The Physics of a “Just Right” Guitar

A 68-millimeter-thick instrument produces the best-quality sound

Join Our Community of Science Lovers!

Kazutaka Itako, an electrical engineer at the Kanagawa Institute of Technology in Japan, has played the guitar since he was six years old. Satoshi Itako, who has a master's degree in electrical engineering, works as a guitar fabricator. Together the brothers have been investigating the optimal shape for guitars.

Experts have settled many questions relating to the best shape for violins, but far less research has been done on guitars. The Itakos' preliminary work, presented in May at the Acoustics 2012 conference in Hong Kong, looks at one variable: guitar depth. They crafted four nearly identical instruments, ranging from 58 to 98 millimeters deep.

The Itako brothers tested the tonal quality and harmonics of four guitars, while a performer played open strings with two different strumming styles, using both objective and subjective measures. With an oscilloscope, they measured the harmonics, integral multiples of a fundamental tone. (A pure wave has only one frequency, yet it sounds sterile and artificial. The more harmonics, the richer the sound quality.) In addition, nine musically trained listeners evaluated the guitars.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

The 68-mm-thick guitar included the richest combination of harmonics, and six of the nine listeners rated it as having the best tone quality. The Itakos are now moving on to the question of how the size of the sound hole alters the guitar's tone. After that, they plan to determine whether a synthetic material, such as fiberglass, could make instruments that are just as sonorous as wood versions, which are time-consuming and finicky to make. The Itakos' goal is to identify ideal dimensions and materials for a high-quality subprofessional instrument, which would allow more amateur strummers to buy good guitars at affordable prices.

COMMENT ATScientificAmerican.com/oct2012

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American