I had a few parents recently reach out with questions about the safety of white noise machines. I decided to update my ‘how loud is too loud’ post. As I was doing a deeper dive to check on any updated research and data, I found out that next Wednesday, March 3rd, is World Hearing Day. Who knew?! The worthy goal is to raise awareness on how to prevent hearing loss and promote ear and hearing care across the world. Perfect timing! |
How Loud is too loud? |
Ear and hearing basics A 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. 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. So yes, we need to make sure that we protect our baby's hearing but all of us need to pay attention to loud noises that can lead to hearing loss. 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. Sounds are measured in decibels. The decibel scale is logarithmic, which means that loudness is not directly proportional to sound intensity. Instead, the intensity of a sound grows very fast. This means that a sound at 20 dB is 10 times more intense than a sound at 10 dB. To give you an idea of how loud various sounds are, take a look at the following list: Whisper 30 decibels Normal conversation 60 Snoo at blue level 70 Telephone dial tone 80 Traffic noises from inside a car 85 Snoo on Orange level 86 Bart train 90 (range from 73-99) Power mower 107 Stereo headset 110 Baby shrieking 100-120 (really? Sounds louder!) Emergency vehicle siren 110-120 Sand blasting or rock concert 125 Gun shot 140 Here is a much longer list from Noise Navigator There are a number of free apps for your smartphone that measure sounds and tell you how loud they actually are. The longer the exposure to loud noises, the more damage that can be done. OSHA has guidelines set for safe exposure on the job. (Obviously infants are not at a workplace, although they do have a job, which is letting you know when they are hungry or uncomfortable) 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. How close you are to the noise is another X in the equation. The closer you are, the more of an impact it will have. Noisy Planet is a fantastic NHI public education program that has tons of great resources, including how the above three factors (loudness, distance, time) contribute to hearing loss. 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. As noted above, the answer for the workplace is 85 decibels for 8 hours. But for communities and the home, the Environmental Protection Agency (EPA) recommends that you limit exposure to noise levels above 70 decibels. SO what about the white noise and bassinets such as the SNOO?A recent study found that: Excessive white noise exposure has the potential to lead to noise-induced hearing loss and other adverse health effects in the neonatal and infant population. So, to no one's surprise, if the white noise is blasting for a prolonged period right near their ears, that could in fact cause damage. But, can we add an element of common sense? If you keep the noise level at 70 dB or less, and make sure to not have it right next to the child’s head (try a few feet away), then white noise at a safe level can be very helpful at creating a soothing sleep environment. The SNOO’s white noise is considered safe for babies’ little ears if you have it on the ‘blue level’, which is 68 to 70 decibels. The Snoo can be set to get louder when the baby fusses and quickly reduces when they calm. The sound on the orange level—when the baby is crying hard—is ~86 decibels. That feels a bit too loud to me, so my preference is that you keep it set on the quieter setting. Another common nursery noise is the Hatch. I had Lauren measure the sound of the one in Elliot’s room. When she turned it up to the maximum volume it measured at 77 decibels. Elliot sleeps with it at the 20% which measures at 47 Play around when the baby isn’t in the room and see how loud the different levels actually go. It is easy enough to measure the various sounds with one of the many apps available. Simply test it! Don’t rely on your own hearing as a guide. Hearing tests Even though most babies in this country are given a hearing test before they leave the hospital, it is a good standard to have your child's hearing tested annually 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. As mentioned, 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 than 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 the basic office hearing 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. When I was working in the pediatricians office, I had plenty of patients who flagrantly failed the standard test. Then I would tell them I had a secret question. I would stand behind them, and whisper, "would you like a sticker?" More often than not, they answered, "yes please." This is a good reminder that there is a great big difference between hearing and listening. On the other hand, some enterprising kids are also really good at “passing” the screening if they can see when the examiner pushes the button or if they can figure out the rhythm of the test presentation. So, if you are at all concerned about your kids' hearing, reach out to your pediatrician or visit an audiologist for a much more accurate exam and/or a visit to the ENT specialist. Hearing Protection Options Sometimes you know you are going to be someplace loud. It is great to be prepared. Thanks to Dr. Melissa from Sound Speech & Hearing for sending information about the following options for hearing protection:
They also shared this excellent link https://www.asha.org/public/ For more information, the CDC recently updated their page on this important topic Giant thanks to Dr. Melissa Wilson for her valuable input! |
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