The cajon is a percussion instrument with origins in 16th century Peru. Literally translated “crate,” the cajon was originally a crate that players sat upon and struck to make rhythmic patterns. The modern version is a wooden box, closed except for a hole in the back panel. The front panel is struck with the hands or one of several types of beaters. The front panel is thinner than the others and is often attached with a slightly loose top edge for a snare-like effect. Alternatively, the snare sound is obtained with wires or guitar strings placed against the inside surface of the front panel, and these rattle when the panel is struck. Measurements of acoustic transfer functions with impulse excitation and roving hammer structural measurements explore the acoustic and structural resonances of the cajon with rattling strings removed. Spectra from recordings establish timbral features of the instrument, both with and without the rattling strings. By comparing results from measurements and recordings, the important features of the particular instrument tested in this study are identified, and possible directions for improved the designs are suggested.