FREQUENCY AND DYNAMICS ANALYSIS OF BASS TONE OF CAJON BOX DRUM
Peter Kičák · 2009
The paper deals with the resonance of cuboid enclosed air mass with circular hole and sounding board of cajon box drum. Experimental cajon drum has internal dimensions of 260×280×470 mm, sounding board is made of thin 3-ply plywood and resonance hole has diameter about 120 mm. When playing cajon box drum, the sounding board is striking by hand about midway between center of sounding board and top edge and therefore is excited mainly (0,0) mode of rectangular plate with clamped edges. Frequency of this mode varies around 110 Hz and it is the strongest sound of instrument. Experimental instrument was excited by falling silicone ball to about midway between center and edge of sounding board. The diameter of resonance hole was enlarged for each experiment from 70 to 170 mm by steps of 10 mm. The sound pressure level (SPL) of excited instrument was measured by sound level meter BK2218 using octave filter BK1613, set to 125 Hz. The sound was recorded through the 24bit/96kHz recording system to the computer for frequency analysis. There is an assumption of Helmholz resonance uprising. Objective of this measurement is to prove or disprove this phenomenon in case of cajon box drum.