OLD LYME, CONNECTICUT: Tucked away in the concrete jungle of New York, the Bronx Zoo recently opened the Congo Gorilla Forest Exhibit - a huge 6.5 acre Central African rainforest. Congo's designers strove for realism and authenticity down to the smallest detail, and, in keeping with their rigorous standards, hired Ken Kresge to supply ambient soundtracks. The Bronx Zoo hired Kresge after hearing his work on the Jungle Trails exhibit at the Cincinnati Zoo, which won the American Zoo and Aquarium Association's prestigious Exhibit of the Year award in 1993 and showcased Kresge as a master in this narrowly niched field.

Since budgets for ambient soundtrack work are typically lower than other commercial installations, Kresge sought sound sources closer than Africa. The El Junque rainforest in Puerto Rico served as a fertile hunting ground for a man armed with microphones. "The rainforest is so alive. When you close your eyes, you find that even the vegetation makes a steady stream of dripping, brushing, and wind sounds."

Kresge's field recording outfit consists of two Sennheiser MKH 416 shotgun condenser microphones with Sennheiser zeppelins and shock-mounts and a Tascam DA-P1 portable DAT recorder. About his choice of microphones, Kresge remarked, "whether you're recording classical piano or natural sounds, the whole idea is to get a flat response so that the sound can be reproduced naturally. The 416s are wonderfully transparent and natural sounding. There's just something about those German microphones that capture such a rich quality of sound. In addition to great sound, the 416s are built like tanks and impervious to the hazards in the field."

Kresge has both microphones mounted on a single pole that attaches to a shoulder harness for hands-free mobility. He keeps the microphones seven inches apart (the width of a standard human head) and spread ever so slightly from parallel. "That slight difference really gives the stereo effect a wonderful image", commented Kresge.

The super-cardioid polar pattern of the MKH 416s work to reject 'stray' noises from interfering with his 'target' as do the Sennheiser BP-2 microphone power supplies that Kresge tucks away in his Porta-Brace with the DAT recorder. "The BP-2s have a high-pass filter that I employ to reduce the low frequency content in the field. There's a lot more low frequency noise out there than you would think," noted Kresge.

For those sounds that Kresge could not obtain from the wilds of the Western Hemisphere, he turned to the zoo itself. Among the many creatures recorded in the zoo, one of the more interesting was the mandrill, a large, magnificent baboon. Kresge obtained permission to enter their holding area and set up his MKH 416s. He quickly learned that the mandrills would only vocalize if he ran back and forth in front of their holding area! Kresge placed the MKH 416s between himself and the mandrills, and their highly directional pickup pattern permitted him to record the mandrills without his footfalls.

Would it be enough too simply go into the field, record ambience, and play it at the exhibit? Kresge thinks not. "I'll use an existing ambient recording as a reference, but an undoctored track is dull, lifeless, and unexciting." So Kresge uses a ProTools|24 editing suite to build his tracks from the ground up. "I start by editing each individual sound, trying to isolate it. I remove any hum or background noise with EQ and noise reduction as much as possible." Once all the individual samples are tweaked, he arranges various 10-15 minute loops of insects and frogs. With that loop repeating over the course of the CD, he peppers the more "out-front" sounds such as birds and primates over the duration.

Congo's designers are delighted with the results. The soundtracks accentuate the exhibit's coherence and fidelity to the genuine Congo rainforests without being garish.