Tuesday, July 3, 2012

It's Never Too Early for Hearing Protection

With the fourth of July upon us and all of the noise from fireworks from the pre-holiday celebrations going on around me, it got me thinking about hearing protection for my toddler.  When my toddler was younger, I was more diligent about protecting his hearing with ear muffs designed for kids.  I used it when I took him to a band concert, when I knew there was going to be a lot of firecrackers and even when my husband would vacuum the floor.  Unfortunately, I have become complacent with his hearing protection.

Listening to a band concert at 7 months old
I began reading about Noise Induced Hearing Loss (NIHL).  There are two types of NIHL, acoustic trauma and gradually developing NIHL.  Acoustic trauma "refers to permanent cochlear damage from a one-time exposure to excessive sound pressure. This form of NIHL commonly results from exposure to high-intensity sounds such as explosions, gunfire, a large drum hit loudly and firecrackers."  Gradually developing NIHL "refers to permanent cochlear damage from repeated exposure to loud sounds over a period of time. Unlike NIHL from acoustic trauma, this form of NIHL does not occur from a single exposure to a high-intensity sound pressure level. Gradually developing NIHL can be caused by multiple exposures to any source of excessive volume, such as home and vehicle stereos, concerts, nightclubs, excessive noise in the workplace, and personal media players."

"When we are exposed to harmful noise—sounds that are too loud or loud sounds that last a long time—sensitive structures in our inner ear can be damaged, causing noise-induced hearing loss (NIHL). These sensitive structures, called hair cells, are small sensory cells that convert sound energy into electrical signals that travel to the brain. Once damaged, our hair cells cannot grow back."

The intensity of sound is measured by decibles (dB).  "On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB."  "An increase of 10 means that a sound is 10 times more intense, or powerful. To your ears, it sounds twice as loud."  Any sound about 85 dB can cause hearing loss.  The Occupational Safety and Health Administration (OSHA) recommends that "noise should be controlled below a level equivalent to 85 dBA for eight hours to minimize occupational noise induced hearing loss."  The National Institutes of Health states that at:

  • 110 dB
    • regular exposure of more than 1 minute risks permanent hearing loss.
  • 100 dB
    • No more than 15 minutes of unprotected exposure recommended.
  • 85 dB
    • Prolonged exposure to any noise at or above 85 dB can cause gradual hearing loss.
How Loud is too Loud?
Decibels Sound Source
150          Firecracker
120          Ambulance siren
110          Chain saw, Rock concert
105          Personal stereo system at maximum level
100          Wood shop, Snowmobile
95            Motorcycle
90            Power mower
85            Heavy city traffic
60            Normal conversation
40            Refrigerator humming
30            Whispered voice
0              Threshold of normal hearing

"Approximately 15 percent of Americans between the ages of 20 and 69—or 26 million Americans—have high frequency hearing loss that may have been caused by exposure to loud sounds or noise at work or in leisure activities."  By the time a child reaches school age, 1 in 20 children have hearing loss in one ear (unilateral hearing loss).  A study published in the journal Pediatrics in June 2010 found that "school-aged children with UHL (unilateral hearing loss) demonstrated worse oral language scores than did their siblings with normal hearing."  

The sad thing is NIHL is preventable.  "Although being aware of decibel levels is an important factor in protecting one’s hearing, distance from the source of the sound and duration of exposure to the sound are equally important. A good rule of thumb is to avoid noises that are 'too loud' and 'too close' or that last 'too long.'"

With my toddler, I have become more aware about the things around him that can be too "noisy."  The Sight and Hearing Association actually publishes an annual list of "noisy toys."  In 2011, 19 of 24 toys tested over 100 dB!  That is louder than a wood shop or snowmobile!  "Until 2009, toy manufacturers were not required to follow any guidelines regarding the sound level of toys. Today, all toys must meet the acoustic standard set by the American Society of Testing and Materials (ASTM) (ASTM F963-08), which states the sound-pressure level produced by all other toys except close-to-the-ear toys shall not exceed 85 dB 50 cm from the surface of the toy.  However, most kids play with toys by holding them or sitting right next to them, not at 50 cm away, which is just over 1.5 feet."

"To protect your children, the Sight & Hearing Association offers the following tips:
  • Listen to a toy before you buy it. If it sounds loud to you, it's too loud for your child.
  • Report a loud toy. Call the Consumer Product Safety Commission or the Sight & Hearing Association.
  • Put masking or packing tape over the speaker on the toy. This will help reduce the volume."
I did a little bit of "unofficial" testing of my son's toys using a meter that I downloaded to my iPhone.  To my horror, I discovered that one of his books that "talk" (you have to push buttons and it reads to you) had a reading of 90 dB.  His toy laptop which sings songs and talks had a reading of 91 dB.  I compared these sounds to my husband's coffee grinder which had a reading of 91 dB.  Can you imagine what these loud noises are doing to my son's hearing?

Toys are not the only hazard that I need to worry about.  As my child gets older, he is going to want to listen to a portable music player like an iPod.  A portable music player can put out 105dB of sound.  "One way to prevent turning the volume up too loud, especially in the presence of background noise, is by using noise cancelling headphones for children. These headphones block out extraneous noise and studies have shown if background noise is reduced persons are less likely to turn the volume up too loud."  Another way to limit the maximum volume coming out of a portable music player like an iPod is to set the volume limit.

After researching this topic, I am now a firm believer that my child does not need toys that make noise. Our world is full of noise that we cannot avoid like traffic, or vacuum cleaners.  I would rather minimize the noise that we can avoid to preserve his hearing as long as possible.  He's got a lifetime of sound that I would like for him to hear.  


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