New Age Hearing Testing at your Fingertips: Shravana Mitra App

Abstract

Introduction: WHO estimated the prevalence of disabling hearing loss is 5% of the world population (430 million). People with a risk of hearing loss from noise exposure, ototoxic drugs, and comorbidities need regular hearing assessments. It is done by pure tone audiometry (PTA), requiring a skilled audiologist, special equipment, and a soundproof room. Modern technologies can help in overcoming these barriers. This study aimed to fill the lacuna by developing a new android-based application “Shravana Mitra” (Hearing companion) with features of both air conduction (AC) and bone conduction (BC) testing. Objectives: To develop, corroborate and compare smartphone application-based audiometry with PTA. Methodology: This study was done in three phases -(i) development of a mobile application, (ii) app validation in healthy individuals (iii) testing and comparison of results with PTA in individuals visiting OPD. The third phase was done as a cross-sectional observational study including 780 individuals visiting OPD of 10–60 years of age. Results: The mean age of the study population was 32.89 years with female preponderance (57%). In AC testing, 83% of the pure tone average of the mobile application was within 5 dB of PTA thresholds and 99% was within 10 dB and for BC testing, 81% was within 5 dB of PTA thresholds and 98% within 10 dB. Conclusion: Our user-friendly mobile application- Shravana Mitra is the first Indian application available in the google play store with both AC & BC testing, multiple language options and accuracy similar to PTA. Thus, it can be used as the best hearing screening tool in camps, high-risk individuals, or any healthcare setup requiring initial hearing assessment.

Introduction

The prevalence of disabling hearing loss in the world is estimated as 430 million, which is 5% of the world population according to WHO. Over 1 billion young adults are at risk of permanent, avoidable hearing loss due to unsafe listening practices [1]. A hearing assessment is most accurately done by pure tone audiometry, which needs a skilled audiologist, special equipment, and a soundproof room. In under-developed and developing countries, there is a hindrance to early diagnosis and rehabilitation for hearing care due to a lack of awareness, limited trained professionals, and expensive pro resources [2, 3].

Modern technologies have a major role in overcoming these barriers through the development of low-cost, user-friendly mobile applications for hearing screening and assessment in low-resource setups. Many self or tester-administered mobile applications are already available in the Google play store and App Store for hearing screening which is mainly based on air conduction (AC) testing. The degree and type of hearing loss can be concluded only when both air and bone conduction (BC) testing is done. But, only two applications shoebox (iOS application) and a novel app, EarBone have bone conduction testing [4, 5].

This study aims to fill the lacuna by the development of a new application (Android) with the features of both AC and BC testing, assessment of the degree and type of hearing loss, and compare its accuracy with gold standard pure tone audiometry.

Materials and Methods

Study Design

This study was done in three phases and it includes the development of a mobile application – Shravana Mitra, validation of the application by testing healthy individuals (100 healthy volunteers) and then carrying out the test in individuals with hearing loss and comparing the results with that of PTA. This cross-sectional observational study included 780 participants between the age of 10–60 years visiting the ENT department requiring pure tone audiometric assessment.

Study Population

I. For Validation by Testing Healthy Individuals

Inclusion Criteria:

• Individuals between 10 and 60 years who are visiting the ENT department.

• Individuals with no history of ear complaints such as decreased hearing, ear pain, ear discharge, ear blocking sensation, aural fullness, vertigo or tinnitus.

Exclusion Criteria:

• Individuals who are unable to cooperate (as it is a subjective study).

• Individuals with a history of ear surgery.

II. For Testing in Individuals with Hearing Loss

Inclusion Criteria:

• Individuals between 10 and 60 years who are visiting the ENT department requiring pure tone audiometry.

• Individuals with a history of decreased hearing irrespective of the duration.

Exclusion Criteria:

• Individuals who are unable to cooperate (as it is a subjective study).

• Individuals with.

  • active ear discharge.
  • foreign body in the ear canal.
  • impacted or excessive wax.
  • ear canal tenderness.
  • active episodes of giddiness.

Procedure

Phase 1: Development of an Android-Based Mobile Application

The mobile application development was done in collaboration with the Department of ECE of our Science and Technology University.

The calibration was done in the audiometry room of our hospital around 7 to 8 times to obtain an accuracy of around 5–8% concerning the already available equipment in the hospital. [In our application, a pulse was generated using the PAM (Pulse-Amplitude Modulation) technique for decibel levels.]

The calibration of the smartphone-earphone pair and TDH 39 bone conduction headphones were done using a GSI-61 audiometer with insert earphone ER-3 A and B71 Radioear bone oscillator respectively.

Phase 2: Validation of the Application

The validation of the mobile application was done by testing hundred healthy volunteers aged between 10 and 60 years, were selected as per the selection criteria mentioned above. The mean age of the volunteers was 29 years with a male-to-female ratio of 1:1. After calibration of the devices, both air conduction and bone conduction test were done using the smartphone application with appropriate headphones and validated by comparing the results to that of PTA.

Phase 3: Testing in the Attending Our Outpatient Department

The study was conducted in the outpatient department of ENT of our Hospital, Mysuru with individuals between 10 and 60 years who require pure tone audiometry assessment. Informed consent was obtained from each patient. Detailed history including name, age, sex, comorbid illnesses like Diabetes mellitus, hypertension, cardiac disorders, tuberculosis, bronchial asthma & seizures, history of ear discharge/ block/ ringing ears/ giddiness/ hearing loss, history of hard of hearing, use of any ototoxic drugs, any viral fever, any ear surgery and use of hearing aids were noted in the application.

The hearing assessment was done using a smartphone application with normal in-the-canal earphones for AC testing and bone conduction headphones for BC testing in a quiet room and results were stored in the application (Figures 1 and 2).

Fig. 1.

Hearing assessment done with the mobile application in a quiet room and a bone conduction headphone

Fig. 2.

Hearing assessment results of the mobile application

Pure tone audiometry was repeated for the same participants and statistical analysis were done by comparing the results.

Results

In our study, 780 participants were included. The mean age of the study population was 32.89 years (Table I). Male to female ratio of 1:1.3 was noted showing a female predominance of 57.3%.

Table I.

Age distribution

Age (in years) – frequency range	Number of participants
10–20 years	87
21–30 years	342
31–40 years	204
41–50 years	48
51–60 years	99
Total	780

The air conduction and bone conduction results of both ears of each patient were taken as individual readings and hence, the total was taken as 1560 (n = 780). A hearing loss of more than 50 decibels could not be assessed with this application because the limit of the highest decibel value for hearing tests is different for each mobile variant. Therefore, hearing loss levels above 50 decibels at a given frequency were excluded from the statistical analysis. For example, in air conduction testing of both the right and left ears of 780 subjects (i.e., 1560) at 250 Hz (Table II), 51 results indicated hearing loss greater than 50 decibels and were therefore excluded from the analysis

In air conduction testing including both ears, 99% of application-tested thresholds were within 10 dB difference of PTA thresholds at 250 Hz. Similarly, at 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, and 8000 Hz, it was found to be 100%, 94.6%, 99%, 96% and 88.4% respectively (Table II).

Table II.

Difference between PTA and application-based audiometry thresholds of AC test of right and left ears – all frequencies

Decibel difference	250 Hz	500 Hz	1000 Hz	2000 Hz	4000 Hz	8000 Hz
-15	0	0	0	0	0	123
-10	15	177	114	114	123	93
-5	240	402	339	321	387	609
0	738	623	641	561	714	444
5	375	262	270	258	150	126
10	126	45	66	240	96	81
15	0	0	79	0	36	18
20	15	0	0	0	0	15
25	0	0	0	15	21	18
30	0	0	0	0	0	3
Total	1509	1509	1509	1509	1527	1530

In bone conduction testing including both ears, 97% of application-tested thresholds were within 10 dB difference of PTA thresholds at 250 Hz. Similarly, at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, it was found to be 98%, 98%, 97%, and 96% respectively (Table III).

Table III.

Difference between PTA and application-based audiometry thresholds of BC test of right and left ears – all frequencies

Decibel difference	250 Hz	500 Hz	1000 Hz	2000 Hz	4000 Hz
-25	18	0	0	0	0
-20	0	27	24	0	15
-15	30	0	0	45	45
-10	180	168	129	270	126
-5	381	510	546	315	729
0	588	705	633	537	537
5	315	150	228	339	108
10	48	0	0	54	0
TOTAL	1560	1560	1560	1560	1560

In AC testing, the application-calculated threshold was more than the 10-decibel difference from the PTA threshold, particularly at 8000 Hz and 1000 Hz. At 8 kHz, 11% of values were more than the 10-decibel difference from the PTA values while at 1 kHz, it was 5.3%. In bone conduction testing, this difference is comparatively more at 4000 Hz and it was 3%.

In AC testing, 83% of the pure tone average of the mobile application was within 5dB of PTA thresholds and 99% were within 10dB (Figure 3a) and for BC testing, 81% were within 5dB of PTA thresholds and 98% were within 10 dB (Figure 3b).

Fig. 3.

3a Frequency of difference between pure tone average of PTA and mobile application in Right & Left AC.  3b Frequency of difference between pure tone average of PTA and mobile application in Right & Left BC

Discussion

A hearing assessment is the systematic use of a test or investigation to identify individuals who may be at threat for a hearing disorder or impairment and who could profit from further testing, proactive preventive strategies, and/or the appropriate level of care. If nothing is done, those with hearing loss may have greater rates of unemployment (or lower levels of employment), social alienation, loneliness, and social stigma [1, 6, 7]. Age-related hearing loss is closely linked to cognitive decline and increases the risk of cognitive issues and/or dementia [8–10]. Adults with hearing loss also had higher mortality rates, higher rates of yearly hospitalizations, and higher risks for falls [11–13].

Despite the difficulties associated with untreated hearing loss, the average individual waits 8.9 years before they take action to repair the hearing loss [14]. To more accurately identify those at threat of hearing loss, regular medical checks for elderly individuals should ask about hearing concerns [15]. By doing routine hearing exams, it is possible to better identify, diagnose, and treat hearing loss in adults [16, 17]. For those who are more likely to develop hearing loss due to circumstances like noise exposure, exposure to ototoxic chemicals, or advancing age, there are guidelines for developing screening measures [18].

The skilled audiologist will often conduct the hearing evaluation using Pure Tone Audiometry in a sound-proof chamber. A pure tone hearing test utilising Android smartphones and calibrated headphones is one of the more recent alternatives. There are already many self- or tester-administered mobile applications for hearing screening that are based mostly on air conduction testing and performed with in-the-canal headphones, in a quiet room, evaluating thresholds at various frequencies from 250 to 8000 Hz. However, only two apps—Shoebox (an iOS app) and the cutting-edge EarBone—support bone conduction testing [4, 5]. Only after performing both air and bone conduction testing can the degree and type of hearing loss be determined.

To identify hearing thresholds, Patel et al. [19] created air-conduction-based pure-tone audiometry for the smartphone application. To ensure clinical standards, the used smartphone-earphone pair was calibrated using a GSI-61 audiometer and insert earphone ER-3 A. This study was done by calibrating the earphone and application with respect to the Piano inventis audiometer and TDH 39 headphones & B71 Radioear bone oscillator.

The validity of a smartphone hearing screening technique (hearScreenTM) was assessed by Asmail et al. [20] in comparison to traditional screening audiometry, and it involved 1,070 school-age children in grades 1 to 3 (8 ± 1.1 average years) from five public schools. Supra-aural Sennheiser HD202 II headphones and Samsung Galaxy Pocket Plus S5301 smartphones running the hearScreenTM Android OS were utilised (Sennheiser, Wedemark, Germany). In this study, Sennheiser CX120 BT wireless earphones (for AC testing) and BS01 bone conduction headphones were used in conjunction with the Android-based “Shravana Mitra” app on a Samsung Galaxy A71 phone (for BC testing).

In 63 adults, Sandstrom et al. [21] performed a comparative investigation in community clinics to determine the precision and dependability of mobile-based self-test audiometry. When compared to reference audiometry, air conduction hearing thresholds for octave frequencies 0.5 to 8 kHz showed a 90.6% sensitivity and 94.2% specificity for identifying hearing loss more than 40 dB. According to the current study, 99% of the mobile application’s pure tone average was under 10 dB and 81% was within 5 dB of PTA thresholds during air conduction testing.

In a group of forty volunteers, Nicholas A. Dewyer et al. [5] created and validated the EarBone bone conduction threshold test application. They discovered that 61% of the app’s thresholds were within 5 dB of pure tone audiometry thresholds and 79% of the app’s results were within 10 dB. In the results of the current study, in bone conduction testing, 80% of the pure tone average of the mobile application was within 5 dB and 98% was within 10 dB of PTA thresholds.

In this study, it was found that in air conduction testing, the application calculated threshold is more than the 10-decibel difference from the PTA threshold, particularly at 8000 Hz and 1000 Hz. At 8 kHz, 11% (n = 59) of values are more than the 10-decibel difference from the PTA values while at 1 kHz, it was 5.3% (n = 27). In bone conduction testing, this difference is comparatively more at 4000 Hz and it was 3% (n = 20).

Android library provides a way to control the volume of the device in the form of a float value ranging from 0 to 100.0. When we are increasing or decreasing the decibel value, we are just increasing the volume value. When the conversion of decibel value into a range of 0 to 100 crosses the 100 max, the increase in the decibel will be limited to produce accurate results. The maximum possible decibel value of a mobile depends on the reference value that we have set and also the maximum volume that the phone can produce. This is one of the limitations that the Android audiometry test has when compared to pure tone audiometry [22]. While testing our application, it was found that more than 50 decibels of hearing loss could not be assessed by this application as the limitation of the highest decibel for hearing tests differs for each mobile variant.

Shravana Mitra application has multiple language options which makes it a user-friendly application and also the cloud-based server data storage facility helps in further monitoring and management. There are few opportunities for early hearing loss screening in developing nations, where more than 80% of people with hearing loss live [23, 24] as a result of obstacles such as the high cost of screening audiometers, the need for operator training to perform conventional manual audiometric screening, the excessive number of referrals brought on by the absence of environmental noise monitoring, and inadequate data collection [25]. A reliable and efficient screening tool for hearing loss is the use of a smartphone application-based audiometry.

Our mobile application assesses hearing loss only up to 50 decibels and it varies based on the mobile model. Hence, that is a limitation of hearing assessment in case of high decibel loss. Further research should be carried out to add additional features for contralateral ear masking.

Conclusion

According to WHO estimates, 430 million people, or 5% of the world’s population, suffer from hearing loss that is incapacitating. If the hearing evaluation can be completed at our convenience, such as in our home environment, it will eliminate the need to travel to a hospital or speech and hearing centre. Early detection of the hearing impairment allows for proper therapy. In light of this, we developed an Android-based mobile application for hearing assessment.

As most of the available apps for hearing testing provide only access for air conduction testing, both air conduction and bone conduction threshold assessments will be done by our Android mobile application- Shravana Mitra and the results were almost similar to that of PTA thresholds. This app helps you to find out your hearing ability in a user-friendly way and also provides results to the extent to conclude the severity from mild to moderate and the type of hearing loss. Thus, this application can be used as the best screening tool for regular hearing assessment in individuals with a risk of hearing loss due to noise exposure, any comorbidities or ototoxic drugs and also helps anyone to check their hearing at any time. This can also be used in hearing screening during camps, and in any low-resource setups. The application is also available in different languages, making it user-friendly.

It is available for free of cost in the google play store-.

https://play.google.com/store/apps/details?id=com.hearingaid.jsstu.HearingAid.

Data Availability

Data transparency has been maintained.

Declarations

Ethics approval and consent to participate

All procedures performed in the study were in accordance with the institution’s ethical standards.

Informed Consent

Informed consent was obtained from all individual participants included in this study.

Competing interests

All the authors declare they have no conflicts of interest and have not received any funding.