Why Do Shells Sound Like the Ocean?

iStock
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.

15 Convenient Products That Are Perfect for Summer

First Colonial/Lunatec/Safe Touch
First Colonial/Lunatec/Safe Touch

The Fourth of July is the epitome of summer—and after several months spent indoors, you need some outdoor fun more than anything. Check out these 15 summer must-haves while they’re on sale and save an extra 15 percent when you spend $50 or more with the code JULYFOURTH15.

1. CARSULE Pop-Up Cabin for Your Car; $300 (20 percent off)

Carsule tent from Mogics.
Mogics

This tent connects to your hatchback car like a tailgate mobile living room. The installation takes just a few minutes and the entire thing stands 6.5 feet tall so you can enjoy the outdoors from the comfort of your car.

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2. Mosquito Killer Lamp; $30 (25 percent off)

Mosquito-killing lamp.
Kinkoo

If you just so happen to be one of those unlucky souls who attracts a suspicious amount of mosquitos the second you step outside, you need this repellent lamp to help keep your arms and legs bite-free. It uses a non-toxic combination of LED lights, air turbulence, and other methods to keep the pests at bay.

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3. Super Shield Mosquito Repellent Electronic Watch Band; $17 (57 percent off)

Mosquito repeller watch.
Safe Touch

While a lamp is a great non-toxic solution for keeping bugs at bay, active individuals need a bug repellent that can keep up with their lifestyle. This wrist wearable keeps you safe from mosquitoes anywhere by using ultrasonic sounds to drive them away.

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4. ZeroDark 3-Piece Tactical Set: Flashlight, Lantern, and Headlamp; $20 (66 percent off)

Aduro flashlight set.
Audro

If you want your summer to be lit, this set will do the trick. All puns aside, this trio of LED brightness is perfect for camping fun and backyard parties, or it can be stored in the car for emergencies.

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5. Outdoor Collapsible Cooler and Camp Table Set; $64 (27 percent off)

First Colonial cooler.
First Colonial

Cookouts are easy with this cooler and table set that chills your drink until you're ready to pop it into one of the four convenient cupholders. Bring this set camping or out by the pool for convenience anywhere.

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6. Trident: Underwater Scooter; $550 (21 percent off)

Trident underwater scooter.
Geneinno

If you’ve ever dreamed of better mobility while exploring the water, you’re not alone. The Trident underwater scooter, which raised over $82,000 on Indiegogo, can propel you through the water at up to nearly 6 feet per second, which isn't that far off from how fast Michael Phelps swam in his prime. The battery on it will last 45 minutes, allowing you to traverse with ease.

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7. Go Portable Solar Oven; $119 (14 percent off)

GoSun solar grill.
GoSun

Bake, roast, steam, or broil anywhere you bring this portable oven. Measuring in at just over a foot long and weighing only two pounds, the oven will work in most daytime weather conditions and can hold around 13 ounces of food.

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8. 3-in-1 Waterproof Bug Zapper Lantern; $25 (50 percent off)

3P Experts bug zapper.
3P Experts

Mosquitoes tend to be a big problem at night, partly because it's hard to swat in the dark. This lantern will light the area and zap mosquitos from nipping at you in the process.

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9. Urban E-Skateboard: Basic Version (Orange); $120 (73 percent off)

Urban Rover E-Skateboard
Urban Rover

This e-skateboard is perfect for getting around during the summer. You'll catch a breeze while you’re cruising on the battery-powered platform and won’t break a sweat when you pop the compact board in your bag.

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10. H2 Headlamp: Waterproof, Rechargeable LED Wide 180° Angle Headlight; $37 (26 percent off)

Headlamp from One80Light
One80Light

Camping, car troubles, and sports all pose a problem at night. This LED headlight will light up your surroundings across a 180-degree radius for prime visibility, meaning your outdoor activities won't have to stop when the sun sets.

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11. Whirlwind Cool Bladeless Mini Fan; $22 (63 percent off)

Bladeless fan
Whirlwind

This portable fan comes in a powerful handheld size so you can keep cool while on the move. Unlike other portable fans, this one has a sleek, bladeless design and features three different speeds.

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12. Bladeless Personal Fan; $22 (63 percent off)

Bladeless fan
3P Tech

This bladeless fan won't just keep you cool while you work on your laptop—it also has a built-in rechargable battery that you can use to charge your phone.

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13. MOGICS Coconut: Portable Waterproof Light; $37 (24 percent off)

Mogics portable lamp.
Mogics

This portable light is designed to adapt to your lighting preference. It self-inflates in a few seconds and can bounce, get wet, and set the mood.

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14. Lunatec 1L Hydration Spray Water Bottle; $25 (21 percent off)

Lunatec spray water bottle.
Lunatec

A water bottle can do more than hydrate you. This one has a spray nozzle that can create shower, stream, and mist patterns for doing dishes while camping, sharing a sip without sharing germs, and washing off those muddy shoes after a long hike.

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15. Sport Force Hydration Backpack; $25 (68 percent off)

Hydration backpack.
It's All Goods

Hiking enthusiasts know how important it is to stay hydrated, but carrying around awkward jugs of water is a hassle. This unique hydration backpack can be filled with two liters of water and features a convenient drinking nozzle that extends to the user's mouth. Now, you can replenish those fluids without breaking stride.

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This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links. If you haven't received your voucher or have a question about your order, contact the Mental Floss shop here.

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]