Setting and Hearing Assessment:
We invited students to the Ear, Nose and Throat (ENT) OPD, Jinnah Postgraduate Medical Centre, Karachi (JPMC) for tuning fork tests (TFTs) and PTA. We explained whole procedure to the students and acquired informed consent on individual basis. Using a structured proforma, we collected sociodemographic information, electroacoustic device usage history and relevant medical and surgical history from each participant. Sociodemographic data included age, gender, year of study and residence. We also asked about type of electroacoustic device (insert type earphones, supraural headphones or Bluetooth handsfree), per day duration, source to which these devices were connected and using since when.
Postgraduate trainees of ENT performed Rinne test and Weber test on each participant with a 512 Hz tuning fork. We regarded centralized hearing of the tuning fork as normal while base of tuning fork placed at forehead or upper incisors. For Rinne test we applied loudness comparison technique. In which we kept the base of tuning fork on mastoid process to assess bone conduction (BC). For air conduction (AC) we located prongs of tuning fork lateral to the external auditory canal (EAC). We considered positive (normal) result when air conduction proved better than bone conduction (AC >BC).
Immediate next to TFTs we sent our students for PTA. We instructed them regarding the test procedure. Trained audiometrists performed PTA in a soundproof booth. They assessed each participant first for air conduction (AC) at octave frequencies i.e. 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 8000 Hz. To differentiate the type of hearing loss from conductive to sensorineural, they also investigated bone conduction when AC thresholds were beyond normal range. Significant air-bone gap was considered greater than 15 dB (decibel) between air and bone conduction thresholds. Test frequencies for bone conduction were from 500 Hz to 4000 Hz. They generated the findings of PTA on an audiogram. To classify hearing loss at each frequency we applied WHO grading of hearing impairment. Where normal was 25 dB or less, mild hearing loss from 26-40 dB, moderate from 41-60 dB, severe from 61-80 dB while profound hearing loss including deafness was 81dB or greater.