Abstract Background and Objectives: There is an exponential increase in the usage of mobile phones throughout the world. Mobile phone handsets are usually held near the ear during conversations and these phones emit radiations (electromagnetic fields). These radiations have a propensity to cause biological health hazards. This has raised the question of whether the usage of mobile phones has any detrimental effects on the hearing of the user. The aim of this study was to evaluate the auditory acuity in normal subjects using mobile phones and subjects not using. Methods: A total 400 subjects were selected considering inclusion and exclusion criteria. Among these 300 were mobile users and 100 non-users. These two groups were subjected to pure tone audiometric assessment. The resulting data was statistically analyzed. Results: There was an increase in the hearing thresholds with p-value <0.05 at frequencies of lkhz (BC), 4khz (AC and BC), 6khz(AC) and 8khz(AC) in the mobile phone users compared to that in non-users. The thresholds in the dominant ear were increased with p-value <0.05 at frequencies lkhz(AC and BC), 2khz(AC and BC), 4khz(AC and BC), 6khz(AC) that compared in non-dominant ear. The different duration of exposures (in months) and the average time (min/day) exposures did not have any significant effect on the hearing thresholds. Conclusion: There is a mild increase in the hearing thresholds in mobile users, but the probable cause of hearing impairment cannot be proved by this study and the possible pathophysiology is also not understood and it needs to be investigated further... Key words: Mobile phones, electromagnetic fields (EMF), Pure tone audiometry, Air conduction (AC), Bone conduction (BC).

1. R G U H S J o u r n a l of Me d i c a l Sciences
O R I G I N A L A R T I C L E
Effects of Mobile Phones on Auditory acuity
BalajiPA*, KailashN**
*Assistant Professor of Physiology
**Professor and Head" Department of ENT
Dr. B RAmbedkar Medical College,
Bangalore, India.
Address for correspondence:
Dr. Balaji PA,Assistant Professor,
Dept, ofPhysiology,
Dr. B RAmbedkar Medical College,
Kadugondana Halli, Bangalore- 45.
drpaba@rediffmail.com
Dr.Kailash N, Professor & HOD,
Department ofENT,
Dr. B RAmbedkar Medical College,
Kadugondana Halli, Bangalore- 45.
kaigaipraj@yahoo.com
Abstract
Background and Objectives: There is an exponential
increase in the usage of mobile phones throughout the
world. Mobile phone handsets are usually held near
the ear during conversations and these phones emit
radiations (electromagnetic fields). These radiations
have a propensity to cause biological health hazards.
This has raised the question of whether the usage of
mobile phones has any detrimental effects on the
hearing of the user. The aim of this study was to
evaluate the auditory acuity in normal subjects using
mobile phones and subjects not using.
Methods: A total 400 subjects were selected
considering inclusion and exclusion criteria. Among
these 300 were mobile users and 100 non-users. These
two groups were subjected to pure tone audiometric
assessment. The resulting data was statistically
analyzed.
Results: There was an increase in the hearing
thresholds with p-value <0.05 at frequencies of lkhz
(BC), 4khz (AC and BC), 6khz(AC) and 8khz(AC) in
the mobile phone users compared to that in non-users.
The thresholds in the dominant ear were increased
with p-value <0.05 at frequencies lkhz(AC and BC),
2khz(AC and BC), 4khz(AC and BC), 6khz(AC) that
compared in non-dominant ear. The different duration
of exposures (in months) and the average time
(min/day) exposures did not have any significant
effect on the hearing thresholds.
Conclusion: There is a mild increase in the hearing
thresholds in mobile users, but the probable cause of
hearing impairment cannot be proved by this study
and the possible pathophysiology is also not
understood and it needs to be investigated further...
Key words: Mobile phones, electromagnetic fields
(EMF), Pure tone audiometry, Air conduction (AC),
Bone conduction (BC).
Introduction
The ability to hear and communicate with each other is
a precious gift given by the creator of the universe to
the mankind. Hearing is possible due to the presence of
a highly specialized and delicate structure that is the
ear. Human ear is exposed to microwaves of different
frequencies, emitted by different sources such as
human speech, music (from radio, television), noise
(from road traffic, air traffic) and from many electronic
equipments such as the mobile telephones.
The use of mobile phones is rapidly increasing world
wide. Mobile phones transmit and receive microwave
radiation at frequencies of about 422 Hz, 850 Hz,
900Hz, 1800Hz, and 1900Hz. The radiation given off
by mobile phones is estimated in terms of SAR-
Specific Absorption Rate and Power density. It is
measured using cellular radiation detectors. Most of
mobile phones used by people, operate in frequency
bands of 900MHz and 1800MHz and they meet the
International commission on non-ionizing radiation
protection (ICNIRP) Guidelines'. ICNIRP exposure
limits for 900MHz frequency is: SAR- 2W/Kg, Power
density- 4.5W/m2
.
The mobile manufacturers get certification from
ICNIRP for their different models and the radiation
25

2. given off by the mobile phones are set within the
exposure limits. However, some research works have
found that these radiations can cause increase in
hearing thresholds, biological changes such as damage
to DNA, thermal and non thermal changes, breakdown
in immune system and rotation of water/fluids and
some organic molecules. Close range exposure to
these electro magnetic fields allows 75% ofthe energy
generated by the mobile system to penetrate the head,
reaching a depth of several centimeters2' and
potentially affecting structures like the hypothalamus,
ocular globe, the optic nerve, the meninges and the
inner ear. The use of mobile phones can cause
symptoms like fatigability, changes in behavior,
nausea, headache, anorexia, and sleep disorders. Their
usage is also related to occurrence of lymphomas and
tumors of central nervous system. The harmful effects
of the radiofrequencies are related to their capacity to
induce electric currents and raise the internal
temperature ofvarious physiological systems.
Mobile phone use necessitates holding it in close
proximity to the ear. The wide spread use of mobile
phone has given rise to the question of whether the
electromagnetic fields emitted by mobile phones is
detrimental to the hearing of their users. A study
conducted in Valencia, Spain revealed that frequent
use of mobile phone over a medium term period can be
correlated with mild hearing loss not observed in non
mobile users4.The hypothesis being tested is that, there
is impairment of auditory acuity (threshold) in mobile
phone users. Till date there is only a limited knowledge
about interaction between mobile phones and auditory
acuity.
Therefore an attempt is made to study the effects of
mobile phones on auditory acuity, using pure tone
audiometer.
Materials and Methods
Materials
Source o fdata: The study was conducted in a sample
consisting of 400 normal subjects, who were selected
from a total of486 subjects ofdifferent age groups (18-
50 years) and of either gender, residing in Bangalore
city. They were divided into test group and the control
group. 86 subjects were excluded from the study and
this was based on the inclusion and exclusion criteria.
RG U H S Jo u r na l of Me d i c a l Sciences
Test Group: It comprised of300 normal subjects, who
were using mobile phone regularly. The duration of
mobile phone usage by each subject was noted. The
most frequent side of ear used by the subject to hear
using a handset during conversations was tenned as
the dominant ear and the other the non-dominant ear.
All the subjects were selected by considering the
inclusion and exclusion criteria.
Control Group: It comprised of 100 normal subjects
not using mobile phone. All the subjects were selected
by considering the inclusion and exclusion criteria.
Inclusion criteria
1 Mobile phone users (test group)
2 Non mobile phone users (control group)
3 Age group 18-50 years.
Exclusion criteria
1. Hypertensive patients.
2. Diabetic patients
3. History ofconsumption ofototoxic drugs in
past 3 months.
4. History ofear surgeries performed in the past.
5. History ofrecent infection in ear, nose and throat.
6. Noise induced hearing loss (as evaluated by
history of residence, occupation and pure tone
audiometry).
7. Smokers and tobacco users.
Protocol
1. All subjects were given a prepared questionnaire
to answer. This questionnaire revealed:
a. Socio- Demographic data.
b. The patient's assessment ofhearing ability.
c. Whether satisfies inclusion criteria.
d. Rules out exclusion criteria.
2. Written consent was obtained from the subjects
after explaining the procedure.
3. A general physical and systemic examination was
conducted in all subjects.
4. A detailed ear, nose and throat examination was
carried out to rule out sub-clinical infection or
other pathology.
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3. R G U H S J o u r n a l of Me di c al Sciences
5. Random blood sugar test was done using a
Glucometer (to exclude undetected diabetes).
6. Taking into consideration the predetermined
inclusion and exclusion criteria, study subjects
were selected and designated into case and
control groups.
7. An assessment of auditory acuity using a pure
tone audiometer [ARPHI500 MK 1]was done.
Auditory acuity is the lowest level of sound threshold
in decibels, at a particular frequency, at which the
human ear can perceive it as a sound. The parameter of
auditory acuity studied was the hearing threshold for
air conduction and bone conduction at different
frequencies. Pure tone audiometer contains sound
thresholds in decibels and sound frequencies in Hertz.
Using this audiometer, audiograms were recorded
separately for both ears of the selected subjects in a
sound proof room. The audiogram chart thus obtained
depicted the auditory acuity ofthe particular ear.
The duration of mobile phone usage by each subject of
the test group was considered. The duration of mobile
usage by a subject was taken in terms of number of
months of usage and the average usage time per day
was calculated by dividing the total call duration (in
minutes) by the total number of days of usage of
mobile phone. The total call duration was obtained
from the call register menu of the particular mobile
phone. The recordings were entered in their respective
proforma, based on which master chart was developed.
Similarly, hearing thresholds for air conduction and
bone conduction at different frequencies (as in the pure
tone audiometer) of the control group was also
recorded and entered in a separate master chart.
Statistical treatment ofthe data
The data collected was entered in master charts and
statistical package for social sciences (SPSS) was used
for analysis of data using statistical methods like
mean, standard deviation, T-test andANOVA.
Level ofsignificance reckoned as:
0.05<P<0.10 —Suggestive significance;
0.01<P 0.05 —Moderately significant;
p<0.01 —Strongly significant.
Any model of mobile phone marketed for public use,
has to comply with ICNIRP guidelines for permissible
standard of specific absorption rate and power density.
Thus it is implicit that these radiation parameters do
not vary widely among the models of mobile phones
available in the market. Mobile phones are being
operated at different frequency bands and in India
most ofthe GSM operators use the 900MHz band. Any
mobile phone being operated at any frequency again
will have to comply with the permissible standard of
specific absorption rate and power density. Hence, in
this study these radiation parameters were not
measured and compared with impairment of auditory
acuity. Nokia, Motorola, Reliance, Sony Ericsson
were the common models of mobile phones used by
the subjects in test group. No comparison between
these models ofmobile phones was done as all models
ofmobile phones have obtained certification as per the
ICNIRPGuidelines.
Pure tone audiometry
Instrument
ARPHI [500 MK I] audiometer is a simple, easy to use
instrument and works on both 230 volts AC supply and
15 volts DC supply with a built-in voltage regulator
circuit. The model has facilities for air and bone
conduction with noise masking and tone decay tests.
Ear phones are used to test hearing by air conduction
and a small vibrator placed over the mastoid is used to
test hearing by bone conduction. All audiometers
incorporate a calibration circuit which allows the
output sound level to be set at each frequency. The
signals presented to the subject by an audiometer are
characterized by its frequency, sound pressure level
and wave form which are all controlled.
Method: The method is based on American Society
for Speech and Hearing Association [ASHA] 1978
guidelines for manual pure tone audiometry (PTA)5.
Interpretation of an audiogram:
Conductive deafness - Conductive deafness is
indicated by raised air conduction thresholds (25 dB)
and a normal bone conduction threshold with a wide
air- bone gap of 15 dB or more.
Sensorineural deafness -Sensorineural deafness is
indicated by raised air and bone conduction thresholds
(Both >25 dB) and the air bone gap does not exceed 10
dB.
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4. R G U H S J o u r n a l of Me d i c a l Sciences
Mixed deafness- Mixed deafness refers to raised air
and bone conduction thresholds with an air bone gap
ofgreater than 15dB.
Degree ofhearing loss [WHO Classification 1980]
Normal 0-25dB
Mild 26-40dB
Moderate 41-55dB
Moderately severe 56-70dB
Severe 71-91dB
Profound >91 dB
All subjects in both the groups were subjected to pure
tone audiometry as per the above protocol and
guidelines. In each case air and bone conduction
thresholds were recorded. The data was entered into
separate master charts for ease ofstatistical analysis by
the methods already mentioned. The results thus
obtained and observations made are presented in the
following section.
Results and analysis
After statistical treatment of the data collected, the
following were the results obtained and observations
made: There was an increase in the hearing thresholds
with p-value <0.05 at frequencies of 1khz, (BC), 4khz
(AC and BC), 6khz(AC) and 8khz(AC) in the mobile
phone users compared to that in non-users. The
thresholds in the dominant ear were increased with p-
value<0.05 at frequencies khz(AC and BC), 2khz(AC
and BC), 4khz(AC and BC), 6khz(AC) that compared
in non-dominant ear. The different duration of
exposures (in months) and the average time (min/day)
exposures did not have any significant effect on the
hearing thresholds.
Table I- Comparison of auditory acuity in test group and control group
Frequency AC/BC
Test group(right
&left ears) (n=600)
Control group(right
&left ears) (n=200) t-value
p-value
Mean SD Mean SD
0.25khz
AC 13.84 2.64 13.95 2.49 0.38 >0.702
BC 16.96 2.79 17.55 2.61 1.98 <0.048
0.5khz
AC 12.45 2.77 12.50 2.80 0.17 >0.868
BC 14.23 2.22 14.70 1.71 2.01 <0.045
lkhz
AC 11.36 2.46 10.35 1.28 4.01 <0.0001
BC 14.65 2.09 13.93 1.28 3.32 <0.001
2khz
AC 11.46 2.58 10.55 1.73 3.39 <0.001
BC 14.10 2.51 13.55 1.93 2.09 <0.037
4khz
AC 7.15 2.42 6.69 2.49 1.75 >0.081
BC 11.65 2.76 10.75 2.85 3.01 <0.003
6khz AC 5.04 2.19 4.80 2.75 0.98 >0.326
8khz AC 3.43 2.59 3.90 2.42 1.68 >0.093
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5. RG U H S j o u r n a l of Me di c al Sciences
Table II - Comparison of thresholds between the Dominant and Non-dominant ear
within test group
Frequency AC/BC
Dominant ear Non-dominant ear
t-value
p-value
(2 tailed)
Mean SD Mean SD
0.25khz
AC 13.83 2.64 13.85 2.63 0.38 >0.71
BC 16.95 2.79 16.97 2.79 1.0 >0.32
0.5khz
AC 12.40 2.75 12.50 2.78 1.91 >0.06
BC 14.22 2.23 14.25 2.20 1.42 >0.16
lkhz
AC 11.45 2.39 11.27 2.51 2.21 <0.028
BC 13.98 2.05 13.88 2.12 2.13 <0.034
2khz
AC 11.57 2.50 11.35 2.65 2.87 <0.004
BC 13.55 2.51 13.55 2.51 0 1.00
4khz
AC 6.87 2.45 6.52 2.37 4.15 <0.001
BC 10.83 2.70 10.67 2.81 2.92 <0.004
6khz
AC 5.20 2.34 4.88 2.02 3.74 <0.001
BC - - - - - -
8khz
AC 3.75 2.622 3.12 2.52 5.52 <0.001
BC - - - - - -
Discussion
In this present study 300 mobile phone users and 100
non-mobile phone users were selected considering the
inclusion and exclusion criteria and were subjected to
Pure tone audiometric testing. The data was analyzed
using appropriate statistical methods.
The table I shows the comparison of hearing
thresholds between the control group and the test
group. It is evident that in the Test group, the mean
hearing thresholds at frequencies Ikhz, 2khz, 4khz,
6khz are increased compared to that in the control
group with a significant p valued).05.
Shayani et al concluded in their study by saying that,
although pure-tone audiometric studies are less
sensitive in measuring cochlear functions, the results
of the present study, show that pure-tone threshold in
users is different from nonusers; however, thresholds
were in normal limits, perhaps the longer use could be
associated with the greater lesions.8
Pure tone audiometric thresholds in dominant and the
non-dominant ear (Test group): The table II shows the
mean thresholds in the dominant and the non­
dominant ears. It is evident that the mean thresholds in
the dominant ear is increased, with a significant p-
value of <0.05 at frequencies of 1 kHz (AC and BC),
2kHz (AC and BC), 4 kHz (AC and BC), 6 kHz (AC)
and 8kHz (AC).
This finding is in concordance with study conducted
by Kerekhanjanarong to detect the effect of mobile
phones on audiologic system, which also found that
the hearing threshold of the dominant ear was worse
than the non-dominant ear 6. There is a possibility of
the electromagnetic radiations affecting the myelin
sheaths of cells and eventually leading to an
impairment of hearing capability7
. These hazards are
probably due to the thermal and non-thermal effects of
the electromagnetic fields ofmobile phones.
Based on the currently available research information
and the observations made in this study, it is difficult to
substantiate whether the radiations have any
predilection to affect air conduction or the bone
conduction or both. Moreover, the mobile phones
always emit the maximum power for a few seconds
during initiation of the connection with the other
mobile phone. The telephone rings only after it has
received this powerful transmission and the power
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6. R G U H S J o u r n a l of Me d i c a l Sciences
decreases to the level which is just enough for the
connection. This protective feature of the mobile
phones may have a role in lesser affection of the
auditory system
Conclusions
1. Subjects using mobile phones have significantly
higher thresholds in their dominant ears than the
non-dominant ears, but within accepted normal
limits.
2 Significant differences in thresholds of the two
ears of test subjects are seen particularly in the
middle and higher frequencies.
3 Mobile users in general have higher hearing
thresholds than their non-mobile using
counterparts.
4 Correlation between duration of mobile phone
usage and average daily exposure, with
worsening of auditory acuity could not be
demonstrated by the current study.
Guidelines for mobile phone users
1. Use of hands free devices and other protective
devices, such as Blue Tooth and Ear phones.
2. Shorter Conversation periods and use for
Essential purposes only,
3. Use of telephone with low electromagnetic fields
emissions (SAR- 2W/Kg, Power density-
4.5W/m2)
4. Regular audiological screening (preferably once
in 6 months).
Acknowledgement:
Thanks to Dr. Gangaboraiah, Statistician.
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varying electric, magnetic and electromagnetic
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2. Stuchly M. A. Biological concern in wireless
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3. Weinberg Z, Richter ED. Cellular telephones and
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A doctor is a man who writes prescriptions till the patient
either dies or is cured by nature
John Taylor
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