Why Do Shells Sound Like the Ocean?

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iStock

Kevin in Bentonville, Arkansas, wrote in to ask this question: "Why do you hear the ocean when you put a seashell up to your ear?"

All right, first things first: no matter how much it may sound like the rolling waves, it's not actually the ocean you're hearing in a shell.

Now that we've got that out of the way, what exactly is it that you're hearing? In a word, noise; the ambient noise that's being produced all around and inside you, which you normally don't hear or pay attention to because it's too quiet.

To amplify this noise so you can hear it clearly, you need a resonator. Want to make one on the cheap? Form an O shape with your mouth and flick your finger against your throat or cheek. You should hear a note. Make a smaller or larger O, or change the shape of your mouth, and you'll get different notes. Sort of like this. What you're doing here is letting your mouth fulfill its potential as a Helmholtz resonator, where sound is produced by air vibrating in a cavity with one opening. Different pitches can be coaxed out by changing the shape of the resonating cavity.

The seashell you're listening to—the inside of which has many hard, curved surfaces great for reflecting sound—is essentially doing the same thing you just did with your mouth. The ambient noise mentioned before—the air moving past and within the shell, the blood flowing through your head, the conversation going on in the next room—is resonating inside the cavity of the shell, being amplified and becoming clear enough for us to notice. Just like the various shapes we make with our mouths will produce different pitches, different sizes and shapes of shell sound different because different resonant chambers will amplify different frequencies.

The fact that all shells sound just a little bit like the ocean is purely coincidental. Holding any sort of Helmholtz resonator to your ear will produce a similar effect, whether that object is associated with the ocean or not. Put an empty glass over your ear or even cup your hand over it, and the sound you hear will be just about the same.

Amazon's Under-the-Radar Coupon Page Features Deals on Home Goods, Electronics, and Groceries

Stock Catalog, Flickr // CC BY 2.0
Stock Catalog, Flickr // CC BY 2.0

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Now that Prime Day is over, and with Black Friday and Cyber Monday still a few weeks away, online deals may seem harder to come by. And while it can be a hassle to scour the internet for promo codes, buy-one-get-one deals, and flash sales, Amazon actually has an extensive coupon page you might not know about that features deals to look through every day.

As pointed out by People, the coupon page breaks deals down by categories, like electronics, home & kitchen, and groceries (the coupons even work with SNAP benefits). Since most of the deals revolve around the essentials, it's easy to stock up on items like Cottonelle toilet paper, Tide Pods, Cascade dishwasher detergent, and a 50 pack of surgical masks whenever you're running low.

But the low prices don't just stop at necessities. If you’re looking for the best deal on headphones, all you have to do is go to the electronics coupon page and it will bring up a deal on these COWIN E7 PRO noise-canceling headphones, which are now $80, thanks to a $10 coupon you could have missed.

Alternatively, if you are looking for deals on specific brands, you can search for their coupons from the page. So if you've had your eye on the Homall S-Racer gaming chair, you’ll find there's currently a coupon that saves you 5 percent, thanks to a simple search.

To discover all the deals you have been missing out on, head over to the Amazon Coupons page.

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No, Your Coronavirus Face Mask Does Not Limit Your Oxygen Intake

Face masks are not hazardous to your health.
Face masks are not hazardous to your health.
popartinc/iStock via Getty Images

Unlike countries such as Japan and China that have long since normalized wearing face masks, Americans have had to adjust to a new normal—one in which cloth face coverings are recommended to limit the spread of coronavirus. Having your mouth and nose obstructed, even by a breathable fabric like cotton, has led some to speculate that face masks might impede your oxygen intake or make you breathe in exhaled air—or even lead to carbon dioxide (CO2) poisoning.

Neither is likely to occur. Here’s why.

Both loose-fitting surgical masks and cloth masks are porous. Air can move through the material, but it’s more difficult for a respiratory droplet to pass through, making masks an effective obstacle for infectious germs that would otherwise be released into the air. Wearing a mask might feel like your airflow is reduced, and reduced airflow can lead to hypoxemia (low arterial oxygen supply) or hypoxia (a lack of sufficient oxygen in tissue).

But masks can’t affect that intake level. Instead, they cause a mechanical obstruction that may give the wearer the sensation of having to breathe harder or that less air is being inhaled. The oxygen level is not affected.

The other concern relates to hypercapnia, or too much carbon dioxide in the bloodstream. The condition can cause drowsiness, headache, and, in extreme cases, loss of consciousness. The thinking here is that a mask can prevent exhaled air from dissipating, leading the wearer to rebreathe it. But there’s no evidence that could ever occur. While some CO2 can be inhaled, it’s not in quantities that could pose a threat to healthy mask users. The amount is easily eliminated by a person’s respiratory and metabolic systems. If a mask is worn for a prolonged period, it might be possible to develop a headache, but nothing more.

“There is no risk of hypercapnia in healthy adults who use face coverings, including medical and cloth face masks, as well as N95s,” Robert Glatter, an emergency room physician at Lenox Hill Hospital in New York, told Healthline. “Carbon dioxide molecules freely diffuse through the masks, allowing normal gas exchange while breathing.”

There are exceptions. If a person has lung issues owing to disease or other breathing problems, they should consult with their physician before using a face covering. Masks are also not recommended for anyone under the age of 2.

Additionally, extended wear of N95 masks in a health care setting has been associated with hypoventilation, or a reduction in the frequency and depth of breathing. According to the Centers for Disease Control and Prevention, these masks, which are intended to filter out 95 percent of particles, present more breathing resistance. The CDC advises those in the medical field to take breaks from wearing these masks.

But in healthy adults who wear cloth or surgical masks for limited periods of time, hypoxemia, hypoxia, or hypercapnia is highly unlikely to occur.

[h/t USA Today]