via The Acoustical Society of America
The use of artificial reverberation in recorded music has been available since the late 1940s and is commonly credited to the ingenuity of Bill Putnam Sr. [1]. Following decades of technological achievement audio engineers are able to access an ever-growing variety of echo chambers, metal plates, springs, and digital emulations of an abundance of environments. A popular method in use today is the convolution reverb, a digital technique that uses controlled recordings of real spaces (called Impulse Responses or IRs) and applies them to every sample of a source sound, achieving an incredibly realistic simulation of that sound in the space.
Curiously, given their unique acoustic qualities, impulse responses of caves are generally underrepresented in the audio engineer’s toolkit. A browse through the responses in Altiverb, a popular high-end convolution reverb (figure 1), shows a small selection of caves relegated to the post-production (i.e. film sound) category ready to use for enterprising sound designers. This selection is far smaller than the availability of concert halls, churches, tombs, rooms and other acoustically critical spaces.
For this paper, we sought to explore nature as architect and to demonstrate how incorporating the characteristics of these distinct structures can make a meaningful contribution to the audio engineer’s creative palate. With the aid of scientists from the National Parks Service, we chose a few locations for analysis within Mammoth Cave – the longest cave system in the world.