| Informational Service Article |
| Excerpt ... |
| From iPod to I Can't Hear You: Protect Your Child's Precious Hearing |
“Can you hear me now?” While most people recognize this catchphrase as the slogan of a national cell
phone provider, it may well be a generational motto soon uttered by many of today’s kids.
Why? Because the prevalence of personal listening devices is growing exponentially, and with it grows
the risk of noise-induced hearing loss (NIHL), especially in children. Dr. Anthony Magit, of Rady Children’s
Hospital, says studies estimate that 12% of children between the ages of 5 and 18 years of age show
symptoms of noise-induced hearing loss. This translates into 5 million children in the United States who are
afflicted by this often-preventable condition. Could your child be at risk? The threat is real and may be right
inside your own home.
To understand how personal listening devices such as iPods, MP3 players, and even the old-school
Walkmans can put a child’s hearing at risk, one must first understand the mechanism of hearing. While most
people associate the sense of hearing solely with the ear, the process is far more complex.
Sound is carried via vibrations called sound waves. When these vibrations enter the ear, a small set of
bones (the hammer, anvil, and stirrup) and the eardrum amplify the vibrations, which in turn move minute hair
cells. The vibrations of the hair cells are converted into nerve impulses. The brain picks up the signal of these
nerve impulses and translates them into audible sounds we recognize.
Two principles are involved in the phenomenon of sound. One is frequency, often referred to as pitch,
which determines if a sound is considered high (like a beep) or low (like a bass). The second is the strength of
the sound wave. This is called amplitude, more frequently referred to as volume.
Both frequency and amplitude play critical roles in hearing. But it is the level of amplitude, and its
duration, that are of particular concern when it comes to noise-induced hearing loss. Safe listening practices
are determined by calculating both level of amplitude and duration of sound. These criteria are inversely
proportionate, meaning that quieter sounds can be safely tolerated for longer time frames, whereas louder
sounds have a much shorter window before hearing loss occurs.
Output of sound is measured in decibels. The decibel system is a complex formula involving algorithms
used to determine the amplitude (or volume) of sound. Healthy humans with normal hearing can perceive
sounds from just above 0 decibels (dB). An insect buzzing varies from 3-20 dB. Average conversational
speech measures approximately 60 dB. Heavy city traffic noise registers around 80 dB.
Most experts consider any noise above 85 dB as having the potential to cause hearing loss. Power tools
emit approximately 110 dB. Planes on a runway register 120 dB. And pneumatic jackhammers come in at a
whopping 125 dB. At 130 dB, sound is loud enough to cause physical pain.
Because many modern day personal listening devices can have a maximum amplitude of 120dB, (well
above the safe threshold of 85 dB) parents should be very concerned about the risks to their child’s hearing
from the use of these devices.
It is critical for parents to become familiar with these levels in order to set sensible limits in the use of
personal listening devices. A study by Fligor and Cox (2004) evaluated the risk of noise-induced hearing loss
from the headphones of various personal listening devices. The study not only documented the risk of NIHL
from these devices, but also set guidelines for safe listening practices.
The study recommended a 60/60 rule. In order to preserve healthy hearing, personal listening devices
should be used for no more than 60 minutes a day at 60% volume. This guideline is becoming the industry
standard for safe usage of personal listening devices, and parents should rigorously enforce it.
Manufacturers of these devices are facing increasing pressure, both from the medical and legal
communities, to make their products safer. In March 2006, Apple began offering new software that allows
parents to permanently set the maximum volume level on Apple personal listening products (www.apple.
com/sound) ...
| Published in San Diego Family Magazine June 2007 |
| ** Copyright 2007 Mary Hay Davis ** All rights reserved. No work presented on this website may be reproduced without prior written consent |
