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.