Recording a Biophony
May 07, 2007

The Zoom H4 has proven to be a convenient and dependable tool for capturing ambient soundscapes and sound effects outside of a studio environment. My sound library has grown immensely since I started using it last fall, and it has become one of my main tools for capturing sounds out in the world. Even though the recordings can be a bit noisy (the manufacturer states that the preamps have a noise floor of 60dB), the built-in electrets are fairly impressive sounding. The X-Y coincident pair configuration is particularly desirable, capturing a wide and natural sounding stereo image without the setup time typically associated with stereo miking. The H4 is by no means a perfect device, but what matters more is developing good recording techniques and effective workarounds to all the problems that plague field recording. Even the best recorders and microphones out there are capable of capturing poor material if used incorrectly or by someone who is not properly prepared.

As soon as Spring hit, here in New England, I was eager to get out into the warm air and capture some natural habitat sounds. Specifically, I wanted to capture a complete soundscape occurring within some natural terrain; a symphony of creatures. Bernie Krause, a well known nature sound recordist calls this a "biophony". In order to do this, I had to locate a sonically lively biome, research it and record it properly.

Biome: A large, naturally occurring community of flora and fauna occupying a major habitat, such as a forest, grassland, or tundra; a region or biotic community, characterized by particular forms of life that occupy the region. [Krause 151]

At the right time of year, it is not too hard to find a chorus of crickets or tree frogs. As you will see below I never pass up the opportunity to record a habitat as simple as this. However, after reading Bernie Krause's book, Wild Soundscapes, I was hoping to record a dense mixture of birds and animals. This turned out to be more challenging than I thought it would be.

Noise Pollution

I believe that I can speak for everyone, that we prefer the sounds of nature vs. the sound of traffic. The trouble is, if you want to listen to insects and running water, you are forced to listen to vehicles, ventilation systems, jackhammers, chainsaws and sirens. For the most part, these man-made sounds are such a familiar part of our lives that we do not notice them. Below is an example of a sound that one might enjoy during the day, one of the most peaceful sounding spots I could find on Smith College campus. This is also an example of the way machinery plagues field recordings.

nature on campus

Some insensible part of my mind dreamed of walking into the woods and recording hours of singing birds, wind whistling through reeds, howling wolves, screaming bobcats, and maybe even a bear scratching his back on a tree. However, after hiking a couple of miles into a wildlife preserve, All I could hear was the low roar of road traffic two miles behind me, a sky quite active with airplanes and boats humming around on the lake, one mile in front of me. When I did find any sounds worth recording, most of the time noise pollution killed my chances of getting a good recording.

One way to filter out unwanted sounds is use a shotgun microphone. I picked up a Rode NTG-2 shotgun mic and spent some time learning how to use it in tandem with the H4. I thought that this microphone would be useful for filtering out extraneous noises like road vehicles and aircraft. Since I would often be using the NTG-2 outdoors, I fitted it with a Rycote Softie wind shield. To combat handling noise, I purchased an Avantone SSM shockmount and attached a handle. The NTG-2 can get it's phantom power via a AA battery which lasts for over 400 hours so there is no need to wear down the battery in the H4 by turning on phantom power. I have occasionally experienced some strange whining noises in the H4 with phantom power switched on so I am more than happy not to use it.

Shotgun microphones are highly directional so by aiming them about you can focus in on your subject and, theoretically, block out things that you do not want to include in the recording. I've found the NTG-2 effective at zeroing in on specific details of lively natural habitats. Because they are so directional, shotgun microphones produce a more colored recording than with cardioids and omni's. For example, with a shotgun mic you will capture less diffuse-field sound, such as echo and reverberation, which may be desirable or not.

Another way of dealing with noise pollution is to record very early in the morning, in the evening, or even in the dead of night when humans are least active. Weekends are particularly awash with small planes. You will never be more annoyed by aircraft until you are trying to record a habitat while some weekend pilot circles the sky for an hour, then goes back to the airport for more fuel and does it again.

If you're using directional microphones horizontally it really helps to position yourself in such a way that the worst traffic noise is as off-axis as possible. Shotgun microphones actually do not provide the most rejection directly in the rear of the microphone, at 180 degrees, but instead at 120 and 135 degrees (just over your left and right shoulders, if you are aiming the mic straight in front of you). An example application for the shotgun mic: You are in a city park recording birds in a tree. You are pointing it upwards to reject sounds all around you, and at a slight angle forward, in order to reject the heaviest traffic sounds behind you.

Wind

Wind sounds are a great addition to natural soundscapes. Whether or not you want them in your recording, if you are not armed with a way to prevent gusts from directly hitting the diaphragms, you may not be able to record at all.

I recently came up with a dirt cheap but effective solution to recording with the H4 in windy conditions. First, attach the little tripod that the H4 comes with, then fasten the supplied foam windscreen and place the H4 where you would like to record from (on the ground, for example). Then put a plastic milk crate upside down over the H4 (one of these) and drape a soft, fuzzy beach towel over the crate. This simulates the way a wind zeppelin works; there is a thick blanket of still air around the microphones. With this method, you will hear no wind rumble at all and very little coloration to the sound. When wind speeds reach 50mph or more, just throw another towel on. The crate also doubles as a way to carry all your recording stuff around, the towels are good packing material, and when the wind dies down, you've got something to sit on! Obviously, this only works when recording from a stationary position. Another drawback is that you will have to find a surface that will support the crate. Often times the best recording position is in mid-air. In a situation like this, I use a telescoping speaker stand to support the crate (pictured) and I keep some small clamps with me to keep the crate from blowing off the stand. I've only recently discovered this milk crate technique and have hardly had a chance to take advantage of it, but it is now part of my field recording kit for high wind conditions.

Omnidirectional mics are better in gusty conditions, so, presumptively, if you hooked up a pair of them to the H4, you would have much less of a problem and might be able to simply shield them with your body or place them on the ground. (I'll be testing a pair of Audio Technica AT3032 omni's with the H4 soon and will post my findings).

Most H4 users agree that the supplied foam ball does not help the wind problem a whole lot and want something similar to it but with better protection. One of the problems, as a fellow H4 user recently pointed out to me, is a gap that forms between the shield and body of the device, creating an open path to the diaphragms. Additionally, the ball does not stay on that well and is easy to lose (and perhaps chewed and swallowed by the dog). Once during this project I had to go on a long hunt for it in the woods with my flashlight. I nearly gave up, thinking that I could probably get a clown nose for it. How much easier it would be to find if it were red!

X/Y handheld mics from Audio Technica come with fairly large foam covers, the AT8120 windscreen. By cutting the bottom off of one with scissors, one can fit it snugly over the entire top of the recorder. Of course, this solution does not work as well as my milk crate technique (conceited laugh), but it is a noticeable improvement over the ball, it is portable and not likely to fall off.

Habitat Research

My first mission was to get familiar with the local wildlife and find out where I might get a good recording. I did not expect to get my recording right away and decided that I should just plan on doing some looking around first. I brought my field recording kit with me, captured whatever I could and usually analyzed the recordings closely at home.

I didn't hear too many creatures during my initial visits to the woods, just an occasional bird chirp here and there. I could not hear much of anything that sounded like a complete natural habitat. Sometimes, a chipmunk would see me, send out an alarm call to several neighboring chipmunks and then the entire forest was chittering with agitated animals. This could hardly pass as a biophony!

In the Connecticut River Valley, spring starts with a chorus of nocturnal tree frogs called Spring Peepers, which congregate in damp fields and in low laying vegetation along the edges of water. At the beginning of their mating season they are about the only wildlife that you will hear in many parts of the valley. It's easy enough to find them but since this area is fairly overloaded with road vehicles and air traffic, it was a little difficult to record them in isolation. At 1AM, driving into the back woods of Leverett MA with my windows rolled down, I found a remote pond full of tree frog activity. I parked my car and walked into the pitch black woods and found a spot to record from.

night peepers 1 | night peepers 2

Both of these recordings were made using the H4's internal microphones. "Night Peepers 1" was recorded by placing the H4 on a log, far away from the waters edge where the frogs seemed to be. This sound is representational of how we normally hear peepers; a singular droning chorus in the distance.

If you are close to a large congregation, you will notice that certain areas of the pond go silent for several minutes, swell up into energy and then go silent again as another group of frogs some distance away takes over. People do not usually notice this rhythmic pattern when listening to frogs at a distance. Inside the congregation, one can hear interludes, long rests, different types of vocalizations and, after getting familiar with their language, a sense of when a group is about to swell up again. "Night Peepers 2" was recorded at close proximity to the waters edge, by holding the H4 in mid-air toward the center of the pond. In this recording you can hear a group of frogs at one end of the pond rising from silence to full symphony over a period of about one minute. You can even hear them jumping around on the ground. I did not hear any vehicles that night. Perhaps the frogs and wind were so loud that they overpowered the distant vehicles.

In some areas, Spring Peepers can be heard during daylight. On the following afternoon, I found a nice place to record Spring Peepers: a wooded area near Quabbin Reservoir. In this recording I was able to capture a mixture of frogs and a few birds. I was having quite a lot of trouble because of noise pollution though. I often had to wait for up to 45 minutes for a one minute stretch when vehicles could not be heard. This was a lot more difficult than the previous night, but I was at least getting a slight mixture of animals. At one point, I noticed that the peepers reacted to a thundering jet and went completely silent for about 20 seconds. When they started up again, they sounded hesitant, almost nervous. I wondered how this soundscape would evolve if there there were no human sounds to disturb it. After experiencing this, I happened upon the following passage in Wild Soundcapes. Krause was speaking about the effects of a low-flying jet on a congregation of frogs that he was recording:

When you are listening in certain habitats, many types of frogs and insects vocalize together so that no one individual stands out among the many. This chorusing creates a protective audio performance that keeps predators from locating any single point from which the sound originates and thus isolating any particular creature. The frog voices emanate from so many places at once that they sound as if they are coming from everywhere. When the coherent patterns are upset by the sound of a jet plane or some other loud disturbance within the range of the pond, the special frog choral synchronicity is broken. In an attempt to reestablish the unified rhythm and chorus, individual frogs momentarily stand out. This gives predators, like coyotes or owls, a perfect opportunity to snag a meal. After the jet disappeared, a total of 45 minutes went by before the toads had reestablished their protective chorus.

"Day peepers 2" was recorded with the NTG-2 shotgun. I focused in on one of the frogs, effectively bringing it to the forefront of the symphony. With the shotgun mic, I was able to filter out the cars and wind pretty easily.

day peepers 1 | day peepers 2

I think that these are good recordings but I was still hoping to get a biophony that included a mixture of animals. My search continued..

The Quabbin Reservoir is the largest body of water in Massachusetts and was formed in the early 1900's by damming the Swift River which, over a period of seven years, filled the Swift River Valley with 412 billion gallons of water. Several towns were disincorporated, houses were removed and 81,000 acres of quiet watershed lands was put under state protection. The Quabbin waterfront seemed like it would be a good place to search for a biophony. I knew there were some Common Loons there and I was hoping to get a mixture of loons and waves. During the day, the surface of the water is usually pretty active. The wind often kicks up a bit sunset and then just as the sun sets the water gets very still and quiet. I thought that the waves would be a good ingredient for a biophony as they would help provide a geological setting for loon calls but since the waves happened during the day and the loons called mostly at dusk I would have trouble catching a mixture.

One rainy Sunday, late in the afternoon, I spent hours trying to get this recording. There were many boats on the water, despite the rain, and the loons only called out a long distance away about once every half hour, always when boats were buzzing across the reservoir. A couple of loons flew close by and I followed them as best I could but eventually they disappeared. The wind and rain was making it nearly impossible to set up the H4 (I had not come up with the milk crate solution yet!) I kept the H4 inside a plastic bag most of the time, waiting for the boats to leave, the rain to stop, the wind to subside and the loons to come back...Oh, and yes there were airplanes. Lots of airplanes. In the following recordings, I was able to get a mixture of wave action and a few birds.

wave action 1 | wave action 2

Even though I was having trouble recording a good biophony down at the waters edge, I felt that there was a lot of potential to get a complex recording in this particular area of the reservoir. All the ingredients were there, however sparse and unpredictable. I just didn't know how I could capture all the sounds at once.

One day, as I left the reservoir and had nearly reached my car, I saw swarms of birds flying around over a nearby marsh. Occasionally a bunch of them would land in the trees above me where it was quite easy to get a recording of them with the NTG-2. Since the microphone was aimed straight up, the traffic sounds were not too noticeable. Because of the roads, it was not a good area to record a biophony, but it gave me the idea to start looking to marshes to find a biophony.

I used Google Maps' satellite imagery to locate a large marsh in the Quabbin, far away from roads. I found something that looked like it might be a marsh and set out to reach it on foot. I packed a lunch, and planned to spend an entire day there, in anticipation that this place would be full of birds, frogs and trickling water.

After a long drive followed by a long walk down an old paved road I could see the marsh ahead of me. In order to get to it I had to thrust my way through a lot of low shrubs and picker bushes on the side of the road. I zipped up my gear bags tightly and made my way down to the marsh and when I just cleared the last bush, I felt something crawling on my hand, a tick, which I quickly flicked off. I looked down at my legs and saw about twenty more of them crawling upward, which I brushed off vigorously. I was sure that they were getting inside my clothes, which was especially disturbing since I always get a severe rash when bitten by them. However, I had already trudged my way down to what seemed like a good recording spot so I figured that I might as well make it a worthwhile endeavor.

I was standing on a plateau that overlooked a wide open marsh. In the center of the marsh a large stream roared. It was so fast moving and far away that it did not have much sonic detail to it. I knew that this stream might just sound like white noise in my recording. I could hear some frogs but they were a good distance away. There were lots of birds flying around but they were dispersed over such a large area that I could not hear too many of them. I made a few recordings with the NTG-2 and H4 microphones but it was evident that this recording location was too far away from the action. If I moved any direction from the plateau I was on though, I would be covered in ticks again. I decided that I had better make my way out of there and find a marsh that was not infested with blood sucking parasites. When I got home I was happy to find that only two ticks had attached themselves to me.

I learned something on this little adventure: a larger biome does not mean that it will be any easier to get a good recording. In fact, it may even be more difficult. In previous days I had been able to find little vernal pools teaming with spring peepers. But in the large marsh, the peepers were much farther apart and more difficult to approach. Perhaps what I wanted was a very small marsh, I thought. One that I could easily approach from all sides. This might bring different creatures closer together.

An Emerging Soundscape

The following day was very windy and at sunset I went back to the area where I had heard the loons, hoping that they would return. As I walked towards the water I noticed a patch of marsh grass which I had passed several times before. There were a couple of peepers and Red-Winged Blackbird nearby so I sat down on a large rock with the NTG-2 and aimed it upwards to capture four different vocalizations that it was making. Several minutes later, another blackbird arrived, and soon after that there were at least four of them. Since the sun was setting, the frogs started to pick up and the soundscape started to get lively. More and more Red-Winged blackbirds arrived and they congregated in the patch of marshgrass. They got completely boisterous and I could hear them splashing around in water, wind humming through their feathers as they dived into the grass and even a duck flying overhead. A soundscape was not only emerging in a previously quiet area, but it was slowly transforming as the sky grew dark. By the time moonlight had replaced the sun, the birds went silent and the frogs took over. The window, when it was possible to record the birds and frogs together, eventually closed. Below you can listen to a series of recordings I made with the NTG-2, each one representing what was going on in the grass at fifteen minute intervals.

I decided that I would focus on this area and returned on the following night, just before 7:30PM. I was hoping that the loons would be calling but when I arrived I did not hear them. I was fairly certain that the birds would come back because I could hear a couple of them in a nearby tree. When the time was right, I set up the H4 on a small tripod near a trickling stream and aimed it at the same patch of grass that I had recorded with the NTG-2 the previous night. I thought that this low level water sound would make a good addition to the soundscape. Since the air was windless, I was confident that I could make a recording without microphone rumble, even without the H4's foam windshield. My back was towards the heaviest traffic sounds but there were still quite a few aircraft passing by. I waited for them to leave, put on my headphones, and hit record. About one minute into the recording, which consisted of frogs and blackbirds, I could hear loons on the water. Then I could hear a bullfrog glurping just over my left shoulder. The Redwinged-Blackbirds got a bit more silent, maybe because of the long droning sound that the loons were making, as if they were giving the loons time to speak. Even the peepers died down a bit when the loons started calling "kooo-waah-leeeee". There was a nice symphonic balance going on in this biome and I was able to capture a clean recording of it.

reservoir biophony

...I transferred short recorded samples from my time in Africa to a device that graphically displays them as "voice prints" or "spectrograms". Patterns between the sounds of insects, birds, mammals and amphibians were immediately evident and differentiated almost as distinctly as notes on a symphonic score. This animal symphony, the unique manner in which creatures vocalize in a symbiotic relationship to one another in any given healthy habitat is what I call biophony. [Krause 24]

In the image below, I have rendered a spectrogram of the reservoir biophony. A spectrogram is a visual representation of a recording, displaying time, frequency, and amplitude. Time is on the horizontal axis (15 seconds from left to right), frequency is on the vertical axis (0-6000Hz), and amplitude corresponds to brightness (the brighter the pattern, the louder the sound). I have included some of the bird song mnemonics in the labels, to better explain the pattern.

Among other things, spectrograms are excellent tools to document and study how animals interact with each other, behave at different times of the day and react to man-made disturbances. Sometimes, in order to have an understanding of the pattern you have to study a lot of material. There are things going on in biophonies that most people are just not conscious enough to notice. I will return to this area in the future and study how the soundscape changes over time.

References:

Holman, Tomlinson. Sound for Film and Television, Second Edition. New York: Focal Press, 1997

Krause, Bernie. Wild Soundscapes. Berkeley: Wilderness Press, 2002

Schafer, Murray R. The Soundscape, The Tuning of the World. Rochester: Destiny Books, 1977

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