The Science Behind ‘Beatboxing’

Acoustical analysis reveals the anatomy behind the fascinating array of sounds people can make.

Using the mouth, lips, tongue and voice to generate sounds that one might never expect to come from the human body is the specialty of the artists known as beatboxers. Now scientists have used scanners to peer into a beatboxer as he performed his craft to reveal the secrets of this mysterious art.

The human voice has long been used to generate percussion effects in many cultures, including North American scat singing, Celtic lilting and diddling, and Chinese kouji performances. In southern Indian classical music, konnakol is the percussive speech of the solkattu rhythmic form. In contemporary pop music, the relatively young vocal art form of beatboxing is an element of hip-hop culture.

Until now, the phonetics of these percussion effects were not examined in detail. For instance, it was unknown to what extent beatboxers produced sounds already used within human language.

To learn more about beatboxing, scientists analyzed a 27-year-old male performing in real-time using MRI. This gave researchers “an opportunity to study the sounds people produce in much greater detail than has previously been possible,” said Shrikanth Narayanan, a speech and audio engineer at the University of Southern California in Los Angeles. “The overarching goals of our work drive at larger questions related to the nature of sound production and mental processing in human communication, and a study like this is a small part of the larger puzzle.”

The investigators made 40 recordings each lasting 20-40 seconds long as the beatboxer produced all the effects in his repertoire, as individual sounds, composite beats, rapped lyrics, sung lyrics and freestyle combinations of these elements. He categorized 17 distinct percussion sounds into five instrumental classes — kick drums, rim shots, snare drums, hi-hats, and cymbals. The artist demonstrated his repertoire at several different tempos, ranging from slower at roughly 88 beats per minute, to faster at 104.

"We were astonished by the complex elegance of the vocal movements and the sounds being created in beatboxing, which in itself is an amazing artistic display," Narayanan said. "This incredible vocal instrument and its many capabilities continue to amaze us, from the intricate choreography of the ‘dance of the tongue’ to the complex aerodynamics that work together to create a rich tapestry of sounds that encode not only meaning but also a wide range of emotions."

"It is absolutely amazing that a person can make these sounds — that a person has such control over the timing of various parts of the speech apparatus," said phonetician Donna Erickson at the Showa University of Music and Sophia University, both in Japan, who did not participate in this study. "It is very exciting to see how far technology has come — that we can see these movements in real time. It gives us a much better understanding of how the various parts of our speech anatomy work."

Songbird sings in 3D

The question ‘How do songbirds sing?’ is addressed in a study published in BioMed Central’s open access journal BMC Biology. High-field magnetic resonance imaging and micro-computed tomography have been used to construct stunning high resolution, 3D, images, as well as a data set “morphome” of the zebra finch (Taeniopygia guttata) vocal organ, the syrinx.

Like humans, songbirds learn their vocalizations by imitation. Since their songs are used for finding a mate and retaining territories, birdsong is very important for reproductive success.

The syrinx, located at the point where the trachea splits in two to send air to the lungs, is unique to birds and performs the same function as vocal cords in humans.  Birds can have such a complete control over the syrinx, with sub-millisecond precision, that in some cases they are even able to mimic human speech.

Despite great inroads in uncovering the neural control of birdsong, the anatomy of the complex physical structures that generate sound have been less well understood.

The multinational team has generated interactive 3D PDF models of the syringeal skeleton, soft tissues, cartilaginous pads, and muscles affecting sound production. These models show in detail the delicate balance between strength, and lightness of bones and cartilage required to support and alter the vibrating membranes of the syrinx at superfast speeds.

Dr Coen Elemans, from the University of Southern Denmark, who led this study, explained, “This study provides the basis to analyze the micromechanics, and exact neural and muscular control of the syrinx. For example, we describe a cartilaginous structure which may allow the zebra finch to precisely control its songs by uncoupling sound frequency and volume.” In addition, the researchers found a previously unrecognized Y-shaped structure on the sternum which corresponds to the shape of the syrinx and could help stabilize sound production.