HC male 
HC female 
NUS male  — 
NUS female  10  — 
Age (yr) 18 19 20 21 22 23 24 25 Unknown
HC male 
HC female 
NUS male  — 
NUS female  10  — 

The measurements of thresholds of our study populations with existing, validated equipment, revealed 5–10 dB higher thresholds than would be expected based on the ISO389-9 standard for our two populations. It is difficult to determine specifically why this occured. Most published studies of RETSPLs for other transducers have varied inclusion criteria in addition to those specified in the standard. Han and Poulsen (1998) used an audiometer fitted with a TDH39 (Telephonics, Farmingdale, NY) to obtain baseline audiometric data on all their subjects before measuring the RETSPLs for the Sennheiser HDA200. Their population had a mean threshold within 1 dB of 0 dB HL at all frequencies between 0.250 and 4 kHz. Takeshima et al. (1995) recruited subjects with thresholds below 10 dB HL for frequencies between 0.125 and 8 kHz to measure the RETSPLs of the TDH39P, TDH49P (Telephonics, Farmingdale, NY), HDA200, and NEDO-H3 (Ashida Sound Co., LTD, Tokyo, Japan), although the transducers used to establish the subject thresholds are not specified. More recently, Folkeard et al. (2019) recruited subjects with thresholds 15 dB HL to establish the RETSPLs of the Sennheiser HDA280-CL, whereas Ho et al. (2017) included subjects with thresholds better than 15 dB HL as measured on a clinical audiometer with TDH50 (Telephonics, Farmingdale, NY) headphones, and Smull et al. (2019) recruited subjects with thresholds of 20 dB HL as measured with a clinical audiometer connected to HDA200 transducers to assess the RETSPLs of the HDA280 PRO headphones. It is not entirely clear why the populations recruited in the current studies yielded significant differences in mean and median thresholds as compared to some of these earlier studies. Some of the differences could be due to racial differences because the NUS study recruited subjects from a single race (Asian), whereas the HC population was more diverse, including White, African American, and Asian origins, as well as Hispanic and non-Hispanic ethnicities. It is also possible that some of the populations recruited had higher noise exposure as compared to older studies, even if those exposures did not result in clinically significant hearing loss (Su and Chan, 2017). Another possibility is tester bias during manual audiometry, as suggested by Margolis et al. (2015) in a study that analyzed over 30 000 audiograms from multiple databases and showed manual threshold distributions tended to center at higher levels than automated threshold distributions for similar populations. The authors call it the “good enough bias.” The transducers used to determine the manual thresholds could also impact the results at the higher frequencies because of geometric interactions with the individual subject ears, as has been found previously (Bhatt, 2018; Flamme et al., 2015; Frank, 2001; Han and Poulsen, 1998). However, one important outcome of computing the RETSPLs of a new transducer is to ensure that thresholds measured by different devices are equivalent and can be interpreted in the same way regardless of the measurement system. Ultimately, the dB HL scale was developed to permit comparisons of thresholds across testers, test systems, and possibly even test techniques. To explore the relevance of the results obtained with either approach (ISO or adjusted), two validation studies were conducted using independent populations and test administrators.

Two separate studies were conducted independently to compare the thresholds of individuals obtained with the WAHTS to those obtained in a sound booth with existing commercially available devices. Both of the studies were conducted by researchers who were attempting to validate the use of the WAHTS for future research studies and who, therefore, focused their protocol on the specific methods and frequencies of interest for their studies.

  1. The first study (DT) was conducted at Decibel Therapeutics. In this study, 53 subjects, most with normal hearing, were tested on both ears (106 ears total) once with the WAHTS outside the booth and once within the booth with an Interacoustics Equinox 2.0 audiometer (Middlefart, Denmark) and RadioEar DD450 headphones (Middlefart, Denmark). When testing with the WAHTS, they used an automated method of adjustment (Békésy tracking at a fixed frequency) with a 2 dB step size (see Rieke et al., 2017, for details of the implementation). This was selected because the method offers a smaller step size while maintaining similar time to completion for each threshold. Inside the booth, they used a modified Hughson-Westlake manual audiometry algorithm (10 dB down, 5 dB up). It was expected that the difference in methods would likely yield a slight offset that can be accounted for during analysis (Poling et al., 2016). The thresholds were obtained at 0.125, 0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, 11.2, 12.5, 14, 16, 18, and 20 kHz. The data at 18 and 20 kHz were not included in the comparison because RETSPLs are not available at these frequencies. The thresholds measured in the booth with the reference audiometer are shown in Fig. 5 on the left.

  2. The second study (WR) was conducted in the Hearing Conservation Clinic at the Walter Reed National Military Medical Center. In this study, 173 adult subjects with varied levels of hearing loss were tested on one or both ears (345 ears total) once with the WAHTS outside the sound booth in the Hearing Conservation Clinic waiting room and once with a Defense Occupational and Environmental Health Readiness System-Hearing Conservation (DOEHRS-HC) microprocessor audiometer (CCA 200, Benson Medical, Eden Prairie, MN) and TDH-39 (Telephonics, Farmingdale, NY) headphones. The testing with the WAHTS was completed with an automated modified Hughson-Westlake algorithm, as described previously (Meinke et al., 2017), at 4 kHz. Hearing tested in the DOEHRS-HC booth was completed using an automated Hughson-Westlake method at 4 kHz as well. To reduce the time required for the study, only the 4 kHz thresholds were obtained with the WAHTS for comparison purposes. The testing with the WAHTS and DOEHRS-HC occurred on the same day. The hearing test presented on the WAHTS was performed either directly prior to or immediately after the DOEHRS-HC exam. The order was not randomized but determined, rather, by convenience as subjects were recruited during their visit to the clinic for a hearing test. The thresholds measured with DOEHRS-HC are shown in Fig. 5 on the right.

FIG. 5.

The threshold distribution for subjects from the validation studies conducted at Decibel Therapeutics (left) and Walter Reed (right).

FIG. 5.

The threshold distribution for subjects from the validation studies conducted at Decibel Therapeutics (left) and Walter Reed (right).

Close modal

The data were analyzed by computing the signed difference between the threshold measured with the “reference” audiometer and the threshold measured with the WAHTS. Then, the thresholds from all of the ears were combined to report the mean signed difference in Table III. The data from the DT study were corrected by a factor of +5 dB (added to the WAHTS measurement) at all of the frequencies to account for the difference between the Bekesy-like tracking algorithm (with a smaller, 2 dB step size) and the modified Hughson-Westlake algorithm, as reported in previously published comparisons between the two methods (Poling et al., 2016). These results reveal that at all of the frequencies, the mean signed difference was less than 5 dB when using the adjusted RETSPLs. The mean and standard deviations of the absolute difference between the reference audiometer and the WAHTS was also calculated to reveal any systematic difference between the two devices (Table IV). Figure 6 displays the medians and spread of the signed differences for both validation studies. The medians are all within ±5 dB and no consistent shift is evident, even at the higher frequencies. The standard deviation at 1 kHz for the DT study is relatively large and driven primarily by two outliers (unlike in the original RETSPL studies, DT subjects did not repeat the 1 kHz measurement). The results at frequencies below 8 kHz are consistent with other comparisons between automated and manual audiometry (Swanepoel et al., 2015) or automated and manual audiometry on two different audiometers (Margolis and Moore, 2011), although few studies have compared thresholds measured on two different transducers. Comparison studies recently published tend to focus on the difference in techniques instead, such as automated versus manual measurement (Mahomed et al., 2013; Poling et al., 2016; Swanepoel et al., 2010). Even at the higher frequencies, the median differences are within ±5 dB, although the standard deviations are slightly larger than at the lower frequencies, as has been previously reported (Jilek et al., 2014; Rodríguez Valiente et al., 2014).

TABLE III.

The mean and standard deviation (SD) of the signed difference between reference and WAHTS threshold measurements for each validation study.

Frequency (kHz) 0.125 0.25 0.5 1 2 3 4 6 8 10 11.2 12.5 14 16
DT study mean (dB)  1.4  −2.3  −1.6  −2.7  −4.0  2.1  2.4  −3.4  0.2  1.2  −4.8  1.9  2.1  0.2       
DT study SD (dB)  4.2  3.9  3.3  8.0  3.6  4.3  3.9  6.9  7.4  7.4  6.9  6.3  7.4  6.9       
WR study mean (dB)  —  —  —  —  —  —  0.9  —  —  —  —  —  —  —  —  —  — 
WR study SD (dB)  —  —  —  —  —  —  5.8  —  —  —  —  —  —  —  —  —  — 
Frequency (kHz) 0.125 0.25 0.5 1 2 3 4 6 8 10 11.2 12.5 14 16
DT study mean (dB)  1.4  −2.3  −1.6  −2.7  −4.0  2.1  2.4  −3.4  0.2  1.2  −4.8  1.9  2.1  0.2       
DT study SD (dB)  4.2  3.9  3.3  8.0  3.6  4.3  3.9  6.9  7.4  7.4  6.9  6.3  7.4  6.9       
WR study mean (dB)  —  —  —  —  —  —  0.9  —  —  —  —  —  —  —  —  —  — 
WR study SD (dB)  —  —  —  —  —  —  5.8  —  —  —  —  —  —  —  —  —  — 
TABLE IV.

The mean and standard deviation (SD) of the absolute difference between reference and WAHTS threshold measurements for each validation study.

Frequency (kHz) 0.125 0.25 0.5 1 2 3 4 6 8 10 11.2 12.5 14 16
DT study mean (dB)  3.5  3.7  2.9  4.3  4.5  3.8  3.5  5.6  5.6  5.6  6.5  4.8  5.7  5.3       
DT study SD (dB)  2.8  2.7  2.3  7.4  3.0  2.9  3.0  5.3  4.9  4.9  5.3  4.4  5.1  4.4       
WR study mean (dB)  —  —  —  —  —  —  4.3  —  —  —  —  —  —  —  —  —  — 
WR study SD (dB)  —  —  —  —  —  —  3.9  —  —  —  —  —  —  —  —  —  — 
Frequency (kHz) 0.125 0.25 0.5 1 2 3 4 6 8 10 11.2 12.5 14 16
DT study mean (dB)  3.5  3.7  2.9  4.3  4.5  3.8  3.5  5.6  5.6  5.6  6.5  4.8  5.7  5.3       
DT study SD (dB)  2.8  2.7  2.3  7.4  3.0  2.9  3.0  5.3  4.9  4.9  5.3  4.4  5.1  4.4       
WR study mean (dB)  —  —  —  —  —  —  4.3  —  —  —  —  —  —  —  —  —  — 
WR study SD (dB)  —  —  —  —  —  —  3.9  —  —  —  —  —  —  —  —  —  — 
FIG. 6.

The signed difference between thresholds obtained with a reference audiometer and WAHTS thresholds from the validation studies conducted at Decibel Therapeutics (left) and Walter Reed (right).

FIG. 6.

The signed difference between thresholds obtained with a reference audiometer and WAHTS thresholds from the validation studies conducted at Decibel Therapeutics (left) and Walter Reed (right).

Close modal

Two separate studies were conducted to determine the RETSPL values of the WAHTS, a boothless audiometer with new transducers. Both studies followed the ISO 389-9 standard. In both studies, however, the recruited population had median thresholds greater than 0 dB HL as measured on clinical equipment. RETSPLs were, therefore, adjusted to account for slightly increased thresholds in the study population to yield measurements that would be consistent across audiometers and transducers. Two additional validation studies with different populations that included hearing impaired individuals and different clinical reference equipment demonstrated agreement within 5 dB between the WAHTS and other audiometers, a result that is consistent with other published comparisons. Additional RETSPL studies for the WAHTS conducted with populations from diverse locations will help improve the accuracy of the final values, as has been shown with the HDA-200 and other earphones (Frank, 2001). These studies may need to constrain the inclusion criteria as has been done in prior RETSPL studies. Larger population sizes will also ensure higher statistical significance when analyzing subgroups (age, gender, and race).

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The research reported in this publication was supported, in part, by the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health under Award No. R44DC012861. The research grant funding provided financial support to Creare LLC and House Clinic. This work was also partially supported by the MEDCOM APHC and the U.S. Army Medical Research and Materiel Command under Contract No. W81XWH-18-C-0108. The views, opinions and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of the Army position, policy, or decision unless so designated by other documentation.

  1. Have you ever had trouble with your hearing (e.g., infections, ear noises, drainage, etc.)?

    Yes/No/If yes, please detail.

  2. Have you ever had an operation in your ear?

    Yes/No/If yes, please detail.

  3. Have you ever taken drugs, tablets, or been given injections that affected your hearing? Yes/No/If yes, please detail.

  4. Have you worked for several years in a place that was very noisy, i.e., where it was difficult to communicate?

    Yes/No/If yes, please detail.

  5. Did you wear any hearing protector at that time?

    Yes/No.

  6. Do you attend pop/rock concerts or discotheques? Never/Once a year/More than once a year.

  7. Do you play any musical instrument?

    Yes/No/If yes, please detail.

  8. Do you listen to personal wearable players?

    Never/Less than 2 h per week/More than 2 h per week.

  9. Have you been exposed to any loud sounds from, e.g., motorbikes, chain-saws, gunfire, fire-crackers, or explosion?

    Yes/No/If yes, what kind and how often?

  10. Does/did anyone in your immediate family have a hearing disorder?

    Yes/No/If yes, please detail.

  11. Have you ever had a hearing test before?

    Yes/No/If yes, when and where.

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