Acoustics Documentaries on Netflix

Happy New Year’s Eve! Have you made any resolutions? Perhaps a resolution to learn something new in the new year? If so, you’re in luck! I’ve recently run across a number of different Netflix documentaries that touch on differents aspects of acoustics that readers of this blog might enjoy. (Yes, I’ve spent a lot of my winter break watching documentaries. Why do you ask?)

Netflix-new-icon

Sure, I guess they have, like, movies and stuff, but really I’m here for the documentaries.

  • Sanrachna (Hindi with English subtitles)
    • This series focuses on the architecture of ancient India. The second episode is all about the architectural acoustics of Golconda fort and Gol Gumbaz. Through careful design and construction, a handclap in the foyer of Golconda fort can be heard half a mile away!
  • The Lion in Your Living Room (English)
    • This Canadian documentary is about domestic house cats. In addition to some discussion of the ins and outs of cat’s ears, there’s a really cool segment by Karen McComb where she talks about the acoustic qualities of different types of purrs.
    • Bonus: Some sweet examples of the Canadian vowel shift.
  • Ocean Giants (English)
    • This BBC documentary about whales and dolphins has three hour-long episodes, and each includes a lot of underwater acoustics and animal communication. If you’ve only got time for one episode, the third episode “Voices of the Sea” is all about whale and dolphin vocalizations.
  • Do I sound gay? (English)
    • This documentary by David Thorpe explores the stereotype of “a gay voice” and does include some cameos by linguists. From a sociolinguisitcs standpoint, I think it’s a bit simplistic (to be fair, probably becuase I’m a sociolinguist) but it’s still an interesting discussion of speech and identity.
    • Bonus: If you want to get a more linguistics-y perspective, this post on Language Log (and the comments) go into a lot of depth.

Oh, and if you don’t have Netflix, I’ve got you covered too. Here are two Youtube channels with linguistics contents you might like:

  • Lingthusiasm (English)
    • This is a brand-new podcast by Gretchen McCulloch and Lauren Gawne (two of my favorite internet linguistics people), and it’s a ton of fun. You should check it out!
  • The Ling Space (English)
    • This channel has been around for a while and has little bite-sized videos about a range of linguistics topics. They have a new video every Wednesday.

Do you know of any other good documentaries about linguistics or acoustics? Leave a comment and let me know!

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What sounds you can feel but not hear?

I got a cool question from Veronica the other day: 

Which wavelength someone would use not to hear but feel it on the body as a vibration?

So this would depend on two things. The first is your hearing ability. If you’ve got no or limited hearing, most of your interaction with sound will be tactile. This is one of the reasons why many Deaf individuals enjoy going to concerts; if the sound is loud enough you’ll be able to feel it even if you can’t hear it. I’ve even heard stories about folks who will take balloons to concerts to feel the vibrations better. In this case, it doesn’t really depend on the pitch of the sound (how high or low it is), just the volume.

But let’s assume that you have typical hearing. In that case, the relationship between pitch, volume and whether you can hear or feel a sound is a little more complex. This is due to something called “frequency response”. Basically, the human ear is better tuned to hearing some pitches than others. We’re really sensitive to sounds in the upper ranges of human speech (roughly 2k to 4k Hz). (The lowest pitch in the vocal signal can actually be much lower [down to around 80 Hz for a really low male voice] but it’s less important to be able to hear it because that frequency is also reflected in harmonics up through the entire pitch range of the vocal signal. Most telephones only transmit signals between  300 Hz to 3400 Hz, for example, and it’s only really the cut-off at the upper end of the range that causes problems–like making it hard to tell the difference between “sh” and “s”.)

The takeaway from all this is that we’re not super good at hearing very low sounds. That means they can be very, very loud before we pick up on them. If the sound is low enough and loud enough, then the only way we’ll be able to sense it is by feeling it.

How low is low enough? Most people can’t really hear anything much below 20 Hz (like the lowest note on a really big organ). The older you are and the more you’ve been exposed to really loud noises in that range, like bass-heavy concerts or explosions, the less you’ll be able to pick up on those really low sounds.

What about volume? My guess for what would be “sufficiently loud”, in this case, is 120+ Db. 120 Db is as loud as a rock concert, and it’s possible, although difficult and expensive, to get out of a home speaker set-up. If you have a neighbor listening to really bass-y music or watching action movies with a lot of low, booming sound effects on really expensive speakers, it’s perfectly possible that you’d feel those vibrations rather than hearing them. Especially if there are walls between the speakers and you. While mid and high frequency sounds are pretty easy to muffle, low-frequency sounds are much more difficult to sound proof against.

Are there any health risks? The effects of exposure to these types of low-frequency noise is actually something of an active research question. (You may have heard about the “brown note“, for example.) You can find a review of some of that research here. One comforting note: if you are exposed to a very loud sound below the frequencies you can easily hear–even if it’s loud enough to cause permanent damage at much higher frequencies–it’s unlikely that you will suffer any permanent hearing loss. That doesn’t mean you shouldn’t ask your neighbor to turn down the volume, though; for their ears if not for yours!

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.