Chris Joyce interviews Christopher Clark
Jan. 26, 2002
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CC = Christopher Clark, Director of the Bioacoustics Research Program at the Cornell Laboratory of Ornithology
CJ = Christopher Joyce, NPR Correspondent
CC: My name is Christopher Clark. I'm the director of the Bioacoustics Research Program at the Laboratory of Ornithology. And this is what I do for a living. We started designing these autonomous recording units (ARUs) back in 1995-late 1995. We were motivated to do our own because when we were looking around for people to give us recording systems that could last at months at a time in the ocean -- that is what we were challenged with -- they were extremely expensive. I mean a rental of a single unit was over $50,000.
CJ: Youíre kidding. I donít know of anything that rents for $50,000.
CC: Well, it came with two technicians and you had to get someone that would get out onto a boat -- these were pallets the size of a pick-up truck bed, a metal frame on which you attach a tub full of batteries, a tube with a device that allows you to communicate with the surface of the ocean back and forth, and then another tube that has your recording system in it, so we rented one of these from an oceanographic institution -- a colleague that worked there, and it needs an A-frame to lower it over the side of a ship, etc, etc, so we did that, went back three months later, they got it back, brought it to the surface and it had two quarts of water in it, and I thought -- well, we all put our heads together and said -- I am really fortunate, we have a really good team of engineers and computer programmers that all work as a part of my staff, we said -- $50,000? We could build 10 and we could loose nine and still get our data.
So that was the motivation: How can we do this less expensively? And we ended up putting the entire system in a 17-inch glass sphere -- all of the communications, all of the batteries, all of our recording system. Anyway, this little device here was what was commercially available. It meant we could basically -- it has analog to digital input lines, and it has a library of routines, so we could plug that right in.
CJ: And the idea was that you were going after what?
CC: In this case, we were going after marine mammals, endangered species of whales. And part of the motivation of course is it's expensive to go out to sea, to go to these remote places to record. And if youíre using a two-hour digital audio tape and you have to change the tape every two hours, well that's a little inconvenient, because you're not going to stay around that long and many of these species are so transitory, you just have to sort of wait and listen for a long period of time. In the case of the Northern Right Whale where there are only 300 individuals in the entire population, you have to be in the right place at the right time. And this is the same situation with probably the most extinct species of woodpecker, you have to increase the dynamics of your listening space. You either have to record for a longer period of time or be in many places at once. And so we said, well, let's do it this way. We'll go out. We'll put these little recording systems in remote places and leave them, for months at a time. And once something is sitting on the bottom of the ocean or sitting up in a tree, and it's running off a battery, with a disk drive, that's the biggest moveable part; spinning up the heads and writing to the disk, you're in the recording business. So it's sort of an end of the 20th century tape recorder, if you will.
CJ: So how do you get the information -- let's go back a little bit because no one that's listening is going to know anything about this. You're trying to get the sound of Northern Right Whales; you drop this over the side. How do you get the data back, which is sound, right? Sound is what you're after.
CC: Well, you go out to the place where you left [the ARU]. And we have a system where you communicate with it from the surface and you give it a special code and it recognizes the code and it communicates back with you with its own code and says 'I hear you.' And you give it another little command and you say 'please throw a switch' that is just like a light switch and it'll send current down a wire and that wire is connected to an anchor. And when you send the current down the wire that is in contact with the sea water it corrodes the wire in about two minutes and [the ARU] releases from the weight and comes back to the surface. So those devices we call "pop-ups." And then along came a number of obvious situations, for example remote terrestrial habitats, where this technology would be fantastic. To put in remote terrestrial habitats where the chances of you and I going out there on any given afternoon, evening, morning, and night, and turning on a tape recorder with a microphone, and having the bird or the tiger or the elephant come by and make a sound, the chances of that happening are very remote --two hours isn't long enough; six hours isn't long enough.
CC: So the trick was, we can take the same gizmo and instead of an underwater hydrophone we use a microphone. What one of our engineers, Tom Calupca, has done is this little board here is attached to a mother board. And underneath it is layered with a whole series of surface-mounted chips. So what we've done is develop the interface to use the disc drive in your computer as a tape recorder. So when we go back into the woods and retrieve the recording units or go back into the ocean and command them to come to the surface, we open up the PVC tube or the glass sphere and we literally unscrew the disc drive, plug it into the PC, and vacuum off the data. So what we've done is make it relatively easy and inexpensive to go out and put these little listening systems in remote places. And every time you put one of these out you come back with 10, 20, 30, 50 gigabites of raw acoustic material.
CJ: Can you translate that into how many hours?
CC: Well how much recording time is captured all depends on what you're listening for and how fast we were sampling. Now in the case of, for example a right whale, I can put this out and this can record for four months continuously. Since I'm not looking for dolphins and echolocation signals, I just set this up so it's just listening for the right whales. In this case I'm down in the low frequency band, and that saves us the trouble of having all that high sound recorded. Now in the case of a woodpecker, we sample 10 times faster, so our ears are listening to a much greater diversity of sounds because the woodpecker sounds cover a greater variety of frequencies, the sound pitches.
When we record for the whales we really only record the bass clef. Itís like having a chorus and you only record the base. When you're in the woods, with woodpeckers and with birds that are singing, you need the whole chorus, you need to record the whole symphony. That way, bass all the way up to the sopranos, you record the whole thing. So you're recording all of the notes on the piano, not just the ones on the far left. And that's what we have to do with the woodpeckers. We have to get their entire repertoire because we donít want to miss any possibility of getting whether they're drumming on a tree or whether they're doing a flight call or whether they're doing a mating call. So it's the whole spectrum of sound.
[The ARU is] just a little laptop. And of course these things, now, you can get them in 50 gigabites, and they cost a couple hundred bucks.
CJ: So you just have one of these in a pop-up or several?
CC: Each pop-up just has one of these electronic systems.
CJ: But theoretically you could put several in and get yourself six months, a year?
CC: Yes. Now youíre running into the other limiting factor. And that is how big is your battery? How long, how many hours of life do you have in your battery? Now in this expedition we just went to a store and bought a big car battery and juiced it up and that's going to last for 52 days. Now in other cases youíll say -- think if we were in Madagascar, or some really remote place that took us three weeks to hike into and we were looking for some endangered species of bird or lemur or indri or something. Well, when you get there, you want it to work and you want it to work for a long time. You don't want to have to come back in a month, you want to come back in six months. So batteries, that's our limiting factor right now. It's not the disc drives. Because that's gotten so inexpensive and so effective. So I don't know all the techno gobbledy gook but lithium batteries are getting better and better and better. We tried using them underwater and when you had a teaspoon full of salt water you had internal fires. We had one of those situations. The pop-up came to the surface, flipped over and blew up.
CJ: Wow. Because of the battery?
CC: The lithium batteries ignited when they came in contact with water. But now lithium batteries can be immersed in salt water and not explode. So the technology is advancing.
CJ: By the way, on the right whale you're trying to record its sounds. So what do you get from that information or usefulness?
CC: Well, one of the really simple questions is: are they there? So say we went out and we had 50 of these little devices we could sprinkle over a whole range of right whales' known habitat. We could go from Florida past Georgia, all the way up by Hatteras and end up in the Gulf of Maine. We know they're not there all the time. In fact we don't know where half the population is half the time. So you want to go to these places and let them record and the simple question is, are they even there, yes or no. Like the indri [lemur]. Or some of these endangered species of birds. I know people who are interested in cats. Where they know that the cats are disappearing from their habitats, and they think they have some idea that they're still around but they don't know the density. So it's simply presence or absence.
CJ: But with a single listening device you'll know that it's somewhere near, within a set distance that you can guess at or know by the sensitivity of the microphone. But you need two or maybe three or four arrayed to really pinpoint a location. Is that in the works?
CC: Yes, we do that actually. We do that for example with the right whale. So when we set out this system that we have, right now there are six of them operating in Cape Cod Bay and this week I'll go out and put another six out off of the Georges Bank. So we'll use them in a combination where they are close enough to each other that the whale making a sound is heard on all of the units, so we might have four in an array, as it's called. And that way, the same whale is heard on four different microphones and we can triangulate. So we can not only pinpoint where the animal is, but when there's more than one animal we can actually count. For example, on any given opening of this acoustic shutter I can tell you I've got six whales here. Now they might all shut up and not say a sound for another half an hour, and I can't recognize them as individuals, but I can always come up with a minimum count. Very similar to the way people do point counts in terrestrial surveys. You go, you listen or you look for a set time and you make an estimate of the species and what you hear.
CJ: Not dissimilar from what the navy does to find submarines.
CC: And a lot of it's very similar.
CJ: Do they have any problem with you putting it down on the ocean floor?
CC: No. And when [the ARUs] have been put in a strategic place I let them know that. For example, we've been working with some researchers off of Scotland. And thereís a trough between the Shetland Islands over to the Farrow Islands, which used to be a phenomenal whaling ground, very very rich, highly productive ocean system there. And that's a strategically sensitive area because it's one of the avenues into and out of the Norwegian Sea. And we're there monitoring for blue whales and fin whales and humpback whales. But when you hear those species and they're very very low frequency, you hear other things, like submarines. But when we do the analysis we're looking for the voice of a blue whale, we're looking for the voice of a right whale.
CJ: But it's not broad spectrum. In other words you've cut out all of these things enough so that you're not going to be getting a lot of clutter from other things. That's in the sampling rather than in the analysis at the back end.
CC: Actually both. When you set this up and you go put it in the woods or in the bottom of the ocean, you define what you're listening for. And one of the reasons we do that is that it saves disc space, which allows us to have it out there for a long time. So for example we put these in the Mediterranean or off of the Shetland Islands, or for right whales I'll sample at 1000Hz, a thousand times a second, because I know that most right whale sounds are below 500Hz. and I also know that if a right whale is going to make any sound at all it's going to make its contact call, which is between 100Hz and 300Hz, so it's from one of the low notes on a piano to, I donít know what 300Hz is on a piano. 440 is an A. 220 would be the octave below that. So it's somewhere in that low register. So the challenge is, you get back this 30 gigabites of data or 60 days or six months and in this continuum of sound you've got to find the sound that you're interested in. Now in the old days, when you come back with maybe a hundred hours of tape, you sit down and you slog your way through it, convert it into a visual image, a spectrogram, and you look at it on a computer screen or some instrument and you just watch it go by. But now you have 24 hours a day or 8 hours a day, whatever it is, you have thousands of hours. But our challenge now is not so much in collecting the data but knowing how to process it so you only pay attention to the sounds of interest. So it's now detection and classification and recognition.
CJ: So you were doing this with whales. How'd you get into woodpeckers?
CC: How'd I get into woodpeckers? Well, that's a very different species. Well there was this whole interesting crescendo, if you will, of enthusiasm and excitement about this possible re-sighting of the ivory-billed woodpecker here in the Pearl River area Ö Here was this sighting and this possibility and everybody's all excited about what are we going to do, what are we going to do? And I had these gizmos and I stood up at a meeting and I said, hey listen, we can produce these things. We don't have to produce them in 1s and 2s, we can produce them in 10s and hundreds. So lets go put them in the swamp. Let's see what happens. Because there's no way you're going to get someone to sit out there in a swamp for 60 days continuously in one place, and with this we can put 10 out, we can put 20 out, we can cover a huge area. So I sort of put out this challenge, and John (Fitzpatrick, director of the Cornell Lab of Ornithology) turned around and said, "OK, do it." So that's what we did.
CJ: And you had no idea what the swamp would be like, what the conditions would be like?
CC: No, no no. We were just riding blind here. Now, one of the fellows at the lab, Ken Rosenberg, got his Ph.D. at Louisiana State University and worked down here. So he knows Louisiana, he knows the whole area. So at least Ken would describe these swamps that now we've just been in. But until you experience it, it's not quite the same. He'd say, oh yeah, you drive down Route 59 and you might go a hundred meters into the underbrush but you probably wouldn't go much further than that. And then John comes back and shows us those big topo. maps and the aerial photo maps and says we gotta get into there. And you're going, hmm, that's how many miles from the nearest road? So that was the challenge. So they came down here in January about a month ago and reconnoitered around, came back with pictures, and John was totally wired. He was saying, "Oh, found some great spots, we've got to do this, this, and this." But that's part of the excitement of all this, is putting the technology together with the environmental challenge and merging the two and then saying hey, we can work together to really make a difference.
CJ: In a sense there's two tracks right now going on with the woodpecker. I mean you've got the Zeiss team which is doing the old-fashioned way: Let's go out, let's look around, look for habitat, let's be quiet and listen, all the little tricks of the trade of ornithology. You've got this, which is nice to work hand-in-hand. It more than doubles the coverage. So where would you put your money? If it's going to be found the old-fashioned way or this way?
CC: Well, it's going to be a combination of both. So say we come back with 12 of these things in two months. We download all of this data, which is basically having a huge acoustic library of raw material. And my shop, we know how to deal with these large amounts of data. And we can process it and we can go in there and say, here are chunks where we have woodpeckers --and we have folks around who can tell every species of woodpeckers really easily -- and here are some things that are sort of interesting, suspicious, what are they? That's where you need the Zeiss team, that's where you need the experts, the folks that have spent decades working on these birds. We also have, luckily, in the Library of Natural Sounds, we have the recordings from the 1930s of these birds, the only recordings that are on record. So we know what some of these individuals sounded like, and presumably they haven't changed their voices in this time period. So we have something to compare it to. But the definitive answer to whether you do or do not have an ivory-billed on any one of these units is going to require an expert. And I see this as really a totally collaborative kind of approach.
CJ: Well, has it turned out to be basically what you expected? Are you surprised by anything, trying to pull this off? I mean you've had two days so far.
CC: I wouldn't say I'm really surprised by anything. I'm awed by just the natural wonder of a cypress swamp. I've never been in this type of habitat before. Everything went really really well. I mean all the equipment worked. And Rob McCurdy who came down with us and he's the young engineer who designed and built the microphone system and helped me with testing this, and Tom Calupca, the engineer who built this, we beat on this for the last month because when you're out there you don't want anything to go wrong; you want to just plug and play. And that all happened. Now, we had great weather and Paul Wagner, the guy who got us in there by boat. I kept thinking, what if we didn't have a boat? Man, that would be a whole day and a half hike in there. And that was miraculous. So everything has worked really well. Now the proof is going to be in the pudding. When we get them back in a couple of months, what's going to be on them?