Cave acoustics can help sculpt more realistic sounds in digital space

Enlarge / Slim pickings: A search for “cave” in Altiverb sampling software shows Howe’s Cavern in NY and two locations in Malta, in addition to several human-made structures. (credit: Yuri Lysoivanov)

Sound is very much an ephemeral phenomenon. So when acoustician Yuri Lysoivanov wanted to capture the unique acoustics of natural caves, he lugged all his recording equipment to Mammoth Cave in Kentucky to analyze the reverberations and resonances. He described this experience at a meeting of the Acoustical Society of America in Victoria, Canada, earlier this month.

Reverberation is a critical design element, especially for performance spaces. It's not the same as an echo, which is what happens when a sound repeats. Reverb is what happens indoors when sound can't travel sufficient distance to produce those echoing delays. Instead, you get a continuous ring that gradually "decays" (fades).

American audio engineer Bill Putnam was the first person to use "artificial reverb" for commercial recording in the late 1940s with the Harmonicats' "Peg o' My Heart"—achieved by placing a microphone and loudspeaker in the recording studio's bathroom. (Bathroom and subway tiles have excellent reverberation, which is why buskers have their favorite spots in New York City's subway stations.) Today, one of the most popular digital techniques is called convolution reverb, which uses recordings of the acoustics of real spaces to produce highly realistic simulations of those spaces.