Cajon Asymmetric Panel Design for Acoustic Projection
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Solution Overview
Problem
Existing cajon drums suffer from poor acoustical projection and phase cancellation issues due to identical thickness layers on all sides, leading to inadequate sound intensity and resonance.
Innovation Solution
The cajon design incorporates a striking surface on one side with rigid panels for the top, bottom, and remaining sides, along with a vent hole, and an underlying skeleton to enhance resonance, using thin layers of maple or other materials, and adding mass or damping materials to modify fundamental frequencies and tones, while incorporating a receptacle with small metal items for a snare effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If identical thickness layers are used on all six sides of the cajon, then the construction is simple and symmetric, but poor acoustical projection and phase cancellation occur
Solution Approach 1:
The patent applies asymmetry by using different thicknesses for different sides of the cajon. Specifically, the striking surface (tapa) is made thinner (1/8" to 1/4") to allow better vibration and sound projection, while the back and other sides use thicker material (3/8" to 1/2") for structural stability. This asymmetric construction prevents phase cancellation and improves acoustical projection while maintaining manufacturing feasibility.
Solution Approach 2:
The patent implements local quality by varying the thickness and material properties of different cajon sides according to their specific functional requirements. The striking surface uses thinner, more resonant material optimized for sound production, while the back and side panels use thicker material optimized for structural support. This localized optimization resolves the contradiction between construction simplicity and acoustical quality.
2Reliability
If thin sheets of plywood are used for the striking surface, then the sound projection is improved, but the structural strength is reduced
Solution Approach 1:
The patent uses asymmetric thickness distribution where the striking surface (tapa) is deliberately made thinner (1/8" to 1/4") than the other sides (3/8" to 1/2"). This asymmetry allows the thin striking surface to vibrate freely for improved sound projection while the thicker back and side panels provide the necessary structural strength to prevent collapse.
Solution Approach 2:
The cajon is segmented into different functional zones with different thickness requirements. The striking surface is separated as a distinct thin element optimized for vibration, while the back and side panels are separated as thicker structural elements. This segmentation allows each part to be optimized independently for its specific function, resolving the strength-thinness contradiction.
3Adaptability or versatility
If the top edges are left unattached to allow slapping, then additional percussive sounds are created, but acoustical phase cancellation increases
Solution Approach 1:
The patent applies local quality by making the striking surface (tapa) thinner and more flexible specifically at the areas where percussive action occurs, while maintaining thicker, more rigid back and side panels. This localized differentiation allows the thin striking surface to be slapped for additional percussive sounds while the thicker structural panels prevent phase cancellation and maintain acoustical intensity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly improves sound projection and resonance, allowing for greater intensity and a wider range of tones, including snare effects, by preventing phase cancellation and optimizing internal dimensions for specific musical styles.
Implementation Method 1
prevent loss of volume or acoustical intensity from acoustical phase cancellation of the cajon through the top, bottom, and the remaining sides
Implementation Method 2
percussion sounds are projected from the front panel singly with greater intensity and resonance
Implementation Method 3
a skeleton underlying and supporting selected portions of the striking surface
Implementation Method 4
a mass affixed to a portion of the striking surface to increase the effective mass of the striking surface and to reduce a fundamental frequency of the striking surface
Implementation Method 5
a plurality of small metal items loosely contained within the receptacle so as to provide a snare effect when the striking surface is struck
Data Source
AI summary
Cajones or cajon drums include a variety of improvements over existing cajones. Improvements include improved rigidity of sides other than a side containing a striking surface to prevent loss of volume, a vent hole located on a same side as the striking surface, the use of layers of maple to provide the striking surface, the use of added masses on the striking surface to modify the fundamental frequency of the striking surface, the use of a receptacle containing small metal (copper or silver) items to provide a snare effect, internal dimensions of the cajon chosen to match resonant frequencies of a selected style of music, and the use of damping materials in the cajones to modify the tone.