With the recent July 4th holiday, a few folks were asking me if the noise from the fireworks could cause hearing damage. Any noise can cause problems if it is loud, close and prolonged.
Mammals are born with lots of very tiny and delicate hair cells in their inner ears. These cells help to amplify sound. Your baby's ears are more sensitive than those of an adult. Not only do they have thinner skulls, but they also have a full complement of these little hair cells, so sounds will have full amplification. Exposure to loud noises over our lifetime damages these cells. As we get older the higher frequencies tend to be the first sounds that we lose the ability to hear.
Your baby's hearing actually starts to develop between 24-28 weeks of gestational age. It is thought that the noises they hear are slightly muffled (imagine what it feels like when you are under an inch or so of water). They can certainly hear well enough that they seem to recognize the voices of those who have been talking to them while they were in utero. I am certain that both of my babies knew my voice immediately.
So yes, we need to make sure that we protect our baby's hearing, but the fact is that all of us need to pay attention to loud noises that can lead to hearing loss.
To give you an idea of how loud various sounds are, take a look at the following list:
Whisper 30 decibels
Normal conversation 60
Telephone dial tone 80
Traffic noises from inside a car 85
Bart train 90 (range from 73-99)
Power mower 107
Stereo headset 110
Emergency vehicle siren 110-120
Sand blasting or rock concert 125
Gun shot 140
There are a number of free apps for your smartphone that can act as sound meters. One that my nieces told me about is called Sound Meter
I played around with it the other day in the office when there was a screaming child in every exam room. That meter went right up!
The longer the exposure to loud noises, the more damage that can be done. OSHA has guidelines set for safe exposure on the job.
85 decibels for 8 hours
88 decibels for 4 hours
91 decibels for 2 hours
94 decibels for 1 hour
97 decibels for 30 minutes
100 decibels for 15 minutes
103 decibels for 7.5 minutes
For those of you who recognize a pattern, good for you! For every 3 decibels over 85, the safe exposure time gets cut in half.
Okay, so what do we do with the above information?
I have actually had parents call me to ask if it is okay to take their baby to a rock concert. My "NO" possibly reached 100 decibels.
Even though most babies in this country are given a hearing test before they leave the hospital, it is a good idea to have your child's hearing tested on a regular basis once they are over the age of 3 or 4 (sooner if you have concern.)
When hearing is assessed, there are two different factors that are measured, the frequency and the loudness. The loudness of the sound is measured in decibels. The frequency is measured on the Hertz scale. The lower tones are the lowest numbers. People with the sharpest hearing may be able to hear frequencies ranging from sounds with tones as low as 20 hertz and as high as 20,000 Hertz. A sound higher that 20,000 is known as ultrasonic. Some animals, dogs for instance, can hear much higher frequencies than humans. Human speech tends to fall between 1000-5000. A patient passes our basic office test if they can hear a range of frequencies from 500-4000 at the level of 25 decibels.
Any in-office hearing test has the risk of being inaccurate, especially for patients under the age of 4. I have had a patient who flagrantly failed the test, but when I told them I have a secret question, stand behind them, and whisper, "would you like a sticker?" They usually answered, "yes please."
If you are concerned about your kids' hearing (and remember there is a great big difference between hearing and listening), play a whispering game with them and see how they do.
If we all agree that your child is actually having trouble hearing, the next step will be a visit to an audiologist for a much more accurate exam and/or a visit to the ENT specialist.
Thanks to the ladies at Sound Speech & Hearing for sending information about the following options for hearing protection:
They also shared this excellent link
This post is an update of one that I ran several years ago. That one was prompted by piece that the New York times ran about sound machines in babies' rooms.
That question still comes up once in a while. As long as the sound is on a low setting and not directly up against your baby's ear, you don't need to worry. Just be sensible.
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Friday, July 14, 2017
How loud is too loud? Protecting your baby's hearing.
Posted by Nurse Judy at 9:09 AM