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Acoustic waveguide technology

The challenge

The challenge Bose engineers faced in the 1970s was as multi-layered as a piece of music. Big speakers were required to produce the wide range of frequencies found in a song, from the intricate notes of a violin to the deep low frequencies of a bass guitar. A rack of components was needed to keep up with the massive speakers. Suddenly, the simple goal of enjoying quality sound was complicated and space consuming.

Music also presented an inspiration with a device called an "acoustic waveguide." This simple device confines the movement of a sound wave so it travels over a desired path. An example is a pipe organ, which uses a small amount of air to fill a cathedral with full, rich sound.

A single breath of air can fill a room with sound

Another example is a flute. By blowing a stream of air across the mouthpiece, a musician can produce enough sound to fill a large room. However, both of these instruments have a serious limitation where loudspeakers are concerned—production of different notes requires waveguides of different lengths. This is created either through fingering, as in the flute, or by selecting another length of pipe, as in the organ.

Dr. Amar Bose and a senior Bose research engineer, Dr. William R. Short, had the foundation for the technology, but their path was still littered with challenging questions. How can you utilize a single acoustic waveguide if it can only reproduce a single note? How can you keep a system compact if, like an organ, you need dozens of pipes to produce a wide range of sound?

It would take 14 years of research to find the answer—acoustic waveguide speaker technology.

Next: The solution »

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