Month: October 2016

How loud would a million dogs barking be?

~ Rachael Tatman ~ 1 Comment

So a friend of mine who’s a reference librarian (and has a gaming YouTube channel you should check out) recently got an interesting question: how loud would a million dogs barking be?

Adam Benno French Hounds
Alright now, all together on the count of three… are you even listening? 
This is an interesting question because it gets at some interesting properties of how sound work, in particular the decibel scale.

So, first off, we need to establish our baseline. The loudest recorded dog bark clocked in at 113.1 dB, and was produced by a golden retriever named Charlie. (Interestingly, the loudest recorded human scream was 129 dB, so it looks like Charlie’s got some training to do to catch up!) That’s louder than a chain saw, and loud enough to cause hearing damage if you heard it consonantly.

Now, let’s scale our problem down a bit and figure out how loud it would be if ten Charlies barked together. (I’m going to use copies of Charlie and assume they’ll bark in phase becuase it makes the math simpler.) One Charlie is 113 dB, so your first instinct may be to multiply that by ten and end up 1130 dB. Unfortunately, if you took this approach you’d be (if you’ll excuse the expression) barking up the wrong tree. Why? Because the dB scale is logarithmic. This means that a 1130 dB is absolutely ridiculously loud. For reference, under normal conditions the loudest possible sound (on Earth) is 194 dB.  A sound of 1000 dB would be loud enough to create a black hole larger than the galaxy. We wouldn’t be able to get a bark that loud even if we covered every inch of earth with clones of champion barker Charlie.

Ok, so we know what one wrong approach is, but what’s the right one? Well, we have our base bark at 113 dB. If we want a bark that is one million times as powerful (assuming that we can get a million dogs to bark as one) then we need to take the base ten log of one million and multiply it by ten (that’s the deci part of decibel). (If you want more math try this site.) The base ten log of one million is six, so times ten that’s sixty decibels. But it’s sixty decibels louder than our original sound of 113dB, for a grand total of 173dB.

Now, to put this in perspective, that’s still pretty durn loud. That’s loud enough to cause hearing loss in our puppies and everyone in hearing distance. We’re talking about the loudness of a cannon, or a rocket launch from 100 meters away. So, yes, very loud, but not quite “destroying the galaxy” loud.

A final note: since the current world record for loudest barking group of dogs is a more modest 124 dB from group of just 76 dogs, if you could get a million dogs to bark in unison you’d definitely set a new world record! But, considering that you’d end up hurting the dogs’ hearing (and having to scoop all that poop) I’m afraid I really can’t recommend it.

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Can a computer write my blog posts?

~ Rachael Tatman ~ 4 Comments

This post is pretty special: it’s the 100th post I’ve made since starting my blog! It’s hard to believe I’ve been doing this so long. I started blogging in 2012, in my final year of undergrad, and now I’m heading into my last year of my PhD. Crazy how fast time flies.

Ok, back on topic. As I was looking back over everything I’ve written, it struck me that 99 posts worth of text on a very specific subject domain (linguistics) in a very specific register (informal) should be enough text to train a simple text generator.

Bios robotlab writing robot
Linguisitics is… fun… and… cool. How am I doing so far?
So how did I go about building a blog bot? It was pretty easy! All I needed was:

  • 67,000 words of text (all blog posts before this one)
  • 1 R script to tidy up the text
  • 1 Python script to train a Markov Chain  text generator

A Markov Whatnow?

A Markov Chain is a type of simple (but surprisingly powerful) statistical model that tells you, given the item you’re currently on, what item you’re likely to see next. Today we’re going to apply it to whole words in a text.

How does it work? Basically, for each word in your text, you count how many different words occur after it, how many time each shows up and figure out the probability of each transition. So if your text is “The dog ate the apple.”, then there’s a 50% chance that “the” will be followed by “apple”, but a 100% chance that “apple” will be followed by “.”. You can then use these probabilities to generate new sentences, like so:

  • Input: The dog ate the apple.
  • Possible outputs:
    • The apple.
    • The dog ate the apple.
    • The dog ate the dog ate the apple.
    • The dog ate the dog ate the dog ate the dog ate the dog ate the dog ate the dog ate the dog ate the dog ate the dog ate the dog ate the apple. (This may seem silly, but remember that we’re only looking at two words at a time. This model doesn’t “remember” what came earlier or “know” that it’s repeating itself.)

OK, now for the actual training of the model. If you want to play around with this yourself, all my code and text is up on GitHub here.

  1. First, grab your text. I downloaded all my blog posts as an XML file and used a quick little R script to snag just the text I was interested in.
  2. Next, train your model. I used PyMarkovChain, but you can always write your own if you’re feeling it.
  3. Finally, use the model to generate text.

Alright, now I’ve got (admittedly very, very dumb) little program that kinda knows what I write like when I’m blogging. How well does it do at pretending to be me?

First try:

I’m going to break eye contact, look down at your own personalized ASR system

Well that’s… vaguely disturbing. But also not really very human-sounding, and certainly not something I’d write in a blog post. Let’s give it a couple more tries and see if it does any better.

  • But, if frosting has to have a career where you learned it from Clarice
  • We only perceive the things that our bodies and sensory organs and brains can perceive, and we really don’t care about to tell the sounds in the second part, I was expecting to see whether something is grammatical is to put up a bunch of historical stuff that we’ve all heard about the structure in the arts and sciences were depressed
  • (Which is really interesting–I’d love to learn your language doesn’t make you very, very good a recognizing speech
  • Believe me, I know what you can uncontract them and what’s the take-away
    People with short face syndrome–yes, that’s a classical description of what a language does, along with parallels drawn to another, related, languages
  • Short answer: they’re all correct
  • And those speakers are aware of
  • The Job Market for Linguistics PhDsWhat do you much

Hmm, not so great. The only output that sounded good to me was “Short answer: they’re all correct”. And that was just the exact same phrasing I used in this blog post. No wonder it sounds just like me; it is me!

So it looks like I won’t be handing the reins over to Making Noise and Hearing Things bot any time soon. True, I could have used a fancier tool, like a Recurrent Neural Network. But to be perfectly honest, I have yet to see any text generation system that can produce anything even close to approximating a human-written blog post. Will we get there? Maybe. But natural language generation, especially outside of really formulaic things like weather or sports reporting, is a super hard problem. Heck, we still haven’t gotten to point where computers can reliably solve third-grade math word problems.

The very complexities that make language so useful (and interesting to study) also make it so hard to model. Which is good news for me! It means there’s still plenty of work to do in language modelling and blogging.