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March 06, 2019 Wednesday 01:37:42 PM IST


Health Monitor

Sir, my child has the headphones on all the time even when he walks, sleeps and travels; isn’t it bad for his ears? Please ask him to stop doing that!

It has been a common demand and question asked in any interview in the recent past and I can understand the significance easily as you seldom find a youngster without either a headphone or an ear bud walking along; it’s just started being a part of them. Here, we need a scientific explanation; I being a music lover myself, need to play it safe and scientific.


The fact is that it’s not the music. It is the loudness, duration and closeness to the ears that make it harmful. But then the lack of awareness of this fact probably has led to a major increase in the prevalence of hearing loss in adolescence and young adults, says a study published in the journal of the American Medical Association in 2011 and that has been a reason for concern.


The loudness is the key factor. When your ears are exposed to loud sound, the hair cells in the cochlea, which are the sensory receptors, get damaged and causes a hearing loss. To understand this, the following is a simple explanation on how you hear. The pinna and the external ear carry the sound that you hear to the ear drum. When the ear drum vibrates, it sets the ear ossicles (malleus, incus and stapes which are in continuity) to motion, which transmits the vibrations into the fluid in the cochlea which causes the hair cells of the organ of corti to be stimulated, which in turn converts the song vibrations to nerve impulses in the cochlear nerve and are then taken to the auditory area of cerebral cortex, the ultimate centre of the brain; it’s then the listener becomes aware of the sound.

(Picture of hearing mechanism)


But then, excessive sound is one of the commonest causes for hearing loss in the world -- from military / industrial and recreational sources. Noise, like any sound, is defined in terms of its frequency (expressed in hertz), intensity (expressed in decibels) and the duration. To have a general idea of the intensity of the sound from some very common sources, look at the table below:


Table 1


And now, to have an idea of how harmful loud noise is, the following table presents the current NIOSH (National Institute of Occupational Safety and Health) and OSHA (Occupational Safety and Health Administration) guidelines for noise exposure. 


Table 2


Coming back to the headphones, listening to high power headphones on a near maximum level for a period of one hour in the gym or during a long commute may exceed the current recommendations and be cautioned as to how simple life experiences can lead to a hearing loss. Avoiding head phone-induced hearing damage is not very hard. It simply requires to change some habits.

1.Turn down the volume: certain people derive pleasure in listening to the music only with high intensity music (pop/metal) to go into a “musical trip” ,which could be detrimental to hearing. 

2. Use noise cancelling headphones which block the external sounds, letting you enjoy music at a lower volume. 

3. Over the ear headphones: increase the distance between the ear drum and the source. 

4. Limit the exposure: One easy thing to remember is the 60-60 rule. Don’t listen at any louder than 60% of maximum volume for any longer than 60 minutes at a time. 


How does loud noise affect the hearing? 

Sometimes when you listen to a very loud sound for a very short time like listening close to speaker or some firecracker nearby, you feel ringing in the ears for a few seconds or minutes and then it goes away. You must realise that there are different kinds of impacts with unacceptable noise, close to you. Unacceptable noise may result in a temporary decrease in hearing, sometimes referred to as auditory fatigue which recovers completely and usually lasts for more than 2 minutes and then completely recovers in less than 16 hours whereas permanent irreversible pathological changes too can occur with noise exposure. The latter is much more common and it’s believed that when the noise insult continues, usually as a part of one’s occupation or as recreation, it turns into a permanent damage. Most of the time the anatomical area of injury is the outer hair cells and supporting cells of the cochlea. Noise induced hearing loss starts in the high frequencies between 3 and 6 kHz, around 4 kHz, and spreads to the neighbouring frequencies 

(Pure tone audiogram typical of noise induced hearing loss)


Do you have tough or tender ears?

Don’t think that all ears withstand noise similarly; there is individual susceptibility too. There are tough ears which withstand noise much more than the tender ears which get damaged easily.


Different studies have proven that noise exposure in your younger days has an effect on your hearing when you get old which is one of the top three common conditions affecting the aging population. It suggests that the effect of the hearing loss may extend long after the exposure has stopped; it even contributes to accelerated presbyacousis, the hearing loss in the aged.


Apart from the headphones, where else do you have to exercise caution 


Single loud sounds like from explosions, blast generated by bursting shells and bombs can lead to injuries to external canal, tympanic membrane (ear drum) rupture and various degrees of neural hearing loss. Apart from these kinds of accidental loud noise exposure, similar to the headphone exposure, there are other recreational noise exposure such as exposure to fireworks during festive season, motor cycle riding, drag racing, sport shooting -- all lead to a similar result. Hobbies such as gardening with lawn mowers and chain saws; powered tools in the workshop; music jockeys; musicians and audience at rock concerts; in various industries; in hospitals, for example, MRI units – may produce sound level exceeding 90 db and hearing protectors are recommended .



Prevention always better than cure 

To decrease the hazards of loud noise exposure, a multi-disciplinary approach incorporating hearing conservation programmes have been set up in all vulnerable settings which include hazard identification, engineering controls, personal hearing protection, monitoring hearing and documentation, health education and evaluation. The basic hearing protective device protects the ears by putting a sound barrier around the ear though they may not remove all the sound; the cheapest and most commonly used protector is a prefabricated ear-plug made of soft plastic whereas more effective ones could be ear muffs.

(Pictures of ear plugs/ear muffs )


How do you treat 


Once the hearing damage has turned permanent and significant, affecting daily routine, hearing assistive devices are the option. Hearing aids are the mainstay of treatment of neural hearing loss, typically recommended for sound amplification in individuals with hearing thresholds of 40 decibels or more. For patients with severe to profound hearing loss in both ears, cochlear implantation is recommended where hearing aids are not beneficial. The criteria for cochlear implants have evolved and broadened to encompass individuals with a greater degree of residual hearing too in the recent times. A cochlear implant restores hearing by bypassing the hair cells and transmits electrical impulses directly to the auditory nerve through surgically implanted intra-cochlear electrode.



Table 1


                                                Environmental sounds


  Stimulus                                                      Sound level (dB)


Rustling leaves                                                          20

Whispers at 6 ft                                                         30

Residential area at night                                         40

Quiet office                                                                 50

Normal conversation                                               60-65

Car noise                                                                     70

City traffic                                                                   85

Lawnmower                                                                90

Subway train at 200 ft                                             95

Hand drill                                                                95-100

Snowmobile                                                               100

Motorcycle                                                                  100

Power mower                                                             105

Jackhammer                                                               110

Power saw                                                                   110

Sandblaster                                                                 115

Maximum volume ear buds                                  85-115

Ambulance siren                                                       120

Loud concert                                                             100-125

Pneumatic riveter                                                     125

Jet engine                                                                  140

0.22 caliber rifle                                                       145

12 Gauge shotgun                                                     165

0.357 Caliber revolver                                                 170-175




Table 2


National Institute for Occupational Safety and Health (NIOSH) and

Occupational Safety and Health Administration (OSHA) recommended

permissible noise exposure levels


                             Sound level

Hours per day        NIOSH (dB)           OSHA (dB)


8                                               85                            90

6                                               86                            92

4                                               88                            95

3                                               89                            97

2                                               90                           100

1.5                                            92                           102

1                                               94                            105

0.5                                            97                            110

0.25                                        100                           115

0                                               112                            --

Dr. Rajesh Raju George

The writer is Senior Consultant & Head of Department, ENT, Rajagiri Hospital, Aluva, Kerala

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