|Year : 2015 | Volume
| Issue : 2 | Page : 111-113
Effects of background noise on transiently evoked otoacoustic emissions in newborn hearing screening
Chandrakant Vishwakarma1, Rupali Mathur1, Vikas Sinha2, Rajesh Vishwakarma3
1 Shabda Brahma Speech and Hearing Clinic, Ahmedabad, Gujarat, India
2 Department of ENT, M. P. Shah Government Medical College, Jamnagar, Gujarat, India
3 Department of ENT, Civil Hospital, B. J. Medical College, Ahmedabad, Gujara, India
|Date of Web Publication||20-Apr-2015|
Shabda Brahma Speech and Hearing Clinic, 3rd Floor, Aakar Complex Sardar Patel Stadium Road, Navrangpura, Ahmedabad - 380 014, Gujarat
Source of Support: None, Conflict of Interest: None
Introduction: Newborn hearing screening program is one of the services offered in Neonatal Intensive Care Units (NICU) by most of the neonatologist today. Aim of the Study: Present study aimed to investigate the ambient noise levels which allow successful transient evoked otoacoustic emission testing. Method: 25 normal hearing neonates (group 1) and 25 normal hearing adults (group 2) participated in the study. Both groups were tested at 30 dB sound pressure level (SPL), 40 dB SPL and 50 dB SPL noise levels. Results and Discussion: Tests results showed with increase in noise levels number of passing subjects decreased and also testing was done at times more than once. Conclusion: Tester should take care of noise levels while doing the test in NICU, which can give false negative responses.
Keywords: Transient evoked otoacoustic emission, newborn hearing screening program, noise level
|How to cite this article:|
Vishwakarma C, Mathur R, Sinha V, Vishwakarma R. Effects of background noise on transiently evoked otoacoustic emissions in newborn hearing screening. Indian J Otol 2015;21:111-3
|How to cite this URL:|
Vishwakarma C, Mathur R, Sinha V, Vishwakarma R. Effects of background noise on transiently evoked otoacoustic emissions in newborn hearing screening. Indian J Otol [serial online] 2015 [cited 2019 Jul 19];21:111-3. Available from: http://www.indianjotol.org/text.asp?2015/21/2/111/155296
| Introduction|| |
Hearing is one of the precious senses gifted to human beings and it's like nightmare to describe life without hearing. Hearing loss is the invisible disability which often goes unnoticed until tested or keenly observed in newborns. As per national plan for control and prevention of hearing impairment and deafness (2003), 76.07 million people are afflicted with hearing impairment in India.  Hearing loss in infants have detrimental effects on language development if not identified and rehabilitated at early age. Rhode Island Hearing Assessment Project gave the first published statement on universal screening for every infant.  According to Joint Committee on Infant Hearing Screening, 2013 universal newborn hearing screening should be done before discharge or within 1-month of birth, and proper diagnosis by 3 months of age.  Also, infants with confirmed loss should be provided with appropriate amplification device by 6 months of age.
Sophistication in technology has made ways to screen babies having hearing loss at early age. Various tests like otoacoustic emission (OAE), auditory brainstem response or auditory steady-state response (ASSR) can give us hearing status. However, administration time and interpretation of results vary in all the tests. OAE test is favored in Hearing Screening program due to its procedural requirement, administration time and result in interpretation. Also it has good sensitivity with lesser cost to the client. OAEs are sound generated within cochlea, either spontaneously or evoked in response to acoustic stimulation. 
Any test can be a strong tool if it has good sensitivity and specificity. Lesser ambient noise is one of the prerequisite for better transient evoked OAE (TEOAE) testing, else the result may be influenced. Numerous studies conducted on the line of sensitivity and specificity of TEOAEs have expressed their views. Pröschel and Eysholdt reported sensitivity of 93% and specificity of 67% in their study.  Kaul found sensitivity and specificity of TEOAE and DPOAE in hearing screening about 90%.  In 2005, Abdullah et al. conducted a study and said that portable TEOAE instrument is very sensitive but moderately specific screening tool.
As per Popelka et al., there are three different types of noises which an effect the responses in DPOAE: Equipment noise, environmental noise and subject related noise.  Usually, nowadays all the latest OAE equipment have very less or no equipment noise, and the environmental noise can be controlled by the clinician while testing in a particular environment by some modifications. It is difficult at times to control the subject related noise especially if its noisy breathing or subject is not stable while testing. White et al., report breathing noise as major noise in newborns. 
In day to day practice, we often encounter ambient noise as the prime factor affecting OAE recordings adversely. However, there are limited reports available on this. As per the Whitehead et al., background noise results in false DPOAE responses.  Rhoades et al., investigated the effect of background noise on click-evoked OAEs and found that ambient noise levels should not exceed 50-55 dB A of noise for accurate recordings of OAE.  We could not find any published study which would have taken lower level of noise into accountability for PASS/REFER criteria. Present study tries to investigate the different levels of noise, which can affect the OAE measurement.
| Methods|| |
Present study had subjects in two groups: Group 1 of 25 adults (50 ears) and Group 2 of 25 neonates (50 ears). Adults were in the age range of 18-30 years and neonates from 10 days to 27 days. Both males and females randomly participated in the study. They full filled following criteria:
- All subjects had otoscopy done and no history of ear discharge
- Every subject underwent tympanometry to check for normal middle ear functioning
- Hearing test was done in all the subjects to ascertain normal hearing status. Adults underwent pure tone audiometry, and neonates underwent ASSR testing at 35 dB sound pressure level (SPL) in sound-treated conditions.
Otoscopy was done by Certified Medical Practioner at the Tertiary Centre, Ahmedabad. Pure tone audiometry was carried out using MA-42 double channel clinical audiometer, tympanometry was done using interacoustic AT235 h instrument, OAE and ASSR testing done on intelligent hearing system, at the Advanced Audiological Centre, Ahmedabad. Noise was presented using free field system from MA-42 double channel audiometer at various levels.
In TEOAE testing, broadband click at 80 dB SPL, in nonlinear mode used with the appropriate probe as per the subject. Pure tone audiometry was done in octave interval from 250 to 8000 Hz in air conduction and 250-4000 Hz for bone conduction. During impedance and OAE testing, adults were instructed to be relaxed and calm while neonates were tested when they were either sleeping or quiet. ASSR testing was carried for neonates to confirm normal hearing, 40 dB SPL stimuli across frequencies 250-4000 Hz. During the study, noise was presented through calibrated MA-42 double channel audiometer's free field system, positioned at 45° azimuth from both sides at distance of 1.5 m from the subject.
Following steps done in the study:
- Transient evoked otoacoustic emission in quiet
- Transient evoked otoacoustic emission in 30 dB SPL, 40 dB SPL and 50 dB SPL through both speakers simultaneously.
Recordings noted in terms of amplitude and signal-to-noise ratio (SNR) from all the four conditions and compared.
| Results and Discussion|| |
Results of the present study were evaluated in following ways:
- Number of subjects (adults and neonates) passing the test overall in quiet
- Number of subjects (adults and neonates) passing the test in quiet across frequencies
- Number of subjects (adults and neonates) passing the test overall in various noisy conditions
- Number of subjects (adults and neonates) passing the test across the frequencies.
In the test passing criteria for TEOAE was kept at 3 dB SNR, accordingly the results were tabulated as follows:
From [Table 1] below-mentioned points are clear:
|Table 1: Results of the subjects passing the test in various conditions across frequencies|
Click here to view
- Noise has adverse role in TEOAE recording, with an increase in noise levels the number of subjects passing the test decreased globally and across frequencies
- Maximum number of neonates passing the test were at 3000 Hz across different conditions, by which it is possible to say that the response at 3000 Hz is more robust compared to adults. Also, maximum number of adults met the passing criteria at 1500 Hz. This finding is similar to the results from the study done by Shi et al. in 2010 
- Less number of subjects passing test result at 4000 Hz could be due to lesser amplitude at the frequency
- Globally, more number of neonates passed the test when compared to adults across the testing conditions is concurrent with fact that neonates have robust OAE amplitudes compared to adults as per Brown et al., 1994 
- There is not much difference between adults and neonates passing the test across frequencies at 40 dB SPL noise and 50 dB SPL noise, suggesting at higher levels of background noise OAE recording is affected
- There were some subjects passing the test at higher noise levels of 50 dB SPL also which is in line with Rhoades et al. study, where they reported successful recording of TEOAE even at 55 dB SPL of background noise. However, in the present study, we would say clinician has to keep close monitoring while doing the test for the result. There could be false positive or false negative.
| Conclusion|| |
Present study strongly supports the fact of doing TEOAE screening in quieter conditions to avoid wrong interpretations. Clinician should discuss the test conditions with the management or the doctor regarding the test process and appropriate room for carrying the test. Parents should also be counseled regarding the test process so as to make neonates comfortable to avoid any movement of the baby during the test.
| References|| |
Nikam S. Hearing Impairment. In: Kundu CL, Editors. Status of Disability in India - 2003. New Delhi: Rehabilitation Council of India; 2003.
White KR, Vohr BR, Behrens TR. Universal new-born hearing screening using transient evoked otoacoustic emissions: Results of the Rhode Island Hearing Assessment Project. Semin Hear 1993;14:18-29.
American Academy of Pediatrics, Joint Committee on Infant Hearing. Supplement to the JCIH 2007 position statement: Principles and guidelines for early intervention after confirmation that a child is deaf or hard of hearing. Pediatrics. 2013;131. http://pediatrics.aapublications.org/content/131/4/e1324.full.html
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Kemp DT. Otoacoustic emissions in perspective. In: Robinette MS, Glattke TJ, editors. Otoacoustic Emissions: Clinical Applications. New York: Thieme; 1997. p. 1-21.
Pröschel U, Eysholdt U. Specificity and sensitivity of transient click-evoked otoacoustic emissions (TEOAE). Laryngorhinootologie 1995;74:481-8.
Koul A. Effectiveness of DPOAE and TEOAE in hearing screening. Unpublished Independent Project, University of Mysore, Mysore; 2003.
Popelka GR, Karzon RK, Clary RA. Identification of noise sources that influence distortion product otoacoustic emission measurements in human neonates. Ear Hear 1998;19:319-28.
Whitehead ML, Lonsbury-Martin BL, Martin GK. The influence of noise on the measured amplitudes of distortion-product otoacoustic emissions. J Speech Hear Res 1993;36:1097-102.
Rhoades K, McPherson B, Smyth V, Kei J, Baglioni A. Effects of background noise on click-evoked otoacoustic emissions. Ear Hear 1998;19:450-62.
Shi BY, Liu JF, Wang NY, Yuan JJ, Fu X, Li L, et al.
Comparison of transient evoked otoacoustic emissions in newborns and adults with frequency specific approach. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi 2010;45:206-11.
Brown AM, Sheppard SL, Russell PT. Acoustic distortion products (ADP) from the ears of term infants and young adults using low stimulus levels. Br J Audiol 1994;28:273-80.
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