| ORIGINAL ARTICLE |
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| Year : 2019 | Volume
: 25
| Issue : 2 | Page : 53-58 |
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Acoustic radiation: Relation with frequency and its impact on threshold estimation
Preeti Sahu1, Debadatta Mahallik2
1 Department of ENT & HNS, Audiologist, ICMR NTF HI Project, AIIMS, Raipur, Chhattisgarh, India
2 Department of ENT, Audiology Unit, Pt. JNM Medical College, Raipur, Chhattisgarh, India
Correspondence Address:
Mrs. Preeti Sahu
BERA Room, 1214-A, First Floor, Medical College Building, Gate No. 5, GE Road, Tatiband, Raipur - 492 099, Chhattisgarh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/indianjotol.INDIANJOTOL_38_18
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Background: The most important diagnostic feature of the audiogram is the air-bone gap. Both false and missed air-bone gap lead to misdiagnosed. Acoustic radiation from the bone vibrator, especially at high frequency, causes hearing through the air-conduction reflects false air-bone gap. Materials and Methods: A total of 67 (134 ears) individuals with age ranged between 14 and 48 years (mean age: 36.1 years) were taken in this study. Who had external auditory canal clean and dry with intact tympanic membrane and the air-bone gap >10 dB in high frequencies (i.e., 2000 Hz, 3000 Hz, and 4000 Hz) were included in the study. All the clients who had air-bone gap >10 dB in the frequencies of 2000, 3000, and 4000 Hz were reassessed for their bone-conduction thresholds by closing the external ear canal with the patient's own index finger during testing. Study Design and Statistics: This was an experimental study where statistical analysis and ANOVA was done to compare between open ear canal and closed ear canal condition among frequencies. One-way repeated measure ANOVA along with Bonferroni comparison test was done separately for open ear canal and closed ear canal conditions. Results: Results revealed significant difference in air-bone gap (ABG) between two conditions which were increasingly more for higher frequencies, that is, 2000 Hz, 3000 Hz, and 4000 Hz compared to lower frequencies. Conclusion: Acoustic radiation is the sound energy that may be detected by air-conduction mechanisms which escape from a bone vibrator. When the external auditory meatus is occluded, the acoustic radiation phenomenon can be controlled or avoided, enabling bone measures at the higher frequencies, especially at 2000, 3000, and 4,000 Hz to be more accurate. Thus provides more accurate audiometric diagnosis which is most importantly based on ABG.
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