Abstract (summary)
TranslateAbstractThis study looked at outputlevelsproduced by
new generationpersonalmusic systems (PMS), at thelevelof eardrum by
placing the probe microphone in the ear canal. Further, the effect
of these PMS on hearing was evaluated by comparing the distortion
product otoacoustic emissions and high frequency pure tone
thresholds (from3 kHz to 12 kHz) of individuals whousePMS to that
of age matched controls who did notusePMS. The relationship between
output sound pressurelevelsand hearing measures was also evaluated.
In Phase I output SPLs produced by the PMS were measured in three
different conditions - a) at volume control setting that was
preferred by the subjects in quiet b) at volume control setting
that was preferred by the subject in presence of 65 dB SPL
busnoisec) at maximum volume control settings of the instrument. In
Phase II pure tone hearing thresholds and DPOAEs were measured.
About 30% of individuals in a group of 70 young adults listened to
music above the safety limits (80 dBA for 8 hours) prescribed by
Ministry of Environment and Forests, India. Addition of busnoisedid
not increase the preferred volume control settings of the subjects
significantly. There were no significant differences between the
experimental and control groups for mean pure tone threshold and
for mean DPOAE amplitude comparisons. However, a positive
correlation between hearing thresholds and musiclevelsand a
negative correlation between DPOAE measures and musiclevelswere
found.
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navigationIntroduction
There are growing concerns overnoise exposureviapersonalmusic
systems (PMS)useby young adults. It is said that with the massive
growth in popularity of portable MP3 players,exposureto highnoise
levelshas increased, and millions of young people are potentially
putting themselves at risk for permanent hearing loss every time
they listen to their favorite music. As no evidence-based
definition exists for hazardous soundlevelsof music, as a
substitute, standards forexposureto occupationalnoisehave been
proposed foruse. [1] The ISO 1999 standard for occupationalnoise[2]
defines a time-weighted average (TWA)levelof 85 dBA for an 8 hour
period per day as the maximum permissible dose of sound energy. The
limit 85 dBA is not fully harmless, as a few percent of people may
still incur a permanent hearing loss if exposed to it. The ISO
standard recognizes that there is a tradeoff between
theexposuretime and the soundlevel, which is quantified by a '3 dB
exchange rule': Every 3 dB increase in theexposure levelmust be
compensated by halving theexposuretime to keep the risk constant.
This means that an 8 hourexposureto 85 dBA bears the same risk for
hearing loss as 4 hours ofexposureto 88 dBA, or a 2 hourexposureto
91 dBA, and so on. In India, the Ministry of Environment and
Forests [3] has proposed a TWAlevelof 80 dBA for an 8 hour period
per day as the maximum permissibleexposure.
Early studies by Wood and Lipscomb [4] and Katz et al., [5]
looked at the maximum outputlevelsproduced by thepersonalcassette
players through headphones. These investigators reportedlevelsas
high as 124 dBA and 110-128 dBA respectively for compact disc (CD)
and cassette players. Based on these reports both the papers
concluded that CD and cassette players produce soundlevelsthat are
hazardous to hearing. However, these reported outputlevelswere
measured at maximum volume control settings which do not represent
the everydayusesettings. Moreover these measurements were made on a
9BS 9A coupler. Other researchers [6],[7] asked users to set the
volume controllevelto their preferred setting and measured the
outputlevels. Results showed that outputlevelswere substantially
less than what is reported by Wood and Lipscomb [4] and Katz et al.
, [5] but even so a significant percentage of people set the
listeninglevelshigher than the permissiblelevelof 80 dBA. Fligor
and Cox [6] recorded the outputlevelsof the different commercially
available CD players in combination with a variety of earphone
styles on a KEMAR. They concluded that outputlevelsvaried across
different manufacturers of CD players and style of the earphone.
But generally smaller insert earphones produced sound
pressurelevelshigher than the permissible limits compared to bigger
headphones. Outputlevels fromPMS have been reported to be as low as
approximately 80 dBA [9] to as high as 121 dBA. [8] Airo et al.,
[10] measured the outputlevelsofpersonalcassette players in an
acoustic coupler at maximum volume control settings, comfortable
volume control settings in quiet and in the presence of
backgroundnoise. They reported thatpersonalcassette players were
able to produce high soundlevelsbut the typical
listeninglevelschosen by the users were not alarming. The
outputlevelson average exceeded 85 dBA when the backgroundnoise
levelwas 72 dBA, potentially creating some hearing loss risk when
cassette players are used in noisy conditions at work or among
traffic. Hodgetts et al., [11] measured the preferred
listeninglevelsfor a MP3 player in normal hearing adults. Using
probe microphone measures, Hodgetts et al., [11] measured the dBA
weighted sound pressurelevelsproduced by a commercially available
MP3 player for different types of earphones (ear bud, over-the-ear,
and over-the-ear withnoisereduction circuitry). Preferred
listeninglevelsrangedfrom75-78 dBA for different types of
earphones. Preferred listeninglevelswere higher for the ear bud
style of earphones compared to the over-the-ear style. Furthermore,
preferred listeninglevelswere increased by 6-10 dB when
backgroundnoisewas introduced to the listening environment to
simulate the 'real world' situation. Torre [12] measured the output
SPL of PMS in the ear canal of 32 participants at four loudness
categories: Low, medium, loud and very loud. Their results showed
that mean output SPLs values were 62, 72, 88 and 98 dB SPL for low,
medium, loud and very loud categories respectively. Based on these
measurements they concluded that output SPLs produced by PMS at
medium or loud volume control settings may not be hazardous as most
of the subjects reported they listen to music at these volume
control settings for about 1 to 3 hours a day.
Meyer-Bisch [13] found significantly poorer pure tone thresholds
in people using PMS longer than 7 hr/week than in the matched
control subjects. Lepage and Murray [14] measured the transient
evoked otoacoustic emission in 700 individuals and found reduced
amplitudes of these in individuals with a positive history ofnoise
exposureor PMSuse. Recently, Montoya et al., [15] compared the
amplitude, incidence and spectral content of transient and
distortion product otoacoustic emissions in normal hearing MP3
player users to those of control group who were non-users of MP3
players. Results showed that subjects who had used MP3 players for
greatest number of years and for more hours each week exhibited a
reduction in incidence and amplitudes of both types of otoacoustic
emissions and an increase in distortion product otoacoustic
emission thresholds.
Previous research has shown that maximum outputlevelsproduced by
cassettes and CD players are above the permissible limits. However,
more recent research has shown that output SPLs of newer generation
PMS like iPods, MP3 players at medium or loud volume control
settings are within the permissible limits and may not be
hazardous. However, there is a paucity of data regarding the
outputlevelsand their effect on auditory system of new generation
MP3 players and mobile phones MP3 systems. In developing countries
like India, mobile phone ownership is growing rapidly. About six
million new mobile subscriptions are added every month and three
quarters of India's population will be covered by a mobile network
by the end of 2008. Moreover, the studies mentioned above have been
carried out in Western population and it is known that output SPL
values as well as susceptibility tonoise-induced hearing loss
depends on the race and ethnicity. [12],[16],[17] Hence, it is
important to measure and document the output sound
pressurelevelsand their effect on hearing of these new generation
PMS including mobile phones in different racial/ethnic groups. This
study specifically looked at outputlevelsproduced by newer
generation PMS in an Asian-Indian population, when measured at
thelevelof the eardrum by placing the probe microphone in the ear
canal. Outputlevelswere measured in three conditions - a) at the
volume control setting that was preferred by the subject in quiet
b) at the volume control setting that was preferred by the subject
in presence of busnoiseand c) at the maximum volume control
settings of the instrument. The effect of this new generation PMS
on hearing was evaluated by comparing the distortion product
otoacoustic emissions and high frequency pure tone thresholds
(from3 kHz to 12 kHz) of individuals whousePMS to that of age
matched controls who did notusePMS. Furthermore, the relationship
between output sound pressurelevelsand hearing measures was also
evaluated.
Materials and Methods
Participants
Participants comprised two groups. The experimental group had 70
adults (35 males and 35 females; age range of 17-24 years; mean age
20.5 years) who reported listening to music regularly through their
PMS. A detailed history regarding the PMS and itsusagewas
collectedfromeach participant using a questionnaire [Appendix I]
All the subjects in the experimental group had been using PMS for a
period of over two years. The control group had 30 adults who
never/very rarely listened to music through PMS. Participants in
the control group had their hearing thresholds less than 15 dB HL
at octave frequenciesfrom250 Hz to 8000 Hz. Subjects in both the
groups showed no evidence of occluding cerumen or middle ear
pathology on otoscopy and tympanometry. Furthermore, subjects in
both groups did not report of any history of occupationalnoise
exposureor ototoxic drugusage. Subjects were recruitedfromdifferent
graduate schools in and around Mangalore, a city in south India.
Written consent was obtainedfromall the subjects. The study was
approved by the research review board of the Dr. MV Shetty College
of Speech and Hearing.
Procedure
The study was conducted in two phases. In Phase I output sound
pressurelevels(SPLs) produced by the PMS were measured in three
different listening conditions - at volume control settings
preferred by the subjects in quiet, volume control settings
preferred by the subjects in the presence of background of 65 dB
SPL busnoiseand at the maximum volume control setting of the PMS -
using a probe microphone.
Output SPLs in the presence of background busnoisewas measured
to simulate a real life listening situation. Busnoisewas chosen as
the backgroundnoisesource as our preliminary survey showed that
more than 90% of the participants listen to music while commuting
to the college by bus. To simulate this "real world" listening
condition we measured the SPL at a distance of 2 mfromthe bus
engine (to represent the maximumnoisethat the commuter may be
exposed), inside the bus, using a soundlevelmeter (Quest 1800) and
a microphone (Quest 4180). Thenoisewas measured while the bus was
running in fourth gear (approximately 1600 RPM) and travelling
approximately at 40 kilometers/hour. These conditions represent the
city ride to which listeners are generally exposed. Four
soundlevelmeasurements were done under these conditions and the
averagenoise levelproduced by the bus engine was 65 dB SPL. This
sound source was then digitally recorded and used as the
backgroundnoisesource in the experiment.Noisewas played back
through sound field speakers connected to apersonalcomputer. The
volume of the speakers was adjusted to produce a SPL of 65 dB at
the position of the subject's head. The amplitude of thenoiseat the
position of the subject's head was measured using soundlevelmeter
(Quest 1800) and a microphone (Quest 4180). In Phase II pure tone
hearing thresholds and DPOAEs were measured on these same subjects
and were compared with age matched normal subjects who did notusea
PMS.
Phase I: Measurement of output SPL of PMS
Only the experimental group participated in this phase of the
study. Output SPLs produced by the PMS were measured in the
subject's ear canal using a probe microphone. A commercially
available real ear probe microphone measurement system (Siemens
Unity Ver 2.7) was used for this purpose. Insertion depth of the
probe was 28 mmfromthe tip of the tube to tragal notch. This
insertion depth is the standard insertion depth used while doing
real ear probe microphone measurements in adults. [18] All the
measurements were made with the subject's own PMS and earphones.
After placing the probe tube in the ear canal, the earphone was
placed. Subjects were asked to play one of their frequently played
songs. Output SPLs were measured in three different conditions
by asking the subjects to adjust the volume control to their
preferred listening setting in quietby asking the subjects to
adjust the volume control to their preferred listening setting in
the presence of 65 dB SPL bus noiseby setting the volume control to
maximumlevel. Position of the probe microphone was not changed
between any of the measurements. All the measurements were done in
a semi-acoustically treated room. Ambientnoisein the test
environment ranged between 40-45 dB SPL during the
measurements.
Output SPLs were measured at individual frequenciesfrom125 Hz to
8000 Hz in octave and mid octave intervals. These ear canal SPLs
were converted to equivalent diffuse field SPLs to which an ear was
exposed, by subtracting the transfer function of the open ear. [19]
The transfer function of the open ear was obtained by calculating
the difference between the reference location at the opening of the
ear canal and the probe microphone SPL near the eardrum for a sweep
frequency tone presented at 60 dB SPL. The output SPLs at
individual frequencies were converted to dBA values by adding the
A-weighting adjustment values. The overall SPL in dBA was then
determined by logarithmically adding dBA values at each
frequency.Fromthis data 8 hour equivalent continuous
A-weightednoise exposure(L eq8h ) was calculated following the same
procedures as Williams. [9] This was mathematically
calculatedfromthe equation
L eq8h = L T + 10 log 10 [T/8]
where L eq8h is the 8 hour equivalent continuousnoise exposure,
T =exposuretime in hours, L T =Levelofnoise exposureover the time
period T.
Phase II: Pure tone audiometry and DPOAE
Pure tone audiometry
Pure tone audiometry was done using a calibrated audiometer (GSI
61 with TDH 50 head phones fitted with supra aural ear cushions).
All the subjects were screened at 15 dB HL in octave frequencies
between 250 Hz to 1 kHz. Pure tone thresholds were measured at
octave and mid-octave frequenciesfrom2000 Hz to 12000 Hz using the
modified version of Hughson and Westlake procedure. This approach
was utilized since previous research has shown that frequencies
above 2 kHz are more sensitive tonoise exposureand will get
affected first. [20],[21] Both experimental and control groups
participated in this experiment.
Distortion product otoacoustic emission
Both the experimental and control group participated in this
experiment. A computer based DPOAE analyzer (GSI AUDERA) was used
to record DPOAEs. DPOAEs were recorded for seven pairs of
frequencies in which f2 was at 1031, 1594, 2098, 3152, 4184, 4816,
6340 and 7277 Hz. The f2:f1 ratio was 1.20. [22],[23] In this
article, the DPOAE data is represented with reference to f2. The
L1/L2 was 65/55 dB SPL. Data acquisition lasted for 30 s for every
frequency irrespective of signal tonoiseratio. A frame was rejected
if it exceeded the 30dB SPL rejection criterion or if L1 and L2
differed by more than 2 dBfromthe target values. These test
acceptance criteria and test rejection criteria were selected
because they are consistent with the values that are employed in
clinical settings with this instrumentation. [24],[25],[26]
Subjects sat in a comfortable chair and the OAE probe was
adequately sealed in the external ear canal and otoacoustic
emissions were recorded with the above mentioned parameters. An
intrinsic real ear intensity calibration was used to determine the
quality of the DPOAE probe seal before starting the DPOAE
measurement. DPOAE amplitude and SNRs at each frequency were
measured.
Both pure tone audiometry and the DPOAE testing were carried out
in an audiometric testing room where the ambientnoisewas within the
permissiblelevelsand the testing was done by a qualified
audiologist with a bachelor's degree in audiology and speech
language pathology. The order of Phase I and Phase II was
counterbalanced among subjects to avoid any order effect and there
was a gap of about 15 minutes between the two phases during which
subjects completed the questionnaire. All the statistical analysis
was performed using SPSS (version 13) software.
Results
On average, young adult subjects listened through PMS for a
period of 1.5 hours a day (range: 10 min-4 hours). Most of them
reported that they listened to music while commuting to
college/hometown. Of the 70 subjects, 62 subjects used mobile
phones to listen to music, 4 used iPods to listen to music and 4
used locally made MP3 players to listen to music. As the iPod or
MP3 players were fewer, these subjects were not included in further
statistical analysis. Therefore, the results pertain to mobile
phone PMS only. None of the subjects used cassette players or CD
players to listen to music. All the subjects used insert kind of
headphones to listen to music. None of them reported any symptoms
of temporary threshold shifts like blocking sensation, tinnitus
after listening to music. Though the information regarding the
different manufacturers and models was obtained, it was not used in
data analysis as the main aim of the study was to see if young
adults listen to music at potentially hazardouslevelsand not to
compare the output produced by PMS of different manufacturers.
Phase I: Measurement of output SPL of PMS
PMS used by young adults mainly consisted of mobile phones, and
very few used iPods and locally made MP3 players. [Figure 1] shows
the mean L eq8h at preferred volume control settings for males and
females for mobile phone users. An independent samples ' t -test'
revealed no significance difference in mean L eq8h between males
and females in all three listening conditions tested ( t = 1.43,
0.89 and 0.65 respectively for quiet, in presence of busnoiseand at
maximum volume, p > 0.05). Since there were no statistically
significant differences between mean output SPLs preferred by males
and females datafromboth the genders were combined for all further
analysis.
[Figure 2],[Figure 3],[Figure 4] illustrate the mean output SPLs
at preferred listening settings in quiet, in the presence of 65 dB
SPL busnoiseand at maximum volume control settings for mobile
phones, iPods and locally made MP3 players respectively. The mean L
eq8h were 73 dBA for mobile phones (range: 40 dBA to 93 dBA), 76 dB
for iPods (range: 56 dBA to 86 dBA), and 79 dBA for locally made
MP3 players (range: 70 dBA to 84 dBA), at subject preferred volume
control settings in quiet. Listening in the presence of busnoisedid
not increase the output SPLs significantly. A paired ' t -test' did
not show a significant difference between means L eq8h produced by
mobile phones in quiet and in the presence of busnoise( t = 1.71, p
> 0.05). Statistical analysis was not carried out for the other
types of PMS as the number of instrument users was limited. At
maximum volume control settings the outputlevelsincreased compared
to the subject preferred volume control setting. Paired ' t -test'
revealed that L eq8h produced at maximum volume control settings
were significantly more compared to other two listening conditions
( t = 12.8, 13.2, P eq8h at the preferred volume control settings
obtained in the presence of 65 dB SPL busnoisefor individual
subjects. As can be seenfromthe [Figure 5], a majority of the
subjects (70%) listened to music at less than L eq8h of 80 dBA.
Nineteen mobile phone users, 1 MP3 player listener and 1 iPod
listener listened to music at higher than L eq8h of 80dBA.
Phase II: Pure tone audiometry and DPOAE
Pure tone audiometry
Based on the results of Phase I, subjects in the experimental
group were divided into two groups: Individuals who used PMS at L
eq8h of less than 80 dBA and individuals who used PMS at L eq8h of
more than 80 dBA. Datafromall three types of PMS users are pooled
as the main purpose was to see if listening to music through PMS
causes damage to auditory system or not. ANOVA was done to find out
the significance of difference between mean pure tone thresholds of
individuals who used PMS at L eq8h of less than 80 dBA ,
individuals who used PMS at L eq8h of more than 80 dBA , and
individuals who did notusePMS. ANOVA failed to show any significant
main effect of subject groups on pure tone hearing thresholds in
both right [F = 2.7 (2,98) p >.05] and left ear [F = 1.8 (2,98)
p >.05]. Descriptive analysis showed that none of the subjects
who used PMS had pure tone thresholds more than 25 dB HL in 3 kHz
to 8 kHz region in both ears. [Figure 6] shows the average pure
tone thresholds of individuals who used PMS at L eq8h of less than
80 dBA , individuals who used PMS at L eq8h of more than 80 dBA ,
and individuals who did notusePMS.
Distortion product otoacoustic emission
All the subjects in the experimental group showed normal DPOAEs
amplitudes and signal tonoiseratios (re: Clinic normative values).
ANOVA was done to find out the significance of difference between
mean DPOAE amplitudes and SNR values between individuals who used
PMS at L eq8h of less than 80 dBA , individuals who used PMS at L
eq8h of more than 80 dBA , and individuals who did notusePMS. ANOVA
did not show a main effect of subject groups on means of DPOAE
amplitudes and SNR values at all the tested frequencies in both
ears. [Figure 7] and [Figure 8] show DPOAE amplitudes and SNRs in
different subject groups across different frequencies. Data is
represented with reference to f2. Error bars show 1 SD
variation.
Relationship between L eq8h and hearing measures
To evaluate the relationship between output SPLs and hearing
thresholds Pearson's product moment correlation was carried out
between subjects' pure tone thresholds as dependent variable and L
eq8h measured in presence of busnoiseas the independent variable.
Datafromall the PMS users were pooled for this analysis. The
results are shown in [Table 1]. There was a significant positive
correlation between hearing thresholds at 6000 Hz and exposed
musiclevels, in both ears. Results of correlation analysis
betweenexposure levelsand DPOAE measures are shown in [Table 2] and
[Table 3]. There was a significant negative correlation between
DPOAE amplitudes and dBA L eq8h at 6340 Hz in both ears and at 2098
Hz in right ear. It can be inferredfrom[Table 3] that there was a
significant negative correlation between DPOAE SNR and dBA L eq8h
at 4816 Hz, 6340 Hz and 7277 Hz in right ear and at 4816 Hz in left
ear. These negative correlations indicate that DPOAE amplitudes and
SNRs were lesser in individuals who tend to listen to music at
higher outputlevels.
Discussion
The majority of the young adults studied here used their mobile
phones to listen to music. Of 70 subjects 62 subjects used mobile
phones to listen to music (88.6%), 4 used iPods to listen to music
(5.7%) and 4 used local made MP3 players to listen to music (5.7%).
On average, young adults listened to music through PMS for a period
of 1.5 hours a day. Most of them reported that they listened to
music when commuting to college/hometown. The mean dBA L eq8h at
preferred volume control settings was 73 dBA for mobile phones, 76
dBA for iPods, and 79 dBA for local made MP3 players. These
preferred listeninglevelsare similar to what participants selected
as "sounds best to you" in the Hodgetts et al., [11] study or
"medium/comfortable" in the Torre [12] study. Hodgetts et al., [11]
reported that participants increased thelevelof the music
approximately 6 to 10 dB when either streetnoiseor multitalker
babble was added to the listening environment. But in the present
experiments, with the addition of 65 dB SPL busnoise, participants
did not increase the preferred outputlevels. This discrepancy
between the results of the two studies may be due to intrinsic
differences in the backgroundnoisesource used in each study.
Busnoisewas utilized as a backgroundnoiseas this simulates the most
realistic condition replicating the environment where the majority
of our participants used their PMS in daily life. However, it is
surprising that when 65 dB SPL busnoisewas added, subjects did not
significantly raise the outputlevelsof the PMS. Most likely, this
is due to the fact that all the subjects used insert earphones and
these earphones may have attenuated the busnoisereaching the ear.
As a retrospective experiment we measured the attenuation created
by the earphones on ten subjects who had participated in the
original experiment. [Figure 9] shows the mean attenuation provided
by the earphones. As can be seenfromthe figure, insert ear phones
provided maximum attenuation of about 23 dB around 3 kHz. Due to
the attenuation of mid-frequency busnoise, young adults may not
have increased the preferred volume control settings in the
presence of busnoise.
The majority of the individuals listened to music at an over
SPLs less than 80 dBA even in the presence of 65 dB SPL busnoise.
No evidence based definition exists for hazardous soundlevelsof
music. As a substitute, standards forexposureto
occupationalnoisehave been proposed foruse. [11] In India, the
Ministry of Environment and Forests [3] has proposed a time
weighted averagelevelof 80 dBA for an 8 hour period per day as the
maximum permissible limit. '5 dB exchange rule' has been proposed
by the Ministry of Environment and Forests as a tradeoff
betweenexposuretime and soundlevel. Referencing this criterion
about 30% individuals in a group of 70 young adults listened to
music above the safety limits prescribed by Ministry of Environment
and Forests. This is an alarmingly large proportion as one in three
individuals who listen to music through PMS may be putting
themselves at risk for permanentnoiseinduced hearing loss if
exposed for extended periods of time (years).
However, the results of pure tone audiometry and otoacoustic
emissions showed that there are no statistically significant
differences between pure tone hearing thresholds and amplitudes of
DPOAEs of individuals whousePMSs at L eq8h of less than 80 dBA, ,
individuals who used PMS at L eq8h of more than 80 dBA and those
who don't. Readers should be cautious about interpreting these
results of the present study as
the measurement was done when subjects were listening to one of
their favorite songs and the listeninglevelcannot be generalized to
different kinds of music that individuals may be listening to
during any particular day.all participants in the present study
were young adults and were using PMS for a period of two years or
more. These young adults are less likely to show the signs
ofnoiseinduced hearing loss due to their limited length of
listening time and because of their age.we measured the
outputlevelsin the ear canals of young adults. These results cannot
be generalized to children as outputlevelsproduced in their smaller
ear canals may be significantly more than what is reported in this
study. However, the results of correlation analysis betweenexposure
levelsand audiological measures are interesting. A significant
positive correlation between hearing thresholds and exposed
musiclevelsat 6000 Hz in both the ears suggests that individuals
who listened to music at highlevelstend to have higher pure tone
hearing thresholds at 6000 Hz. A negative correlation between DPOAE
measures at high frequencies andexposure levelssuggest that
individuals who listened to music at higherlevelshad reduced DPOAE
amplitudes and SNRs. It should be noted that all individuals who
used PMS had "clinically normal" hearing thresholds, DPOAE
amplitudes and SNRs and there was no group difference between these
measures among individuals whousesPMSs at L eq8h of less than 80
dBA , individuals who used PMS at L eq8h of more than 80 dBA and
those who don't. Miller et al., [27] reported that amplitudes of
DPOAEs are more sensitive tonoiseinduced hearing loss than pure
tone hearing thresholds. Our results show that listening to music
through PMS at preferred volume control settings for a period of
two years may not result in "clinically significant" elevation of
hearing thresholds or reduction of DPOAE amplitudes and SNRs. The
correlations between outputlevelsand auditory measures suggest that
listening to music through PMS at higher intensities may cause
subtle pre-clinical damage to the auditory system and over the
years such behavior may be hazardous to hearing. However, these
long-term effects need to be studied through long-term controlled
experiments.
Acknowledgement
Authors would like to thank Dr. T.A. Subba Rao, Principal, Dr.
M.V Shetty college of speech and hearing and management for all the
support.
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AuthorAffiliationAjith Kumar: Dr. MV Shetty College of Speech
and Hearing, Vidyanagar, Mangalore - 575 013
Kuruvilla Mathew: Dr. MV Shetty College of Speech and Hearing,
Vidyanagar, Mangalore - 575 013
Swathy Alexander: Dr. MV Shetty College of Speech and Hearing,
Vidyanagar, Mangalore - 575 013
Chitra Kiran: Dr. MV Shetty College of Speech and Hearing,
Vidyanagar, Mangalore - 575 013
Word count:5401Copyright Medknow Publications & Media Pvt.
Ltd. Jul 2009
Indexing (details)
CiteMeSH
Acoustic Impedance
Tests,Adolescent,Adult,Audiometry,Female,Hearing Loss --
epidemiology,Humans,India -- epidemiology,Male,Otoacoustic
Emissions, Spontaneous,Questionnaires,Risk Factors,Time
Factors,Young Adult,Amplifiers, Electronic -- adverse
effects(major),Environmental Exposure -- adverse
effects(major),Hearing(major),Hearing Loss -- etiology(major),Noise
-- adverse effects(major)Title
Output sound pressurelevelsofpersonalmusic systems and their
effect on hearing
Author
Kumar, Ajith;Mathew, Kuruvilla;Alexander, Swathy;Kiran,
ChitraPublication title
Noise & HealthVolume
11Issue
44Pages
132-40Number of pages
8Publication year
2009Publication date
Jul 2009Year
2009Publisher
Medknow Publications & Media Pvt. Ltd.Place of
publication
MumbaiCountry of publication
IndiaPublication subject
Environmental Studies--Pollution,Occupational Health And
Safety,Medical Sciences--OtorhinolaryngologyISSN
14631741Source type
Scholarly JournalsLanguage of publication
EnglishDocument type
Comparative StudyDOI
http://dx.doi.org/10.4103/1463-1741.53357Accession number
19602765ProQuest document ID
203787135Document URL
http://search.proquest.com/docview/203787135?accountid=49910Copyright
Copyright Medknow Publications & Media Pvt. Ltd. Jul
2009Last updated
2013-02-22Database
ProQuest Medical Library
