“The Blogsquatcher” – The Archives
October 11, 2007 11:26 PM
Last night on the AARF radio show with Robert W. Morgan, Stan Courtney discussed, among other things, his recordings of a peculiar call known as the Illinois Howl.
You can find the recordings at Stan’s site, but here are some direct links.
These recordings, gathered over a period of two months in the spring of 2006, have some very interesting characteristics.
Skeptics who have heard the files have said that they were made by coyotes. I donʼt think thatʼs the case and I want to use this space to show some of the reasons I donʼt think so.
I think there are some key differences in the Illinois Howls that contrast them pretty well against a coyote call. For one thing, a coyote is a small animal and thereʼs a limit to the lowest frequency sound it can make. Every coyote call Iʼve looked at (andIʼm no expert, but Iʼve seen dozens now) has a fundamental tone of around 600Hz.
Lemme throw up a pic here of a coyote call..Note:
What you should notice right away is how simple the call is. All the lines in the sonogram on the bottom are related to each other mathematically, as they should be because a call is made up of harmonics that spring from the fundamental, so that their value in Hz is always a multiple of the fundamental. So in this call you have a fundamental tone of about 600Hz, then harmonics that come at 600Hz intervals after that. Simple.
Other animals make calls that aren’t quite as simple. Here’s a dog, for instance:
This guy’s call is a bit more complicated because you can see that it starts with more bright orange lines than it ends with. I’m sure you’ve heard dogs howl, and how their tone is all raspy at first, but then it evens out to a smoother tone. Well this is a picture of that. The dog starts with a fundamental tone of about 200Hz and has harmonics that fall in 200Hz intervals after that at the beginning, but then when the raspy-ness goes away, half the harmonics drop away too. You are left with a call that has a fundamental of 400Hz, and then harmonics in 400Hz intervals.
It’s hard to see the 200Hz fundamental at the beginning of the file but it’s there. Yet the reason it’s hard to see that particular note is because it is a subharmonic, a sort of “ghost note” down below the true harmonic (which in this case was 400Hz). Now right here I am at the edge of my knowledge about these things — I vaguely understand them, but I came to this as a recording engineer, and an amateur at that. Anyway, keep in mind that animals have this ability. Humans would have it too if we didn’t learn from an early age to use our voices the way that we do. Some folks with congenital defects or certain injuries will introduce subharmonics into their vocal productions, but it’s not something you or I can do at the drop of a hat,
Now let’s look at a picture of the Illinois Howl:
To me there are a number of strange things going on with this call. First, it’s clearly not a coyote, because it has a fundamental tone of 300Hz. Yet that tone actually can’t be found in the sonograph. That’s weirdness number one. Then, look at the way some of the notes drop out — there’s nothing weird about that because the dog could do that in the example above. But look at how some of the tones seem to slide down independently of the rest. That is very strange to me. You’d almost want to say that this is two different animals calling together, but the Illinois Howl was repeated five times and sounded the same.
There’s more – look at how some of the tones seem to grow together and then join, like two magnets with their attractive sides facing each other. I’ve read that scientists call this a “bifurcation” but dang if I can tell you much more than that.. It’s normal for some animal voices too, except that one of the tones is not related to the fundamental at all. That would make it a non-harmonic harmonic.. and that seems to be contradictory to me.
So it’s weird. Here are the frequencies of that call at 3.5 second mark (rounded to the nearest value):
600Hz 900Hz 1200Hz 1500Hz 1800Hz 2100Hz
That’s pretty straightforward, except that the fundamental note, 300Hz (all the other sare a multiple of 300) is entirely missing.
At about 7 seconds, the call resolves to an ordinary looking 600Hz, 1200Hz, 1800Hz, except that now there’s a 1000Hz sitting right in the middle of it.
I don’t understand any of this and it’s all well over my head. I’m a simple musician, after all — but it looks to me like there are some irregularities here. Certainly I’ve never seen a coyote call that does anything like this, and like I said, I’ve gone looking for them and have seen dozens. Dog and wolf calls have some similarities, but I’ve never seen one with that kind of independent movement nor the non-harmonic harmonic sitting in the middle of it.
Maybe somewhere among my readers there is an interested scientist or amateur nature recordist who knows something that can solve the mystery? If so, please post a comment or send me an email (link to your right near the top of the page..)