Having trouble following a conversation in a noisy restaurant? How loud is too loud? Do men’s voices sound clearer than women’s? These questions have become relevant with Delhi and Mumbai being ranked among the world’s noisiest cities with the highest population with hearing loss. Other noisier cities in India didn’t make it to the list simply because they were not reviewed.
Repeated exposure to loud noise or music causes hearing loss, defined has having a hearing threshold below the normal 25 dB (decibel, the unit to measure sound) in one or both ears.
Apart from traffic and ambient sounds in busy cities, listening to unsafe levels of sound on smartphones and exposure to potentially-damaging decibels at rallies, weddings, cinemas, concerts, sporting events and bars can also damage hearing.
How loud too loud
Exposure to more than 85 decibels (dB) for eight hours or 100dB for 15 minutes can make you go deaf, estimates the World Health Organisation. If you have to speak in a loud voice to be understood, background sound is probably in excess of 90 dB (subway train or noisy traffic signal). Using headphones and earbuds exposes you to around 100 decibels (dB), and frequenting clubs and concerts to 120 dB.
When the exposure is particularly loud, regular or prolonged, it can permanently damage the ear’s sensory cells and cause irreversible hearing loss. The risk to hearing depends on the loudness, duration and frequency of exposure, headphone/earbuds use, and family history of hearing loss.
Wired to sound
Listening to uninterrupted and loud music on earphones damages tiny hair cells (nerve endings) that change sound into electric signals in the inner ear. These nerves carry the signals to the brain, which recognises sound.
Earbuds (inserted into the ears) hurt the most as they do not block outside sounds, which prompts users to turn up the volume. Since they fit inside the ear, they blast loud music directly into the ear canal, which causes more damage to the nerve endings in the inner ear than music played out loud. If the person next to you can hear what you’re listening to on your earphones, it’s over 100 dB and too loud.
The American Auditory Society’s ear-buds rule is 60/60 —listen to not more than 60 minutes at a time at 60% of the maximum volume of your device. Hearing loss can occur after four years of daily exposure to 95 dB; and two hours of daily exposure to 100 dB, which means music lovers can have damaged hearing by their mid-teens.
Ringing or “muffling” after prolonged or sudden exposure to loud sound is a sign that your ears need at least 24 hours to recover. Between 15% and 20% people worldwide have tinnitus, but in most cases, the ringing subsides within minutes and hours. Recurrent or persistent tinnitus that last for more than a day indicates permanent hearing damage needing medical attention. Avoid loud environments such as nightclubs if you’ve already had tinnitus and if you can’t, use earplugs or earmuffs.
How to protect hearing
Hearing loss usually creeps up, with most people now realising they have a problem till they have lost up to 50% of their hearing. What affects hearing? Is it ambient noise – sound of traffic, construction, machines etc – or overuse of headphones and earbuds that blast loud decibels into young ears for hours at a go.
Limit exposure to noisy environments by taking short breaks, using earplugs and ear-muffs and restricting the daily use of personal audio devices to less than one hour say. Use noise-cancelling headphones/earbuds and download smartphone apps to monitor your listening levels. Ensure laws that limit honking and the use of loudspeakers, concerts and construction after working hours in your neighbourhood.
Back to sound
The good news is that hearing, especially in young people, improves if they stop abusing their ears. And we must. More than 5% of the world’s population – 360 million people – has disabling hearing loss (328 million adults, 32 million children), estimates the WHO, with one in three people over 65 years being affected. While there is no data for India, US data shows hearing loss has gone up by 33% in American teens over the past two decades. Those with permanent hearing loss must use hearing aids, cochlear implants, and other assistive devices to ensure their life and that of others around them doesn’t suffer because of this sensory deficit.
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