Why can’t dogs choke?

And, a related question, why can they bark but not speak? The answer has to do with one of the things that makes us both human and also significantly more vulnerable, right up there with brains so big they make birth potentially fatal. (Hardly a triumph of effective design.) You see, the human larynx, though in many ways very similar to that of other mammals, has a few key differences. It’s much further down in the neck and it’s pulled the tongue down with it. As a result, we have the unique and rather stupid ability to choke to death on our own food. Of course, an anatomical handicap of that magnitude must have been compensated for by something else, otherwise we wouldn’t be here. And the pay-off in this case was pretty awesome: speech.

Alfred Dedreux - Pug Dog in an Armchair.jpg
All the comforts of agriculture, air conditioning and medicine and he can still breathe and swallow at the same time, the smug pup.

But what does all this have to do with dogs? Well, dogs do have a larynx that looks very like humans’. In fact, they make sound in very similar ways: by forcing air through abducted vocal folds. But dogs have a very short vocal folds and they’re scrunched up right above the root of the tongue. This has two main effects:

  1. There’s a very limited number of possible tongue positions available to dogs during phonation. This means that dogs aren’t able to modulate air with the same degree of fine control that we humans are. (Which is why Scooby-Doo sounds like he really needs some elocution lessons.) We do have this control, and that’s what gives us the capacity to make so many different speech sounds.
  2. Dogs have their soft palate touching their epiglottis when they’re at rest. The soft palate is the spongy bit of tissue at the back of your mouth that separates your nasal and oral cavities. The epiglottis is a little piece of tongue-shaped or leaf-shaped cartilage in your throat that flips down to neatly cover your esophagus when you swallow. If they touch, then you’ve got a complete separation between your food-tube and your air-tube and choking becomes a non-issue.

Some humans have that same whole palate-epiglottis-kissing things going on: very young babies. You can see what I’m talking about here. That and how proportionally huge the tongue is is probably why babies can acquire sign quite a bit before they can start speaking; their vocal instruments just aren’t fully developed yet. The upside of this is that babies also don’t have to worry about choking to death.

But once the larynx drops, breathing and swallowing require a bit more coordination. For one thing, while you’re swallowing breathing is suppressed in the brain-stem, so that even if you’re unconscious you don’t try to breathe in your own saliva. We also have a very specific pattern of breath while we’re eating. Try paying attention next time you sit down to a meal: while you’re eating or drinking you tend to stick to a pattern of exhale — swallow — exhale. That way you avoid incoming air trying to carry little bits of food or water into your lungs. (Aspiration pneumonia ain’t no joke.)

So your dog doesn’t choke for the same reason it can’t strike up a conversation with you: its larynx is too high. Who knows? Maybe in a few hundred years, and with a bit of clever genetic engineering, dogs will be talking, and choking, along with us.

That doesn’t mean that something large or oddly-shaped can’t get stuck in esophagus, though.

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Which are better, earphones or headphones?

As a phonetician, it’s part of my job to listen to sounds very closely. Plus, I like to listen to music while I work, enjoy listening to radio dramas and use a headset to chat with my guildies while I’m gaming.  As a result, I spend a lot of time with things on/in my ears. And, because of my background, I’m also fairly well informed about the acoustic properties of  earphones and headphones and how they interact with anatomy. All of which helps me answer the question: which is better? Or, more accurately, what are some of the pros and cons of each? There are a number of factors to consider, including frequency response, noise isolation, noise cancellation and comfort/fit. Before I get into specifics, however, I want to make sure we’re on the same page when we talk about “headphones” and “earphones”.

Earphones: For the purposes of this article, I’m going to use the term “earphone” to refer to devices that are meant to be worn inside the pinna (that’s the fancy term for the part of the ear you can actually see). These are also referred to as “earbuds”, “buds”, “in-ears”, “canalphones”, “in-ear moniters”, “IEM’s” and “in-ear headphones”. You can see an example of what I’m calling “earphones” below.

IPod Touch 2G Remote Mic
Ooo, so white and shiny and painful.

Headphones: I’m using this term to refer to devices that are not meant to rest in the pinna, whether they go around or on top of the ear. These are also called “earphones”, (apparently) “earspeakers” or, my favorites, “cans”. You can see somewhat antiquated examples of what I’m calling “headphones” below.

Club holds radio dance wearing earphones 1920
I mean, sure, it’s a wonder of modern technology and all, but the fidelity is just so low.

Alright, now that we’ve  cleared that up, let’s get down to brass tacks. (Or, you might say…. bass tacks.)

  1. Frequency response curve: How much distortion do they introduce? In an ideal world, ‘phones should responded equally well to all frequencies (or pitches), without transmitting one frequency rage more loudly than another. This desirable feature is commonly referred to as a “flat” frequency response. That means that the signal you’re getting out is pretty much the same one that was fed in, at all frequency ranges.
    1. Earphones: In general, earphones tend to have a worse frequency response.
    2. Headphones: In general, headphones tend to have better frequency response.
    3. WinnerHeadphones are probably the better choice if you’re really worried about distortion. You should read the specifications of the device you’re interested in, however, since there’s a large amount of variability.
  2. Frequency response: What is their pitch range? This term is sometimes used to refer to the frequency response curve I talked about above and sometimes used to refer to pitch range. I know, I know, it’s confusing. Pitch range is usually expressed as the lowest sound the ‘phones can transmit followed by the highest. Most devices on the market today can pretty much play anything between 20 and 20k Hz. (You can see what that sounds like here. Notice how it sounds loudest around 300Hz? That’s an artifact of your hearing, not the video. Humans are really good at hearing sounds around 300Hz which [not coincidentally] is about where the human voice hangs out.)
    1. Earphones: Earphones tend to have a smaller pitch range than headphones. Of course, there are always exceptions.
    2. Headphones: Headphones tend to have a better frequency range than earphones.
    3. Winner: In general, headphones have a better frequency range. That said, it’s not really that big of a deal. You can’t really hear very high or very low sounds that well because of the way your hearing system works regardless of how well your ‘phones are delivering the signal. Anything that plays sounds between 20Htz and 20,000Htz should do you just fine.
  3. Noise isolation: How well do they isolate you from sounds other than the ones you’re trying to listen to? More noise isolation is generally better, unless there’s some reason you need to be able to hear environmental sounds as well whatever you’re listening to. Better isolation also means you’re less likely to bother other people with your music.
    1. Earphones:  A properly fitted pair of in-ear earphones will give you the best noise isolation. It makes sense; if you’re wearing them properly they should actually form a complete seal with your ear canal. No sound in, no sound out, excellent isolation.
    2. Headphones: Even really good over-ear headphones won’t form a complete seal around your ear. (Well, ok, maybe if you’re completely bald and you make some creative use of adhesives, but you know what I mean.) As a result, you’re going to get some noise leakage .
    3. Winner: You’ll get the best noise isolation from well-fitting earphones that sit in the ear canal.
  4. Noise cancellation: How well can they correct for atmospheric sounds? So noise cancellation is actually completely different from noise isolation. Noise isolation is something that all ‘phones have. Noise-cancelling ‘phones, on the other hand, actually do some additional signal processing before you get the sound. They “listen” for atmospheric sounds, like an air-conditioner or a car engine. Then they take that waveform, reproduce it and invert it. When they play the inverted waveform along with your music, it exactly cancels out the sound. Which is awesome and space-agey, but isn’t perfect. They only really work with steady background noises. If someone drops a book, they won’t be able to cancel that sudden, sharp noise. They also tend not to work as well with really high-pitched noises.
    1. Earphones: Noise-cancelling earphones tend not be as effective as noise-cancelling headphones until you get to the high end of the market (think $200 plus).
    2. Headphones: Headphones tend to be slightly better at noise-cancellation than earphones of a similar quality, in my experience. This is partly due to the fact that there’s just more room for electronics in headphones.
    3. Winner: Headphones usually have a slight edge here. Of course, really expensive noise-cancelling devices, whether headphones or earphones, usually perform better than their bargain cousins.
  5. Comfort/fit: Is they comfy?
    1. Earphones: So this is where earphones tend to suffer. There is quite a bit of variation in the shape of the cavum conchæ, which is the little bowl shape just outside your ear canal. Earphone manufacturers have to have somewhere to put their magnets and drivers and driver support equipment and it usually ends up in the “head” of the earphone, nestled right in your concha cavum. Which is awesome if it’s a shape that fits your ear. If it’s not, though, it can quickly start to become irritating and eventually downright painful. Personally, this is the main reason I prefer over-ear headphones.
    2. Headphones: A nicely fitted pair of over-ear headphones that covers your whole ear is just incredibly comfortable. Plus, they keep your ears warm! I find on-ear headphones less comfortable in general, but a nice cushy pair can still feel awesome. There are other factors to take into account, though; wearing headphones and glasses with a thick frame can get really uncomfortable really fast.
    3. Winner: While this is clearly a matter of personal preference, I have a strong preference for headphones on this count.

So, for me at least, headphones are the clear winner overall. I find them more comfortable, and they tend to reproduce sound better than earphones. There are instances where I find earphones preferable, though. They’re great for travelling or if I really need an isolated signal. When I’m just sitting at my desk working, though, I reach for headphones 99% of the time.

One final caveat: the sound quality you get out of your ‘phones depends most on what files you’re playing. The best headphones in the world can’t do anything about quantization noise (that’s the noise introduced when you convert analog sound-waves to digital ones) or a background hum in the recording.