Course:PHYS341/2018/project/cajon
Cajón
The Cajón, also known as a "box drum", is a box-shaped percussion instrument originally from Peru. Despite the simplicity of its appearance, the cajón is a versatile percussion instrument that can achieve a vast variety of tones.
History
The cajón is the descendent of box drums found in parts of Africa and the Antilles while another popular theory asserts that the cajón was invented by African slaves in coastal Peru to escape the attention of Spanish authorities who prohibited music-making amongst the Black slaves[1]. The wooden crate or box would be seen as a stool or seat instead of a musical instrument. Since the early 1980s, the cajón has been used in contemporary flamenco[2]. It is now a central feature in the rhythm section of most flamenco groups[2].
Physical Structure and Construction
In its simplest form, the cajón is a rectangular wooden box with a hole on one of the sides for resonance. Typically, the frame is created with thicker pieces of hardwood (such as beech, birch, oak, and mahogany) while the playing surface, or “tapa”, is made with a lighter and thinner piece of plywood. The cajón used in this project is made of wood that is quarter and plain sawn. Tapas may also be created with plastic or other synthetic materials. Cajón manufacturers often place four small feet on the cajón's bottom side, thereby adding distance between the drum and the ground for increased resonance. The resonance hole is located on the back of the drum (directly opposite of the tapa). If the cajón has two tapas (i.e. the front and the back side), then the resonance hole is located on the side of the drum.
Nowadays, prior to attaching the tapa to the frame of the cajón, guitar strings or other materials are added to the back of the tapa to create a snare effect. Modern cajóns differ in snare placement and even in tones as snares in cajóns are made to be adjustable.
Geometric Measurements
| Characteristics | Standard Cajón | Mini Cajón |
|---|---|---|
| Height (from the ground up) | 43 cm | 37.7 cm |
| Tapa Height | 45.3 cm | 36.7 cm |
| Tapa Width | 34.5 cm | 25.9 cm |
| Frame Width | 30.3 cm | 26.7 cm |
| Sound Hole Diameter | 11 cm | 10 cm |
| Wood Thickness | 1.5 cm | 0.5 cm |
Fig. 1. A standard cajón.
Fig. 2. Snares inside the Standard Cajón (the snare side).
Fig. 3. A miniature cajón.
Fig. 4. Snares inside the Mini Cajón.
Fig. 5. A diagram of the Standard Cajón.
Playing Technique
The cajón is played by the percussionist siting on the instrument, and percussionists will use their palms or fingertips to hit the face of the instrument. Depending on the style of music or tone that the percussionist wants to achieve, plastic and metal brushes can be used.
Posture
Often percussionists will tilt the cajón, playing the tapa tilted slightly upwards. This technique ensures that acoustics do not get lost in the ground. The percussionist will lean forward slightly and use both hands to hit the drum. Since the percussionist is sitting on top of the cajón, their body will dampen some of the sound.
Hand Techniques
The cajón is a versatile instrument, allowing for a vast variety of tones. The three basic playing techniques are demonstrated in the tutorial video in this article. These three basic techniques produces three separate tones, but other tones can be achieved through the percussionist’s artistic agency.
Acoustics
The cajón resembles a neckless Helmholtz resonator; the air within the cavity of the cajón acts as a spring[3]. Upon hitting the tapa, the air within the cajón is compressed, and a jet of air leaves the cajón via the resonance hole. As with all Helmholtz resonators, the air at the resonance hole acts as a mass that is displaced, shifting in and out of the resonance hole.
The frequency of the drum vibration is dependent on the air mass volume within the cajón and the size of the resonance hole. The greater the hole diameter, the greater the sound pressure level.
The three basic techniques produce respectively, a bass tone, low tone and a high tone. For the purposes of our project, the high tone will not be evaluated.
Note: the sound data collection occurred in various rooms that contained a different amount of sound-absorbing objects (eg: sofas, carpets, etc).
Differences between the Standard and Mini Cajón which may lead to differences in sound measurement are:
- size of cajón
- size of resonance hole
- quality of wood
- placement of snares (Fig. 2 and 4)
- location of resonance holes
Frequency Spectra
In comparing the Standard Cajón's bass and low tones on the Traditional and Snare tapas (Fig. 8 and 9), the bass tones' frequencies tend to be located on the lower end of the frequency while the low tones tend to be more evenly distributed across the spectra. The bass and low tones in the Mini Cajón (Fig. 10) act similarly to the bass and low tones in the Standard Cajón. For all frequency spectra, note that above 400 Hz, the low tone rises above the bass tone, explaining why listeners would perceive the low tone to be higher than the bass tone.
Time Development
In comparing digitized sound recordings of the Standard Cajón's bass and low tones on the Traditional and Snare tapas (Fig. 11-14) the waveforms display a typical attack-sustain-decay of percussion instruments (short attack with short/long decay). There is very little, if any, sustain because the Cajón is hit with a slap. In general, the bass tones decay quicker than the low tones. On the Snare tapa, bass and low tones take longer to decay due to the addition of the snares. It should be noted that without the percussionist sitting on the instrument (Fig.15) the decay takes much longer than if the percussionist were to sit on it, indicating effects of damping by the body. Without the percussionist sitting, the waveform resembles that of the guitar string acting as a snare for the drum.
Fig. 11. Waveform of the Standard Cajon's Snare tapa's Bass tone.
Fig. 12. Waveform of the Standard Cajon's Snare tapa's Low tone.
Fig. 13. Waveform of the Standard Cajon's Traditional tapa's Bass tone.
Fig. 14. Waveform of the Standard Cajon's Traditional tapa's Low tone.
Fig. 15. Recording of the Standard Cajon's Traditional tapa's Bass tone without percussionist sitting on it.
See Also
References
- ↑ Feldman, Heidi Carolyn (2006). Black Rhythms of Peru. Middletown, CT: Wesleyan University Press, p. 21-22.
- ↑ 2.0 2.1 Chuse, Loren (2003). The Cantaoras: Music, Gender, and Identity in Flamenco Song. New York, NY: Routledge, p. 50.
- ↑ Kičák, Peter. "Frequency and Dynamics Analysis of Bass tone of Cajon Box Tone." ACOUSTICS High Tatras 2009, Slovakia, 34th International Acoustical Conference - EAA Symposium, edited by Martin Čulík, n.p., 2009.