The cajón is known for producing a wide range of sounds and timbres from a simple wood box, with guitar strings tucked inside that rattle when the box is struck by the player's hand. A student-led research thesis in Kettering University’s Acoustic Lab is examining how properties of the cajón can be studied to optimize this Latin percussion instrument.

John Pehmoeller with a cajón in the Acoustic Lab.

“The goal is to understand the properties,” said John Pehmoeller, a senior majoring in Mechanical Engineering. “I’m hopeful the research can be used to improve the instrument. If we understand the properties, we could change it structurally to get better sound or make it easier to play.”

Pehmoeller’s project is one of several research thesis projects in the Acoustic Lab that combine aspects of physics, engineering, mathematics, sciences and even the arts.

“We have a multi-disciplinary approach,” said Dr. Dan Ludwigsen, associate professor of Physics at Kettering University. “Typically, this type of research is done in engineering departments. Here at Kettering in the Acoustic Lab, we’re doing it in Engineering Physics and Applied Physics. It’s the junction of Physics, Mechanical Engineering, Electrical Engineering and even subjects like psychology and customer preferences when it comes to designing products that will sound good to consumers.”

Although Pehmoeller’s research is scientific in nature, it also has creative motivations.

“The project results mostly from pure curiosity,” Ludwigsen said. “Why does the cajón work the way it works? Once you answer that question, you start to think, ‘How could it work better?’ You could design a front panel so it’s more comfortable or ergonomic, you could look at how improved balance could make the tones more beautiful. It’s combining science with an appreciation for the aesthetic qualities.”

The many multi-disciplinary opportunities the lab creates are an asset for students conducting research. Kyle Smith, a senior double-majoring in Engineering Physics and Mechanical Engineering, worked with Dr. David Parker, emeritus faculty in the Kettering Department of Physics, to construct a laser interferometer. The project entailed Mechanical Engineering skills as well as two areas of interest in Physics.

“Kyle’s project is a nice combination of the Kettering Physics Department’s expertise in optics along with our interest in vibration,” Ludwigsen said.

Kyle Smith in the Acoustic Lab.

The apparatus uses laser beams and mirrors to illuminate on an object. A camera is used to combine images, and interference patterns are examined to show displacement of an object.

“It’s useful for the visualization of vibrations,” Smith said. “You can see real-time movement in two dimensions and it can provide very precise measurements.”

Two other seniors -- James Shurish (Applied Physics major) and Evan Hulscher (Engineering Physics/Mechanical Engineering double major) -- have worked on a project to modify a Helmholtz resonator. Helmholtz resonators are used to help reduce unwanted sounds.

“The resonator is modified with a flexible membrane bottom which vibrates with the resonance response of the resonator,” Shurish said. Efforts were made using computational software (COMSOL) in order to modify the frequency response function as well as oscillation amplitude of the system. Finally, a study was done in regards to altering the geometry of the membrane in order to couple different material properties together. Theory was used in order to verify results of the computation.”

The capabilities of the Acoustic Lab and the research opportunities it provides are unique for students. The chance to work closely with faculty also enhances student research.

“I don’t know of another university that would let an undergraduate work on a project like this,” Smith said. “It’s a great project to work on, and so many  professors have helped me.”

The students also benefit by not only gaining hands-on experience in applied research, but also learning how to convey and present their findings.

“Students get to do poster presentations and conference talks that result from their research,” Ludwigsen said. “John (Pehmoeller) is working on a manuscript for potential journal publication. What these students pick up is a really specific experience and skillset they can point to when they encounter a challenging problem. They’re better able to take the initiative to solve the problem when they’ve gone through research experience like this.”

The collaborations that develop are also valuable for faculty.

“Through these collaborations, you develop a bigger picture of how the students from different backgrounds we work with every day learn,” Ludwigsen said. “Working with faculty also gives me more examples to use from other disciplines in my own classes. The more we collaborate, the more we learn as scholars and the more we can share with students.”