“Ever heard a tree singing?” asks noted composer and bioacoustician Bernie Krause. “It's 70 kHz,” he adds as he reaches for a CD-R in his spartan Northern California studio (see Fig. 1).
The CD that accompanied Krause's recent book, Wild Soundscapes (reviewed in the December 2002 issue), included singing ants, aquatic insect larvae, and the hair-raising growl of an Amazonian jaguar. The singing sand dunes and the calving glaciers mentioned in the text didn't make the CD, so they were first on my request list as our interview wound down. Nonetheless, I was not prepared to hear the sounds of a tree.
“We were listening for the sounds of bats,” Krause continued, “which are up in the 47-plus kHz range. And we heard a steady signal, very unbiological in the sense of it being from a creature. As we moved closer to this cottonwood tree, the signal level increased. We drilled a little hole in the tree and put this hydrophone in. We had an instrumentation device with us that could record a frequency that high, and we got a signal coming from the trunk of the tree. We couldn't figure out what it was. Then we slowed it down by a factor of seven, to get it down within our hearing range.” As we listened to the tree's music, I was startled by the regularity of its pulse and the subtle rhythmic accents. It was as if we were hearing a recording of a virtuosic percussionist playing woodblocks.
TRY THIS AT HOME
“What we discovered was that during a drought, the cells in the xylem of the tree usually maintain a certain pressure from the water that comes into the trunk of a tree during normally wet seasons,” Krause explained. “When that pressure drops during a drought, the cells automatically fill with air, to try to maintain the osmotic pressure. And when they get too dry and they're pumping in air, they pop. When they pop, they die, and the dead cells form the tree's rings. So, when they pop, they make a noise: we can't hear it, but insects can. And when insects hear multiple cells popping, they're drawn to the tree because certain ones are programmed to expect sap. And when the insects are drawn to the tree, the birds are drawn to the tree to eat. It's all a microhabitat formed by sound.”
FIG. 1: Bernie Krause, seated in the sweet spot of his personal studio. He edits his tracks in the digital domain, but prefers the analog domain for processing.
Krause points out that the world around us holds many surprises, if we would only listen. A microphone, like a microscope or a pair of binoculars, provides a way to experience the subtleties of nature that our unaided sensorial faculties might not fully grasp. This article looks at the working methods and technology used by a number of people who record nature sounds.
“People like me are afraid of technology,” Krause says, “particularly when it comes to recorders. They have no problem using video or digital cameras. We're a visual culture: people develop an affinity to anything visual really quickly. But put a recorder in their hand, and they cannot figure out how to push the record and play buttons at the same time.”
To counter this, in Wild Soundscapes, Krause introduces the reader to a simple, inexpensive listening system: the Radio Shack Stereo Amplified Listener, which lists for approximately $35, and a pair of inexpensive headphones. This system allows even the most technophobic person to experience the natural world in a new way.
The next step is to put a recorder into the system so that you can document what you hear. The list of essentials for any kind of remote recording is fairly short: an audio recorder, a microphone, cables, blank tapes or discs, headphones, and power. Optional items — which many experienced recordists would deem essential — include a windscreen for each mic and protective cases for everything.
FIG. 2: Krause''s main recording rig is very portable. Seen here are his Sony PCM-MI DAT recorder, Sound Devices preamp, and gel cell battery, which can run 18 hours on one charge.
If there's one benefit to the continued miniaturization of recording technology, it's that a quality recording rig can be easily carried almost anywhere. But unlike the sound-effects location recordist, who often needs merely a few seconds or minutes of audio material, the nature recordist works to capture sounds in the long form: those gradually unfolding movements of Mother Nature's symphonies that can only be experienced through patient and attentive listening. Many of these sounds are quiet enough to quickly reveal the flaws of a recording system.
Sound designer Rudy Trubitt notes that the conditions and desired result determine the gear he takes into the field. “It may be advantageous to have a portable or invisible rig. You'll need to ask yourself how much mobility is required and what the power considerations are. For example, what's the smallest rig you can have for hiking when you need lots of batteries?”
The three essential elements of Krause's recording setup are a Sony PCM-M1 DAT recorder, a Sound Devices preamp, and a battery pack (see Fig. 2). Even when you add mics, windscreens, cables, a tripod, and a case, the load is light enough for backpacking (see Fig. 3).
BIOPHONY AND GEOPHONY
In Wild Soundscapes, Krause stresses the importance of capturing the biophony — the collective sounds expressed by an entire habitat of creatures — when recording in what he terms the wild natural. A related term, geophony, refers to the soundscape of nonliving phenomena, such as water, wind, and geologic sounds.
“Natural sound libraries usually focus on individual creatures, which, to me, expresses a kind of 19th-century science: abstracting things from their context. The context tells a lot more about why these creatures vocalize, their vocal mechanisms, and how they learned to vocalize in the first place.
“We tend to deconstruct the natural world around us. When we just take a robin or a sparrow out of context, it's like taking just the strings or the horn lines out of a Beethoven symphony. You can listen to it, but you only get a partial sense of the whole.”
THE INCREDIBLE SHRINKING RECORDER
The first time Krause recorded in the great outdoors was in the late '60s with his partner, Paul Beaver. “Our first record for Warner Brothers was called In a Wild Sanctuary. The mandate from Warner Brothers was to go out and try to find a way to connect sounds of the natural world to the sounds of a synthesizer and to do an album on the subject of ecology. It came about at a very propitious time because Nagra had just come out with their new portable stereo recorder, which allowed us to go out into the field and record in ways that we couldn't have done before. Also, new mic technology allowed us to record in the field without a lot of humidity and wind problems, although the mics were very sensitive. They had a wonderful dynamic range. This explosion of technology increased our capabilities to levels never before imagined.”
FIG. 3: Although Krause''s entire recording rig (including a tripod and 10 meters of coaxial cable) fits into a backpack, it allows him to record for weeks at a time. His pair of Sennheiser microphones is inside the Rycote zeppelin.
Into the '80s, Krause's favorite setup — a rugged, nearly indestructible Nagra IV-S 2-track reel-to-reel recorder, mics, tapes, batteries, and accessories — weighed a hefty 45 pounds. Carrying around such a weighty kit is almost unthinkable today. Besides taking size and weight into account when you choose your field recorder, it's also important to consider the equipment's ability to survive in extreme conditions. Can the recorder be used at an angle and while moving? Will it work while being jostled?
Since the late '80s, portable DAT recorders have been a popular format for field recording, replacing heavier reel-to-reel units and portable analog cassette machines, such as the Sony TCD5. The popular DAT recorders for field recording include the Sony PCM-MI, TCD-D7, TCD-D8, and TCD-D100 and the larger Tascam DA-P1 and HHB PDR1000.
More recently, the tapeless MiniDisc (MD) recorders have gained popularity, as much for their size as for their reliability. That robust optical-storage format is shock resistant and handles heat and dirt fairly well. However, some recordists are wary about Adaptive Transform Acoustic Coding (ATRAC), MD's data compression scheme. “Some people are scared of ATRAC, but they really shouldn't be,” says Trubitt. “MiniDisc recorders are small, inexpensive, and you can carry a spare. By comparison, DAT machines aren't so cheap that you'd want to carry two on your body.”
“The favored MD recorders are the relatively inexpensive Walkman-style ones,” says recordist and frog enthusiast Walter Knapp. “But do your research carefully, because not all models are suitable for field recording.” In the MD field, popular models include the Sony MZ-R30, MZ-R50, MZ-R55, MZ-R700, and MZ-N505; the Sharp 722, MD-DR7, and MD-MT180; the Marantz PMD650; and the HHB Portadisc MDP500 (see Fig. 4). An interesting feature of the Portadisc and the MD-DR7 is a prerecord memory buffer — they store 6 seconds and 5 seconds, respectively — which allows you to capture sounds that occur before Record is fully engaged.
On the PCMCIA front, the Marantz Professional PMD690 shows promise because it has balanced XLR inputs, coaxial S/PDIF outputs, and records in MP2, WAV, and Broadcast WAV formats. At the high end is the Nagra V 24-bit hard-disk recorder, which records in the Broadcast WAV — file format.
FIG. 4: The HHB Portadisc MDP500 is pro-level MD recorder with balanced XLR inputs, unbalanced RCA outputs, and digital S/PDIF I/O. It can be powered by AC or by AA or rechargeable NiMH batteries.
Core Sound (www.core-sound.com) has just announced a series of products that form an inexpensive high-resolution system that may be the answer for recordists looking to replace their DAT and MD recorders. The PDAudio-CF is a Compact Flash S/PDIF interface, with optical and coaxial inputs, that supports 24-bit, 192 kHz recording and can be mounted in PDA hosts (such as the HP/Compaq iPAQ) that run Windows CE/Pocket PC 2002 or Linux or used with laptop and desktop computers running Linux or Windows 2000 or XP. The PDAudio-CF will be priced under $300. Core Sound also offers recording applications, which include metering and WAV-file compatibility, for these PDA platforms. For the front end, Core Sound offers the portable Mic2496, a pro-level battery-powered mic preamp and 24-bit A/D converter. The dual-channel Mic2496 offers 48V phantom power, ganged level controls, a low-battery light, clipping indicators for each channel, and four selectable sampling rates (44.1 to 96 kHz). The company also has its own line of binaural microphones that complement the system.
This is by no means an exhaustive list of potential field recorders. In fact, some of the recorders mentioned above are out of production and are only available secondhand. But because of their features and price, even an older model is worth hunting down if it fits your budget and needs.
USING MICS OUTDOORS
Just as they do in the studio, the mics you use outdoors will shape the sounds you record. Field recordists agree that omnidirectional mics are better in windy situations than directional mics. Otherwise, mic choices are based on a combination of personal preference, job requirements, budget, and field conditions.
For nature recordist Douglas Quin, the choice of gear is determined, in part, as a response to the situation. “I tend to decide on what mics to use when I get a feel for a place and the sounds that I hear. It's much like a photographer, who chooses lenses, filters, cameras, formats, and lighting. The tools need to be appropriate to what you are trying to capture. For ambiences and groupings of animals, I generally use stereo microphone configurations. I also use shotgun microphones and parabolic reflectors for species-specific recordings. Parabolic dishes work well for songbirds, but not for larger animals, where there is a stronger low end.”
FIG. 5: With an XY pair, amplitude alone accounts for spatial positioning in the stereo field, because no time differences occur between pickup by the two capsules. Typically, the angle between the capsules is 90 to 135 degrees.
“There are a number of interesting stereo mic techniques suitable for use in field recording,” Trubitt says. “When I'm choosing one over another, sonic character is obviously a key consideration. It is not, however, the only determining factor. The other issues I consider are creating effective protection from wind noise and ease of maneuverability.” The most common stereo configurations used by nature recordists are XY, M-S, ORTF, binaural, and quasi-binaural.
An XY configuration requires a coincident pair of directional microphones, positioned so that their capsules are as close to each other as possible without touching (see Fig. 5). The angle between the capsules is usually set between 90 and 135 degrees, with the greater angles offering a wider stereo spread. The XY setup gives you a narrower, more focused stereo image than other stereo-miking techniques, but there is often a 3 dB drop in the center of the image. “I often use XY for ambient recordings,” notes Quin, “where I find myself in the middle of a flock of birds or where animals are distributed all around me.”
“You can make your own XY setup using two directional mics, but the result can be a bit ungainly for field work,” Trubitt says. “Creating a suitable windscreen will also be an issue. Individual windscreens will increase the distance between capsules. If you're planning to standmount the pair, the extra bulk may not matter.” The Røde NT4 is a recent example of a stereo XY microphone that addresses these issues.
“This kind of crossed-pair, stereo array provides good localization and imaging,” Trubitt continues. “It's not the most dramatic picture, but it is accurate. My main concern about this technique is the quality and character of the cardioid mics. If the mics have an uneven off-axis response, which is not an uncommon problem, to my ears they can take on a pinched quality. Also, if you point a crossed-pair array directly at the sound source of interest, you are picking it up with the 45 degree off-axis response of both capsules. This may also lead to coloration.
“A pair of crossed figure-8 mics, which is called a Blumlein array, produces a spacious and pleasing stereo image,” Trubitt says. “Although the proximity effect of cardioid and figure-8 mics enhances the bass frequencies when close to the subject, there is an unavoidable bass roll-off when working at a distance. Consequently, I wouldn't choose them for thunder storms or elephant snorts. In contrast, omni microphones maintain their full low-frequency response regardless of their working distance from the sound source, and they are much less sensitive to wind noise than directional mics. From a subjective standpoint, I often prefer the sound of omnis; their off-axis response tends to be smoother than many cardioids.” Several stereo techniques — M-S, binaural, quasi-binaural and spaced pairs — use omnidirectional mics.
FIG. 6: Recording with an M-S stereo setup gives you a number of options. For example, you can change the width of the stereo spread during-post production or use the signals from the individual mics for different purposes.
M-S (middle-side) combines a “mid” microphone, which is the center and is usually a cardioid, hypercardioid, or omni, and a bidirectional “side” microphone, a figure-8, facing sideways. Using an omni in the mid position provides the most open and natural ambience, while a more directional mid mic gives greater focus and isolation to the sounds directly in front of you, at the expense of accurate stereo placement of sounds to either side.
The two capsules are placed as close to each other as possible, with the mid mic's primary axis aligned with the side mic's null axis (see Fig. 6). The M-S system yields a robust stereo image, which you can modify during post-production, and a strong center image. An advantage to the M-S system is that you can reencode the stereo mix into the original middle-side components, provided you haven't processed the signals. You can also use the middle image and side images independently. M-S is thoroughly mono compatible.
In order to get a complete stereo image, the M-S signal needs to be decoded with a sum-and-difference matrix. A number of portable preamps offer M-S onboard decoding, so you can record and monitor a traditional stereo image. In addition, some M-S microphones are able to decode the signal, or you can use outboard hardware or a software plug-in. If you don't decode the signal, you will record the mid mic to one channel (usually to the left channel) and the side mic (usually to the right), which can be disorienting because you won't be hearing the stereo spread that you see in front of you. Any stereo mic with a width switch is probably an M-S model. The Shure VP88 is an example of a single-point M-S mic with a cardioid center capsule and a built-in M-S decoder.
“Because nearly all figure-8 mics are side-address,” says Trubitt, “an M-S pair will be positioned in parallel, perhaps even touching. This compact arrangement is convenient to carry and fits easily in a single shockmount and windscreen combo such as a Rycote blimp. This yields low handling noise and high wind resistance, which is highly desirable for field work.”
“An advantage of M-S,” says Quin, “is that you can adjust the stereo image and enjoy the benefits of having two recordings in one — the mid channel can be a species-specific recording on its own. I also may choose ORTF, because the angle of incidence at 110 degrees can communicate certain spaces with great clarity.”
FIG. 7: The Soundman OKM II K was designed for recording with portable devices. The mics are suitable for use as a binaural headset mic, a boundary-layer mic, or as a stereo clip-on mic.
Another stereo technique is to use a pair of spaced omnis. However, Trubitt notes that recordings made with a spaced-omni pair often lack a strong center image.
Traditional binaural stereo recording utilizes a dummy-head with the mic capsules tucked into anatomically correct dummy ear canals. Another less expensive option is a pair of in-ear mics, such as the German-made Soundman OKM binaural mics (see Fig. 7). These little omnis are foam covered and sit in the ear like tiny Walkman ear buds. A mic pair like this is very portable, is invisible to other people, and creates a stunningly realistic stereo image when auditioned using headphones. Omni capsules are commonly employed in binaural recording, which gives you an improved low-frequency response and better wind tolerance.
Binaural recordings are meant to be heard using headphones; over loudspeakers, binaural recordings have a weak center. Stereo shuffling, a signal process described by Blumlein, can be used to improve loudspeaker playback compatibility. A plug-in, such as the Waves S1, can be used for shuffling.
For better speaker translation, many recordists choose the Crown Stereo Ambient Sampling System (SASS-P) mic. The SASS-P is a roughly head-size — although decidedly not head-shaped — apparatus that provides a quasi-binaural image that is more loudspeaker friendly than a binaural arrangement.
FIG. 8: The ORTF technique, which specifies two cardioid mics 110 degrees apart with 6.69 inches between the capsules, was designed to mimic human hearing.
Binaural and related mic pairs often use omni mics, but you can use spaced cardioid mics as well. “Try a pair of cardioids spaced roughly ear-width apart and angled outward from 110 degrees to 135 degrees,” says Trubitt. “The French body Office de Radiodiffusion Television Francais (ORTF) specifies this arrangement as 6.69 inches from capsule to capsule with an angle of 110 degrees (see Fig. 8). In contrast to crossed-pair XY or M-S techniques, spaced cardioids provide a bit more drama at the expense of precise localization of individual objects in the stereo field.”
Spaced capsule arrangements are generally less mono compatible than coincident techniques such as M-S and crossed pairs. On the other hand, spaced techniques generate a stereo signal that includes time-arrival differences between channels. Coincident techniques only create intensity differences between channels: a sound on the right plays back louder in the right speaker. “I am less likely to use these spaced arrangements in the field,” says Trubitt, “not so much because of mono-compatibility concerns, but because the size of spaced arrays usually requires two shockmounts and two windscreens, making the apparatus ungainly unless I am putting it on a tripod and walking away.”
In his work recording frogs, Walter Knapp uses a Telinga Pro 5 parabolic microphone (see Fig. 9). “A good parabolic mic can move you much closer to the sounds you want. It's the easiest way to be close to the calling frog out in the middle of the swamp. A parabolic can also be used to sort through mixtures of callers, focusing on small groups rather than the entire swamp. And you can cover a lot of area from one spot.” Knapp cautions, however, that the long reach of the parabolic mic will also pick up far-away man-made sounds as well.
“A parabolic,” he says, “gains a lot of its amplification by concentrating the sound before it hits the microphone. You can raise the gain electronically, but you also amplify the built-in electronic noise of the mic. A parabolic can do a good job with a microphone of lower quality (and thus cheaper).” Knapp has experimented with a DIY parabolic mic, which can be seen on his Web site (http://frogrecordist.home.mindspring.com/docs/quickparabolic.html).
Ultimately, when choosing a microphone, you need to know what your power requirements will be (phantom power or plug-in power from the recorder), what kind of recording you want to get, and the environmental conditions in which you will record. In addition, your choice of mics will be gauged in part by other parts of your system, such as your recorder. For example, you need to match the impedance of a mic to your preamp and recorder. If you have a noisy preamp in your MD recorder for example, it's helpful to balance it out with a quiet but high-output mic.
ASSEMBLING YOUR SYSTEM
For the beginner, choosing the right components is difficult because of the wide range of options. “The first thing to remember is that there is no mic-preamp combo that will guarantee a hiss-free recording or a situation where you won't hear some bit of gear-related self-noise,” says Trubitt. “Natural soundscapes can be very, very quiet.” With that in mind, Trubitt offers examples of some of his recording setups, from an inexpensive, highly portable system to a more expensive, advanced setup.
FIG. 9: The Telinga Pro 5 can be fitted with stereo or mono mics, using plug-in or 48V phantom power, depending on the recorder you use.
“My smallest system,” he says, “consists of the Soundman OKM II K Classic Studio binaural mics, which run off of plug-in power. These are plugged directly in to the Sharp MS702 MK MiniDisc recorder, which runs off of a DIY battery pack with two D cells. This setup has the advantage of being hands free and unobtrusive, and when everything's working right, I get hours and hours of recording time. I take this setup to places where recording is not the primary purpose, but where I don't want to miss something interesting that might happen.”
“The major drawback of this setup,” Trubitt continues, “is poor rejection of wind noise, even though the mics are omnidirectional. And any time you use a MiniDisc's mic preamp, it's going to be noisy. In nature recording, machine self-noise is such a pervasive problem: the combination of an electret mic, which is invariably noisier than a true condenser mic, and the consumer front end of a MiniDisc recorder is going to be hissy. It's not a good system if you're trying to record a quiet bird song. And when the mics are on your head, it's difficult to get the right mic placement. You have to keep your head still while recording, and if you're using in-ear mics, you can't monitor the sound to tape by wearing headphones, because you'd get feedback.”
“The next step up is to improve the mic and reduce wind noise. I use the battery-powered Shure VP88, which has a built-in M-S decoder, although you can also record undecoded M-S. I also add a Rycote Windjammer with the optional furry high-wind cover, or a homemade windshield. I put the mic on a boom so I can move the mic around, which is helpful in finding the right place to record” (see Fig. 10).
“Next, I may add an external preamp. I use the Denecke AD-20 Zefiro Inbox, which doesn't offer phantom power and is not a high-gain device, but it's easy to use, inexpensive, and very rugged. It offers XLR connectors and digital outputs. Now I've upgraded the mic, but I'm still using a storage device that uses data compression — MiniDisc. It's still a somewhat noisy setup, but it's good in wind and you can turn your head around without problems.
FIG. 10: Rudy Trubitt records the sound of a chunk of melting ice on the shores of a glacial lake in New Zealand using an Audio-Technica AT835ST in a Rycote windscreen and a boom pole.
“Next let's upgrade the data storage device. I go with DAT, but use outboard mic preamps. The good news is that there is no ATRAC data compression. However, I'm somewhat skeptical of DAT reliability in terms of transport problems and tape handling: I don't consider the format to be bulletproof. What I always do is record a little slate, then rewind it and play it back to make sure everything's working right. With some of the small DAT machines, you may see the tape counter incrementing and meters going, but the machine is not recording a signal. I've made a lot of great recordings on DAT, but I always carry an MD as a spare.
“The long-term prospects of the format are troubling, in terms of replacement parts,” says Trubitt. “I wouldn't buy a new DAT machine.”
A number of nature recordists share these sentiments about DAT technology: although they may currently prefer the DAT format to MD, they're looking forward to the next generation of hard-disk recorders that will be hearty enough to meet the demands of field recording.
FIG. 11: The Grace Design Lunatec V3 adds a 24-bit, 192 kHz converter to the quiet and robust V2 preamp.
“To further improve the system, I would upgrade the mic and preamp. At my top end is a pair of Schoeps — CMC-5 bodies, with either MK-41 hypercardioid or MK-6, 3-pattern capsules, which offers figure-8, cardioid, and omni. I'll use the appropriate size Rycote zeppelin, and a Grace V2 preamp (see Fig. 11). This is a much quieter front end, which allows me to record dawn choruses and get a usable signal. But if it's going to be too wet or humid for the Schoeps, I'll bring the VP88.
“Another setup has Sennheiser MKH-series mics and the Sound Devices MixPre preamp, which may be quieter than the Schoeps-Grace combo. The Sennheiser mics are much more tolerant of humidity.
“For my multichannel experiments, I use the Korg D16, but it takes a lot of effort to power it in the field. And you can't walk around with it. It also opens a can of worms in terms of miking for multichannel recording.
“Someday there's going to be an affordable hard-disk recorder, and I'll be switching to that,” Trubitt says. “I'm not enthusiastic about bringing a laptop into the field, because you can't walk around with it while recording, and you cannot see the screen in the sun without a sunscreen, such as the pop-up one made by Hoodman” (www.hoodmanusa.com).
Krause is very specific about the setup he and his crew use in the field under most conditions. “We use only Sennheiser mics — an MKH 30 and an MKH 40 — because they're low noise and they've got a really nice dynamic range. They're a little bit less sensitive to wind than other mics, and we can take them into habitats that are very humid without failure, unlike other mic systems. We use an M-S system: the MKH 30 is a figure-8 and the MKH 40 is a cardioid. They're mounted piggyback on top of one another” (see Fig. 12).
FIG. 12: Krause demonstrates his M-S stereo microphone setup, which seats a Sennheiser MKH 40 cardioid above an MKH 30 figure-8. The mics can also be mounted on a tripod.
“The Audio Engineering Society did a study on the noise floors of different mics,” says Krause, “and the Sennheisers came out, at that time, as the best. We've not used anything else since.” Krause will often set the mics on a tripod and position himself and the recorder some distance away.
Quin uses Schoeps as well as Sennheiser microphones. “The Sennheisers are workhorses and function well in extreme temperatures. There is also a fullness to the sounds that they pick up. However, I like the high end on the Schoeps, particularly for birds and insects. Ultimately, topography, climate, and the distribution of wildlife help determine the mic choice.”
Quin records to DAT, but, like many recordists, he's keeping an eye on developments in hard-disk recording, particularly multichannel. “For me, the key elements are portability and ease of use.”
Although she used a system similar to Krause's when they worked on projects together (see Fig. 13), recordist and biologist Ruth Happel says she often prefers a more mobile system. “I usually use a Sony D3 portable DAT. I tend to walk around with my equipment, because I find that if I can travel along with animals, I can get a lot more recorded. I'll carry a very small digital recorder and very small mics, which I attach to the top of my vest. In the vest pockets, I carry spare batteries, preamp, and recorder.
“I mainly use small omni mics,” Happel says. “Sony ECM77s, and I use my own windscreens. These mics are great for recording the quiet nuances of sound like the actual shifting of a cricket's legs before it chirps. I also have Sony ECM55s, which have a different frequency range and, consequently, pick up sounds differently. As a holdover from my field work in science, I have a couple of highly directional Sennheiser mics, which I bought when I was doing graduate work in Africa 20 years ago, because sometimes the only way to get a good recording in certain settings is with a directional mic. The current model closest to what I have would be the [Sennheiser] MKH 416-P48U3.”
Choosing where to record is part of the fun of nature recording. However, once you begin listening through mics and headphones, you immediately become aware of the presence of unwanted noise in the environment, and finding ways to avoid intrusive sounds is one of a recordist's biggest challenges.
FIG. 13: Ruth Happel is using an MKH 30 and MKH 40 set up on a tripod to record a chimpanzee at Jane Goodall''s research site, Gombe National Reserve, Tanzania.
“In terms of when and where to record,” says Happel, “I have found that in just about anywhere in the United States, it's best to record on early Sunday morning to get the quietest ambiences. If you're interested in species-specific recordings or in ambiences other than a dawn chorus, it might be necessary to invest in a low-frequency filter, which often is built in to mic preamps.” A low-frequency filter is useful in removing the sounds of distant vehicles, for example.
“For foreign trips, it pays to do your research well in advance,” Happel adds. “In all the places I've traveled, there are times of year that are vastly more rewarding for sound recording than others, depending on the activity of birds, frogs, and other wildlife. It is best to consult with field guides, which provide data on vocalizations, including the time of year when animals vocalize, and use any local scientific resources — people, libraries, museums, or universities — to determine the ecology of the destination.”
“In selecting sites for ambient recording, I find topography to be a big challenge in terms of ascertaining the acoustic characteristics of a habitat and negotiating accessibility,” says Quin. For this reason, it's wise to make an equipment list of everything you'll need and run a dress rehearsal before you leave; for example, you might set up your gear in your house or back yard and make a test recording. This will help ensure that you've thought of everything. If you did forget something, add it to your checklist. Bringing backup supplies — extra batteries, blank media, cables — is a good idea, but how much you can realistically pack depends on how much you can adequately carry while getting to and from your destination.
When you're done with your dress rehearsal, make sure to repack everything in your setup. Then, before you leave, consult your checklist again.
NOTES FROM AFIELD
Once your gear is packed, it's time to get out there and record. But like anything else, getting a good recording of natural sounds is about being in the right place at the right time.
“First, you have to put the mic in the right place,” says Trubitt. “Be as fussy as you would in a studio, because the same issues apply in field recording. That's why I like to work with a boom: it encourages experimentation with mic placement. The nice thing about a boom is that you can set the height and then rest it on something if you're doing very long recordings and you don't want to force yourself to be still. Having a tripod or some other thing you can clamp or bolt the mic to and walk away is helpful. Otherwise, you have to be very quiet if you're near the mic.”
One unexpected source of noise for the uninitiated is clothing. Synthetic fabrics, such as nylon, tend to be noisy and should be avoided when recording. When choosing your clothing, grab the material and rub it in your hand; you'll hear right away how noisy it is.
“Another type of noise,” says Trubitt, “is infrasonic handling noise, which happens when a mic is moved quickly. You can sometimes get it when using a shockmount. The result is a powerful low-frequency shudder. You can partially combat handling noise and wind noise with a low-cut filter, assuming you have one available. However, you do so at the expense of low frequencies in the recording. A better solution is to use a windscreen with an integrated suspension mount.”
“You train yourself to be quiet” Happel says. “Because you're listening through headphones, you get used to hearing subtle sounds and you learn to be very quiet. If wind is a problem, I'll unclip the mics and put them somewhere, sometimes deep inside a shrub, well into the vegetation to protect them. It's amazing how much that cuts down on the wind. You can record in a windy ocean setting this way, and it'll completely eliminate the noise problems. And especially if I'm recording an ambience, I'll unclip them and set them down so I don't interrupt the recording with my movement. I listen interactively with the headphones in order to figure out where to place the mics.”
“You must use care in what and when you eat,” warns Knapp. “A rumbling stomach records very well. With some of the more sensitive microphones, I can easily record myself breathing, so I have to practice breathing control. I try to breath quietly and smoothly and position myself outside of the most sensitive part of the mic's pickup pattern. And if you shift the weight on your feet, the crunch of the soil, gravel, or grass will be picked up. But you need to be near to the mic to aim it, because you never know where something may call.”
I asked Krause about the lumps of glue on the switches of his portable DAT recorder. “I hot glue them. When the recorder is in the pack or in my pocket, the switches often get jostled. And I wouldn't necessarily notice that they've been changed, because I can't see too well, even with glasses. So I just glue them into position and forget it. If I need to, I can pull the dried glue off quickly.”
There are ways to protect your equipment from environmental damage. “If you are going to be recording in humid environments, like the rain forest,” says Happel, “you should store your equipment in airtight containers with some sort of desiccant. Otherwise, the mics, and even your recorder, might stop working.”
Quin agrees. “Humidity is always a concern. I carry homemade desiccant sacks and freezer bags when I travel. Extreme cold is also a major challenge. Keeping batteries warm, keeping gear working, and preventing moisture from condensating when transitioning from — 60 degrees Fahrenheit outside to +70 inside can be tricky.”
“I record frogs almost entirely at night, holding a parabolic dish the size of a very large salad bowl, in the darkness,” Knapp says. “I do not turn on a light because all of the insects will home in on me and make unwanted thumps hitting the dish. Standing still and making no sound while being bitten is an art form, but it's part of recording outdoors. I never use DEET-based repellents, because they dissolve equipment. I do use citronella-based repellents, and I also wear loose clothing to keep the worst problems down.”
WATER IN YOUR EARS
Human ears are meant to hear in air. When our ears are physically underwater, we get an impedance mismatch because of the air boundary between the liquid and our hearing apparatus. With the right kind of listening technology, you can experience the sounds your unaided ears cannot hear.
Many sound recordists prefer to record monophonically underwater. Part of the reason is that, to get a usable stereo recording underwater, the distance required between microphones is much larger than what we're accustomed to in air. That is because sound travels faster underwater (approximately 4,987.0 feet per second at 21 degrees centigrade) than in air (approximately 1,128.6 feet per second at sea level in 50 percent humidity).
During a trip to Antarctica, Quin recorded Weddell seals underwater, in stereo. The results are remarkable not only for their sound quality — the recording doesn't have the peaky, band-limited sound that is often a characteristic of hydrophone recordings — but also for the clarity in the stereo image. “I used two International Transducer Corporation ITC-6050C hydrophones,” says Quin, “spaced about 200 feet apart and lowered to a depth of about 50 feet. The positioning was important. I chose a stretch of sea ice that ran parallel to tidal cracks, where seals would come up to breath. It is along these cracks that males vigorously defend their territory during mating.” The omnidirectional hydrophones he used have a built-in preamp and a frequency range of 20 Hz to 75 kHz.
A wide variety of hydrophones are available, with prices ranging from under $100 to well into the thousands. Some recordists experiment with underwater recording by placing a microphone (preferably an expendable one) in an unlubricated latex condom and sealing the end.
“You can also waterproof a microphone by dipping it in Plasti Dip,” says location-recordist Mark Griswold. “It's an epoxy used to rubberize handles on metal tools. The coating is waterproof and flexible enough to transmit sound vibrations, but difficult to remove. The main disadvantage of this technique is the inefficient acoustic coupling of the mic element to the water.”
FIG. 14: This experimental hydrophone created by Rudy Trubitt and Bruce Koball places a piezo between two pieces of Delrin. Silicone is used as a sealant.
A DIY hydrophone can be made using the common piezo element (see Fig. 14). However, the recording quality is often colored by the narrow frequency range of piezos and impedance matching problems. Recordists I spoke with recommend that anyone interested in recording underwater should purchase an inexpensive hydrophone rather than build one (see the sidebar “Hydrophone Sources” at www.emusician.com).
Krause offers some advice when using hydrophones. “Sometimes when you drop a hydrophone into water, it gets little air bubbles around it, which changes the impedance so that it doesn't transmit the sound very well. To get rid of the bubbles, put a little grease on it, like some olive oil.”
HY AND DRY
Surprisingly, some hydrophones work well for terrestrial recording, especially ones that can pick up infrasound or ultrasound. The singing tree, in fact, was captured with a B&K Type 8103 hydrophone, which has a frequency range of 0.1 Hz to 20 kHz (-1.5 dB/+0.5 dB), that also extends up to 100 kHz (-3.5 dB). Of course, you will need a device that can record the extremely low or high frequencies you are after.
Holding another mic in his hand, Krause explains, “The frequency range of this hydrophone, made by Offshore Acoustics, goes down to 3 Hz. Some of the digital Sony recorders, particularly the D10, go down to 3 Hz, into the infrasound and DC range. I used this particular hydrophone to record the sand dunes and to record elephant sounds, because elephant vocalizations are around 14 Hz. Giraffes, hippos, and elephants transmit sound through the air at very low frequencies, which carry over great distances. In fact, hippos vocalize both underwater and in the air.”
A YEAR TO RECORD ONE HOUR
“Wildlife recordings are hard to ‘make,’ to ‘get,’ or to ‘take,’” says Quin. “A good recording of the ‘voice of the wood’ is as much a revelation as it is an acquisition. The disposition of landscape, its features, surfaces and textures, the density of forest, relative humidity and air temperature all mold sound into a distinctive experience.”
However, the first time you actively listen outdoors through microphones and headphones, you may be startled to hear how much man-made sounds compete with the natural ones in the soundscape. “A fraction of what gets recorded will actually be used, in most cases,” says Trubitt. “It depends on the nature of the project. And often you won't know which fraction you're going to use while you're recording. You might use a minute out of 20. Then, two years later, you might need some distant stream ambience, and you might use seconds from the same recording. If you've been out for hours and gotten a few usable minutes, you've done well.”
“When I started, in 1968, it used to take me 14 or 15 hours to get an hour of material,” Krause explains. “Now it takes me 2,000 hours to get that same material. A year to get an hour of usable stuff.”
But even if you're successful in avoiding man-made sounds and have focused on the soundscape you want to record, you may find interference from natural sounds you weren't aware of. “Mics don't discriminate like our ears do,” Krause explains. “Even when you go outside, and your ear tells you you're in a relatively quite place, the mics will pick up ambient sound or noise you are not conscious of. They'll pick up the wind through the leaves and the boughs of trees, or a stream that's a quarter- or half-mile away even though it's a tiny stream; they'll pick up all kinds of stuff that you're desensitized to. Even when you put on your headphones, you don't really hear it until you get back to the quiet of the studio and then all you hear is hiss in the background or traffic from a distant road. And you try and figure out where it came from.”
CREATING THE ILLUSION
The process of recording is just the beginning. The presentation and framing of the audio material, so that it stands on its own, is equally — if not more — important. This is a subject that has been regularly ignored over the years, especially by companies that merely want to cash in with an “environmental” release.
Krause laments about the low quality of many soundscape recordings. “A lot of them just don't sound very good. The stereo imaging and the depth and dimension are not very good. There's no indication that the recordist knows anything about the habitat they recorded in. Often there's no information on the CD about what creatures you're listening to. We need to know about a place beyond the fact that it's an ‘alpine wood.’ In Yellowstone National Park alone, there are hundreds of different habitats. What's there and what are we listening to? This is really important information that people need to pay attention to.”
When he returns to the studio, Krause begins by determining which parts of the recordings can be kept. Then, he crossfades between the good parts, being careful to match the time of the day and the particular characteristics of the biophony.
Which moments Happel uses and how she uses them depends on the artistic statement she's making. “Usually, I end up with bits and pieces and then ask myself, how can I make a meaningful and aesthetically pleasing whole? People's ears are more sophisticated than we give them credit for. They can tell if there's something wrong with a recording. There is an ethics as well as an aesthetics, especially if the goal is to preserve habitat. I try to capture a moment in time, something that's genuine. If you don't, you have to say that.
“If you want a recording to sound realistic, you have to do some combining,” Happel adds. “That's the art in doing this. You need to be creative with the recordings and balance the result so it doesn't sound flat. I want to make people feel like they're in the environment. When I work, the biologist in me tries to be as accurate as possible. I'll sometimes record a single species, then I'll add that to a forest ambience that I've recorded at the same time of day. I'm very aware of what habitats sound like: my background is as a scientist, and I spent ten years recording before trying to do anything musical with it.
“If I'm doing an album,” she continues, “I might layer four or five tracks together: maybe two different stream sounds. It's a fine juggling act, because if you get too contrived, you begin to lose the essence of the environment. The best thing is to find a magic moment in nature and add very little.”
Krause concurs. “The art form is in matching those scenes, and it has to be seamless. There are recordists out there that claim they're purists. My answer to them is that, if you choose a microphone system, you've done some editing; if you choose a recorder, you've done some editing; if you choose the time of day, the location, and where you point your mic, you've made editing decisions. And then you've only got 74 minutes on a CD. Which 74 are you going to choose? Once you've done all that editing, where's the pure?”
Krause often takes his listeners on a journey through a variety of habitats. On his release Whales, Wolves and Eagles of Glacier Bay, the listener travels from the seaside to a meadow, underwater, then back again to dry land to hear the amazing sound of a calving glacier. The slow crossfading between terrestrial water sounds to the underwater world is just one of many remarkable moments on the CD.
“When you're transforming this material to a CD, you're transforming it from one medium to another,” Krause says. “From the natural world into — usually — an architectural interior space. And you better make sure it's listenable. That's where the ‘art’ of the process comes in. That's why so many recordings aren't very good, because people haven't done due diligence to consider how their work is being perceived. You may, as the recordist, be able to imagine the habitat that you've recorded in. When you play your sounds back in the studio, they evoke an image in your mind, but the listener has no such capability, because he or she wasn't there when the recording was made. If what you've created doesn't evoke a visual or visceral sense of that space, then the result is failed ‘art.’”
Krause auditions his projects for a third party for feedback. “I test my recordings on different folks all the time — typically my wife — to see if she gets it.” Does he occasionally get a thumbs down? “Often. More often than I'd like to admit here. That's why I spend so much time in this studio and wear out so much equipment.”
Nature recordists often have to take corrective measures with their source material when they return to the studio. “I usually spend time removing unwanted sounds from otherwise good field recordings,” says Trubitt. “Commonly, I have to diminish rumble, and I use the Waves Renaissance EQ plug-in. A steep highpass filter between 80 and 160 Hz usually does the trick. If my mic preamp turns out to be too noisy on quiet sounds, I use a gradual lowpass filter to remove the hiss. But I'm careful to keep the high-frequency detail intact.”
Krause prefers to do his corrective work in the analog domain, using an Orban parametric EQ. “I use it mostly to remove artifacts, such as low-velocity wind. There's often a low-frequency component to the recorded material in jungles because of far-away streams and stuff like that. Low frequencies carry a much longer distance through the jungle and it's just too distracting to keep it within the context of the recorded product.” One process that Krause does digitally is normalizing recordings to bring up the levels after editing and before he creates the master disc.
For Quin, “editing decisions are made on the basis of what I am trying to create: music, field recording, data for research, radio program, film, or sound design for a museum project. I find that I can revisit the same source recordings again and again and still hear something new, depending on what I am listening for and how I'm trying to ‘translate’ it for the appropriate situation.”
“One of the reasons that I record is that it teaches me critically how to listen,” says Krause. “There are places within the jewel national parks where you can go to hear natural sound unimpeded. As a matter of fact, the National Park Service is the only federal agency and the only group in the country that has designated natural soundscape as a resource. Because they're a federal agency, it means soundscapes must be protected like any other resource. I have found that the natural soundscapes, particularly in North America, are disappearing very quickly. Fully 30 percent of my library, from 35 years of recording, comes from now-extinct habitats — habitats we can't record anymore, because there are no creature voices or they have been so seriously altered that the voice is distressing and sad to listen to.”
Still, getting into the wild natural with your recording gear offers a number of important lessons. “The first thing that you notice when you listen through headphones and a microphone is how much noise there is in our environment, and how it masks much that we want to hear,” Krause explains. “Second, it teaches you how far you have to go to actually get into a place where you can hear natural sound. Third, it changes how you perceive the world, because you don't get information in quick four-frame cuts. The natural story is told gently and subtlely over an extended period of time, because the expression of sound takes a very long time to establish. Often a bird call can take from 45 seconds to many minutes to express. Humpback whale songs can last a half-hour. So you have to sit there and listen while you abide in silence.”
“You don't have to have a digital tape recorder” is Happel's advice to anyone thinking of adventuring outside to record. “Whatever equipment you have, go out and try it: you might be pleasantly surprised with the results.”
Gino Robairis an associate editor atEM.Special thanks to Walter Knapp, Douglas Quin, Ruth Happel, Rudy Trubitt, Jim Cummings, Ben Chadabe, Mark Griswold, Marcos R. Fernandes, and Bernie Krause for their assistance.
The Book of Music and Nature, edited by David Rothenberg and Marta Ulvaeus (Wesleyan, 2001). This excellent anthology offers essays on nature, sound, and the nature of sound by John Cage, David Dunn, Brian Eno, Bernie Krause, Pauline Oliveros, Rainer Maria Rilke, R. Murray Schafer, and many others.
The Microphone Book, by Jon Eargle (Focal Press, 2001). A fine book about microphone technology that includes chapters on recording in stereo. Eargle goes into great detail about the physics behind the various kinds of transducers.
The New Stereo Soundbook, 2nd ed., by Ron Streicher and F. Alton Everest (Audio Engineering Associates, 1998). A straightforward and easy-to-read introduction to stereo recording. The authors do a fine job of explaining how our ears and brains hear and interpret audio information. A wide range of stereo and surround-sound recording techniques are explained and analyzed.
The Tuning of the World, by R. Murray Schafer (Knopf, 1977). A landmark text about acoustic ecology that has inspired many of the recordists mentioned in this article.
Why Do Whales and Children Sing, by David Dunn (Earth Ear, 1999). Dunn's thought-provoking book and CD cover a wide variety of natural phenomena. His audio examples not only demonstrate a particular phenomenon, but his insightful comments can be used as a catalyst for further discussion. The CD alone is worth every penny.
Wild Soundscapes, by Bernie Krause (Wilderness Press, 2002). A field guide designed to introduce nature enthusiasts to the sounds of the wild natural and the joys of recording them. The accompanying CD includes a number of outstanding audio examples, such as singing ants.
RELATED EM ARTICLES Audio-Technica AT835ST review 9/01 “Making Music with Nature: Bernie Krause Samples Life” 5/89 “Playing the Field“ 11/97 Soundman OKM II K review 1/02 “Wild Things” 3/98
Popular Mics for the Field
This list was generated by an informal survey of the mic preferences of a number of nature recordists. It's by no means an exhaustive list, and some of the models may only be available secondhand.
AKG C 1000 cardioid Audio-Technica Model 822 stereo
Model 825 stereo Crown SASS-P quasi-binaural Oktava MK012 cardioid Røde NT4 stereo Schoeps CMC-5/MK-41 and MK-6 Sennheiser ME62 omni
ME66 short shotgun
ME67 long shotgun
MKH-60 short shotgun
MKH-70 long shotgun
MKH-800 variable pattern Shure 183 lavalier
VP88 stereo Sony ECM-55B lavalier
ECM-959 stereo Soundman OKM II K binaural Telinga Pro 5 parabolic
Rudy Trubitt (www.trubitt.com)
Wild Sanctuary (www.wildsanctuary.com)
Yahoo groups (http://groups.yahoo.com):
Books and CDs
Earth Ear (www.earthear.com)
Fourwinds Trading Company (www.fourwinds-trading.com)
The New Stereo Soundbook (www.stereosoundbook.com)
Microphones and Recording Equipment
Cassette House (www.tape.com)
Core Sound (www.core-sound.com)
Microphone Madness (www.microphonemadness.com)
Oade Brothers Audio (www.oade.com)
Sonic Studios (www.sonicstudios.com)