Voices of Earth: A Global Symphony is a 10 -minute video sample of a sound installation first presented in 2004 at the Pozen Center for Interrelated Media in Boston by John Holland and Josh Caswell. The original program was a 24-hour musical simulation of various acoustic phenomena, computer-controlled in real time, from sunset to sunset.
A variety of acoustic phenomena that vibrate outside the normal range of human hearing, such as the continuous rotation of the Earth, high and low atmospheric pressure systems, ocean waves, tidal motions, earthquakes, storm cycles, mountain waves, heartbeat, breathing, stress waves, etc. were converted to musical tones by transposing their frequencies and amplitudes to within the range of human audibility. The quality of each sound was determined according to the medium in which the sound occurs: air, liquid solid, organic substance.
A computer was programmed to organize start and stop times for continuous tones, pulses, and cycles relative to their durations within a period of a single rotation of the earth.
In addition, there are a variety of sampled sounds that are integrated into the music. These range from electronic sounds, environmental noises such as rain, wind, and thunder, to human speech sounds representing more than 25 different languages. Sampled sounds also include various animals, birds, and insects that are representative of diverse regions and environments throughout the world. The computer was used to control the selection of individual sounds, and their respective start times.
Screen images of the various acoustic phenomena accompany the music, including many low-orbit satellite photographs mined from NASA’s Visible Earth collection.