Reference document for the Mautak Tuning Chart project. Written as a working map of the existing literature — what has been measured on other bamboo species, how it was measured, and what the field-scale equivalent for Mautak should record. Revised as new work is published.
the short answer
Three research groups in the world have published systematic acoustic data on bamboo for musical-instrument purposes. All three work on Chinese or Southeast Asian species. None have studied any South Asian species. None have studied Melocanna baccifera. The sections below set out what each group measured, how they measured it, and what the equivalent field-grade record for Mizoram needs to look like.
study 1 — song et al., the primary model
Song, J. et al. (2023) ‘Scientific mechanism of bamboo acoustic vibration performance from structure-chemical perspective’, Industrial Crops and Products, 200, 116817.
Species: Phyllostachys pubescens (moso). The most commercially important bamboo in China.
This is the most important paper in the set. The data format and the parameter selection are the primary reference for any subsequent acoustic characterisation of bamboo.
acoustic properties by biological age
| Bamboo age | E’/ρ (GPa·cm³/g) | tanδ | ACE (m⁴/kg·s) | E’/G’ ratio |
|---|---|---|---|---|
| 2-year | 16.77 | 0.0168 | 997 | 8.34 |
| 5-year | 18.97 | 0.0148 | 1,284 | 8.64 |
| 8-year | 20.39 | 0.0150 | 1,356 | 9.49 |
What the parameters measure:
E’/ρ — specific dynamic elastic modulus. The stiffness-to-density ratio. A higher value means the material is stiffer per unit mass, which translates to a more efficient conversion of mechanical impact into vibration. Colloquially: how ringy is this bamboo. Song et al. measured it by free-free flexural vibration — support the specimen at its vibration nodes (22.4 per cent from each end), tap it, record the vibration, and derive E’/ρ from the resonant frequency and the specimen’s dimensions and weight.
tanδ — loss tangent, or damping coefficient. How quickly vibration energy is absorbed internally. Lower tanδ means less damping, a longer sustain, a note that rings on. Higher tanδ means the note is killed faster. For musical use a low tanδ is usually desirable. Measured from the width of the resonance peak in the frequency response.
ACE — acoustic conversion efficiency. The headline number, defined as E’/ρ divided by tanδ. The efficiency with which the material converts mechanical impact into audible sound. Song et al.’s key finding: eight-year-old moso carries an ACE of 1,356, some thirty-six per cent higher than two-year-old bamboo at 997. Biological age, in other words, is measurably decisive.
E’/G’ — ratio of elastic modulus to shear modulus. A measure of anisotropy — how differently the material behaves along the grain versus across it. A higher ratio correlates with better acoustic projection. For reference, spruce for violin tops sits at E’/G’ around 10–20.
acoustic properties by excitation surface
| Surface | E’/ρ (GPa·cm³/g) | tanδ | ACE (m⁴/kg·s) | E’/G’ |
|---|---|---|---|---|
| Outer wall (bamboo-green) | 20.37 | 0.0156 | 1,307 | 8.21 |
| Inner wall (bamboo-yellow) | 19.63 | 0.0161 | 1,219 | 8.45 |
The outer (fibre-dense) wall is more acoustically efficient. The inner (parenchyma-rich) wall damps slightly more. Struck from the outside, a bamboo tube reads brighter and projects further; struck from, or through, the inner wall, the sound is warmer and shorter. Song et al. frame this as the “soft-hard functional gradient” that gives bamboo its timbre.
acoustic properties by culm position
| Culm position | ACE trend |
|---|---|
| Bottom (0–1.6 m from ground) | Highest ACE — optimal acoustic performance |
| Middle | Moderate ACE |
| Top | Lowest ACE |
how it was measured
The equipment list: a dynamic mechanical analyser (TA Instruments Q800) for the vibration measurements; a field-emission scanning electron microscope for microstructure; an X-ray diffractometer for cellulose crystallinity; FTIR spectroscopy for chemical composition. Specimens were cut into standardised strips, typically 150 × 10 × 2 mm, some from the outer surface, some from the inner. Sample counts ranged between five and ten per condition.
what can be replicated in the field, and what cannot
What cannot be replicated in a field setting: the DMA (a ₹20–50 lakh instrument), the SEM, the XRD, the FTIR. These are laboratory instruments.
What can be replicated in principle: the same physical relationships, expressed in field-grade units.
- Instead of E’/ρ from a DMA, measure fundamental frequency (f₀) with Spectroid. Frequency is directly related to the stiffness-to-density ratio through f ∝ √(E·I / ρ·A·L⁴). Recorded alongside the specimen’s length, diameter, wall thickness, and weight, f₀ captures the same relationship the DMA captures — in hertz rather than GPa·cm³/g.
- Instead of tanδ from resonance peak analysis, measure decay time (T₆₀): the interval in which the struck sound fades by 60 dB. Short decay indicates high damping, long decay low damping. In Audacity: find the peak, find the point at which amplitude has dropped to 0.1 per cent of peak, that is approximately –60 dB.
- Instead of ACE from DMA data, derive a field proxy: (f₀ × amplitude) / decay_rate, or, at its simplest, rank specimens perceptually on brightness and sustain — which is the perceptual equivalent of the computed value.
study 2 — song et al., humidity effects
Song, J. et al. (2022) ‘Effect of environmental humidity on the acoustic vibration characteristics of bamboo’, Forests, 13(2), 329.
Species: Phyllostachys pubescens again.
acoustic properties vs. moisture content
| Condition | Relative humidity | Moisture content | E’/ρ trend | tanδ trend | ACE trend |
|---|---|---|---|---|---|
| Optimal | 35 % RH | ~6 % MC | Maximum | Minimum | Maximum |
| Moderate | 55 % RH | ~8 % MC | Decreasing | Increasing | Decreasing |
| High | 85 % RH | ~12 %+ MC | Minimum | Maximum | Minimum |
The finding: bamboo sounds best when dry, around 6 per cent moisture content at 35 per cent RH. As humidity rises, acoustic quality degrades — specific modulus falls, damping rises, ACE drops. This is the physical reason traditional makers dry their bamboo with patience, and the reason a bamboo instrument sounds different in monsoon than in the dry months.
The paper also compares the two wall regions under humidity cycling. The outer, fibre-dense region is more resistant to humidity-driven changes; the inner, parenchyma-rich region is more sensitive, degrading faster as moisture rises.
implication for the mizoram work
Song et al. ran this in a laboratory climate chamber. An equivalent Mizoram record — the same specimen, measured monthly across monsoon and dry season — would be messier but more ecologically meaningful. Record temperature and humidity alongside every acoustic measurement.
study 3 — song et al., heat treatment effects
Song, J. et al. (2025) ‘Mechanism by which heat treatment influences the acoustic vibration characteristics of bamboo’, Materials, 18(23), 5335. Song, J. et al. (2022) ‘An environmentally friendly and efficient method to improve the acoustic vibration performance of bamboo for musical instruments: nitrogen-protected heat treatment’, Industrial Crops and Products, 185, 115117.
Species: Phyllostachys pubescens, Phyllostachys nigra, Bambusa ventricosa.
acoustic properties vs. heat treatment
| Treatment | E’/ρ change | tanδ change | ACE change |
|---|---|---|---|
| Control (untreated) | baseline | baseline | baseline |
| 160 °C, 3.5 h (nitrogen) | +2.0 % | –30.4 % | +37.0 % |
| 190 °C, 2.5 h (nitrogen) | –1.5 % | +12.3 % | –14.2 % |
| 220 °C, any duration | Significant decrease | Significant increase | Major decrease |
The finding: mild heat treatment at 160 °C improves acoustic quality markedly — ACE rises by around thirty-seven per cent, driven mainly by a thirty per cent drop in damping. The mechanism has three strands: the degradation of hygroscopic hemicellulose (which reduces moisture sensitivity), the reduction of starchy extractives in parenchyma cells (which opens pore pathways for vibration), and a tightening of cellulose microfibril alignment (which reduces internal friction). Push the temperature to 220 °C and the cellulose itself begins to degrade; the acoustic properties collapse.
implication for the mizoram work
Fermentation with zu (the local rice-beer starter) is a biological analogue of what heat treatment achieves physically. Heat removes hemicellulose by thermal decomposition; zu fermentation may remove or modify hemicellulose by microbial action. If the fermentation produces even a fraction of the acoustic improvement that 160 °C heat treatment produces, the finding is significant: a traditional, low-tech, zero-energy biological process achieving, in principle, what industrial heat treatment requires a furnace and nitrogen gas to do.
study 4 — sinin et al., bamboo guitar acoustics
Sinin, H.M. et al. (2025) ‘Acoustic characteristics of bamboo-based guitar — a case study’, BioResources, 20(1), 1156–1170.
Species: Gigantochloa scortechinii (semantan), Malaysia.
A different approach. Rather than material-level properties, Sinin et al. measured instrument-level acoustics — a complete bamboo guitar compared against a conventional wooden guitar, through fast Fourier transform (FFT) analysis.
frequency-response comparison
| Frequency band | Bamboo guitar SPL | Yamaha guitar SPL | Difference |
|---|---|---|---|
| Low (80–250 Hz) | (values) | (values) | Bamboo is lower by x dB |
| Mid (250–2,000 Hz) | (values) | (values) | Comparable |
| High (2,000–8,000 Hz) | (values) | (values) | Bamboo is brighter by x dB |
Methodology: recordings in a semi-anechoic environment; a PicoScope oscilloscope to capture the waveform; FFT analysis in Adobe Audition to decompose the sound into frequency components; comparison across frequency spectrum, amplitude envelope, and harmonic structure.
This is closer to what a field workstation can reproduce. The requirements are a consistent striking method (standardised mallet, repeatable force), a clean recording (a Zoom H1n at a fixed distance), and FFT analysis (Spectroid in real time, Audacity for post-hoc detail). The output — spectrograms and frequency-response curves — is the visual equivalent of Song’s numerical tables. Both are legitimate acoustic characterisation; they differ in representation, not substance.
study 5 — angklung acoustic studies
Sinin, H.M. et al. ‘Study on vibro-acoustic characteristics of bamboo-based angklung instrument’, BioResources. Baskara, M. et al. (2019) ‘Acoustic characteristics analysis of angklung as Indonesian traditional music instrument’, Journal of Physics: Conference Series.
Species: Bambusa vulgaris and other Indonesian bamboos.
angklung tube tuning
| Tube | Intended note | Target f₀ (Hz) | Measured f₀ — long tube | Measured f₀ — short tube | Deviation (cents) |
|---|---|---|---|---|---|
| C5 | C5 | 523.3 | (measured) | (measured) | (calculated) |
| D5 | D5 | 587.3 | (measured) | (measured) | (calculated) |
| E5 | E5 | 659.3 | (measured) | (measured) | (calculated) |
| F5 | F5 | 698.5 | (measured) | (measured) | (calculated) |
| G5 | G5 | 784.0 | (measured) | (measured) | (calculated) |
| A5 | A5 | 880.0 | (measured) | (measured) | (calculated) |
| B5 | B5 | 987.8 | (measured) | (measured) | (calculated) |
| C6 | C6 | 1,046.5 | (measured) | (measured) | (calculated) |
PicoScope to record, FFT to identify fundamentals and overtones. The methodological detail to carry across: when both tubes are played simultaneously, the pitch is slightly different from either tube alone — the two tubes couple acoustically and create beating effects.
This is the closest existing instrument to the cheraw hybrid. A tuned bamboo percussion idiophone. The data format — intended note, measured frequency, deviation in cents — is the shape an instrument-tuning table for Mautak should take. The methodology (FFT analysis of individual tubes, then of the coupled pair) applies directly to strike elements and the crossing-pole mechanism.
study 6 — spycher et al., the treatment-comparison model
Spycher, M., Schwarze, F.W.M.R., Steiger, R. (2008) ‘Acoustic properties of modified wood under different humid conditions and their relevance for musical instruments’, Applied Acoustics, 69(6), 554–564.
Species: not bamboo — various woods (ash, birch, beech, maple, pine, spruce). But this is the gold standard for the format of a treatment-comparison table.
multi-treatment acoustic comparison
| Material | Treatment | ρ (kg/m³) | EMC (%) | E’/ρ (GPa·cm³/g) | tanδ (×10⁻³) | c (m/s) | R (m⁴/kg·s) | ACE (m⁴/kg·s) |
|---|---|---|---|---|---|---|---|---|
| Spruce (reference) | None | 430 | 10.2 | 25.5 | 8.3 | 5,240 | 12.2 | 1,470 |
| Ash | Thermal | 610 | 5.1 | 16.2 | 10.1 | 3,920 | 6.6 | 653 |
| Birch | Thermal | 570 | 5.4 | 18.1 | 9.2 | 4,210 | 7.5 | 815 |
| Beech | Acetylated | 680 | 3.8 | 14.8 | 7.6 | 3,750 | 5.5 | 724 |
| Pine | Furfurylated | 510 | 8.9 | 19.4 | 11.3 | 4,620 | 8.7 | 770 |
What makes the study exemplary: multiple materials under identical conditions, for direct comparison; multiple acoustic parameters reported for each, not one number; three humidity conditions (dry, standard, wet) for every material, establishing stability; a clearly documented methodology; and a reference material (spruce for violin) included so readers can benchmark.
This is the template for the Mautak treatment comparison table — with bamboo specimens in place of the wood species, and the four treatment conditions (untreated, borax, smoke-cured, zu-fermented) in place of the chemical treatments, measured with field-grade equivalents of the same parameters.
the mautak tuning chart — the target data formats
Drawing on the studies above, the deliverables of a field-scale characterisation of Mautak take four table forms.
format 1 — physical–acoustic correlation, the primary output
One row per specimen; this is the Mautak Tuning Chart itself.
| Sample ID | Species | Age (yr) | Culm position | Treatment | Length (cm) | Diameter (cm) | Wall (mm) | Weight (g) | f₀ (Hz) | f₁ (Hz) | f₂ (Hz) | f₁/f₀ | Peak SPL (dB) | T₆₀ (s) | Spectral centroid (Hz) | Subjective tone |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| MAU-001 | M. baccifera | 7 | Basal | Untreated | 55.2 | 4.8 | 6.1 | 342 | — | — | — | — | — | — | — | — |
| MAU-002 | M. baccifera | 7 | Basal | Borax | 54.8 | 4.9 | 6.0 | 328 | — | — | — | — | — | — | — | — |
| MAU-003 | M. baccifera | 3 | Basal | Untreated | 55.0 | 4.7 | 5.8 | 310 | — | — | — | — | — | — | — | — |
| … | … | … | … | … | … | … | … | … | — | — | — | — | — | — | — | — |
| DEN-001 | D. hamiltonii | 5 | Basal | Untreated | 55.1 | 8.2 | 10.3 | 680 | — | — | — | — | — | — | — | — |
Target: a minimum of twenty rows for Mautak, five to eight per comparison species.
format 2 — treatment comparison
Matched specimens, same dimensions, different treatment; the Spycher format, applied to bamboo.
| Treatment | n | f₀ mean ± SD (Hz) | T₆₀ mean ± SD (s) | Peak SPL mean ± SD (dB) | Spectral centroid mean ± SD (Hz) | Weight change (%) | p-value vs. control |
|---|---|---|---|---|---|---|---|
| Untreated (control) | — | — | — | — | — | — | — |
| Borax–boric acid | — | — | — | — | — | — | — |
| Smoke-cured | — | — | — | — | — | — | — |
| Zu-fermented | — | — | — | — | — | — | — |
format 3 — age comparison
The Song age table, in field-grade measurements.
| Age class | n | f₀ mean ± SD (Hz) | T₆₀ mean ± SD (s) | Peak SPL mean ± SD (dB) | Spectral centroid mean ± SD (Hz) | Wall thickness mean ± SD (mm) | Weight mean ± SD (g) |
|---|---|---|---|---|---|---|---|
| 1–2 years | — | — | — | — | — | — | — |
| 3–5 years | — | — | — | — | — | — | — |
| 5–8 years | — | — | — | — | — | — | — |
format 4 — instrument tuning accuracy
The angklung format.
| Element | Target note | Target f₀ (Hz) | Measured f₀ (Hz) | Deviation (cents) | Length (cm) | Diameter (cm) | Age (yr) | Culm position |
|---|---|---|---|---|---|---|---|---|
| E1 | C4 | 261.6 | — | — | — | — | — | — |
| E2 | D4 | 293.7 | — | — | — | — | — | — |
| E3 | F4 | 349.2 | — | — | — | — | — | — |
| E4 | G4 | 392.0 | — | — | — | — | — | — |
Deviation in cents = 1200 × log₂(measured/target). Within ±50 cents is musically acceptable for most percussion contexts.
figures
Drawing on Song, Sinin, and Spycher, the figures a publishable record needs:
- Figure 1 — scatter plot of f₀ against internode length, one point per specimen, colour-coded by age class, with a regression line and R². The most fundamental relationship in the dataset: longer tube, lower pitch.
- Figure 2 — bar chart of T₆₀ by age class, three groups with error bars. The “older bamboo sounds better” visualisation.
- Figure 3 — bar chart of acoustic parameters by treatment condition, four groups (untreated, borax, smoke, zu), each normalised to the control. Shows at a glance which treatments moved which parameter, and in which direction.
- Figure 4 — spectrogram comparison of cheraw clap against mallet strike, two panels, same time window. The clap should show broader bandwidth and visible friction harmonics.
- Figure 5 — spectrogram comparison of untreated against zu-treated bamboo. If the treatment changed the overtone pattern or the decay envelope, it will be visible.
measurement crosswalk — laboratory to field
| Parameter | Song’s method | Field method | Equipment |
|---|---|---|---|
| Fundamental frequency (f₀) | DMA resonance | Spectroid + FFT in Audacity | Phone + Zoom H1n |
| Overtones (f₁, f₂) | DMA higher modes | FFT peak identification in Audacity | Zoom H1n + laptop |
| Damping (tanδ) | Resonance peak half-width from DMA | Decay time T₆₀ from waveform envelope in Audacity | Zoom H1n + laptop |
| ACE | E’/ρ ÷ tanδ from DMA | Proxy: (f₀ × amplitude) / decay_rate, or perceptual rank on brightness and sustain | Phone + recording |
| Density | Laboratory balance + volume | Kitchen scale ÷ estimated volume from caliper and tape | Scale + caliper |
| Spectral centroid | Computed from DMA frequency response | Computed from FFT in Audacity (amplitude-weighted mean frequency) | Laptop |
| Peak SPL | Calibrated microphone, anechoic chamber | Zoom H1n at fixed 30 cm distance — relative comparison between specimens, not absolute calibration | Zoom H1n + tripod |
On precision: field measurements are less precise than laboratory measurements. This is worth stating in the limitations section of any paper. The relationships recovered — that older bamboo has a longer decay, that basal position carries a higher spectral centroid, that zu treatment alters the overtone pattern — remain valid regardless of absolute precision, because the comparisons are between specimens under identical conditions, not against an external standard.
the gap map
| What exists | Species | Region | What is missing |
|---|---|---|---|
| Song 2023: ACE, E’/ρ, tanδ by age, surface, height | Moso (P. pubescens) | China | No South Asian species; no Melocanna |
| Song 2022: humidity effects | Moso | China | No field-condition data — no real seasons, only a climate chamber |
| Song 2025: heat-treatment effects | Moso, P. nigra, B. ventricosa | China | No biological treatment, no fermentation, no traditional methods |
| Sinin 2025: guitar frequency response | Semantan (G. scortechinii) | Malaysia | Instrument-level only; no raw-tube data |
| Angklung studies: tube tuning | B. vulgaris, various | Indonesia | No species-to-species comparison; no material library |
| Spycher 2008: treatment-comparison format | Various woods | Europe | No bamboo; method only |
| Schwarze et al. 2008: fungal treatment of violin wood | Spruce | Switzerland | Only wood, not bamboo; only fungal, not fermentation |
what the mautak tuning chart is a first for
- First acoustic data for Melocanna baccifera, and for a South Asian bamboo species
- First field-condition seasonal acoustic monitoring — real monsoon, not climate chamber
- First biological treatment (zu fermentation) effect on bamboo acoustic properties
- First raw-tube acoustic library for any bamboo species
- First species-to-species acoustic comparison for South Asian bamboo
- First documentation of cheraw percussion acoustics — broadside-clap spectrum
- First application of fermentation, a traditional low-tech process, as acoustic tuning
Seven open cells. The publishable contribution is the closing of them.
This reference is a working document. Corrections, additions, and new papers are integrated as they appear; the page is re-dated on substantive revisions.
references
Baskara, M. et al. (2019). Acoustic characteristics analysis of angklung as Indonesian traditional music instrument. Journal of Physics: Conference Series.
Schwarze, F.W.M.R., Spycher, M., Fink, S. (2008). Superior wood for violins — wood decay fungi as a substitute for cold climate. New Phytologist, 179(4), 1095–1104.
Sinin, H.M. et al. (2025). Acoustic characteristics of bamboo-based guitar — a case study. BioResources, 20(1), 1156–1170.
Sinin, H.M. et al. Study on vibro-acoustic characteristics of bamboo-based angklung instrument. BioResources.
Song, J. et al. (2022). Effect of environmental humidity on the acoustic vibration characteristics of bamboo. Forests, 13(2), 329.
Song, J. et al. (2022). An environmentally friendly and efficient method to improve the acoustic vibration performance of bamboo for musical instruments: nitrogen-protected heat treatment. Industrial Crops and Products, 185, 115117.
Song, J. et al. (2023). Scientific mechanism of bamboo acoustic vibration performance from structure-chemical perspective. Industrial Crops and Products, 200, 116817.
Song, J. et al. (2025). Mechanism by which heat treatment influences the acoustic vibration characteristics of bamboo. Materials, 18(23), 5335.
Spycher, M., Schwarze, F.W.M.R., Steiger, R. (2008). Acoustic properties of modified wood under different humid conditions and their relevance for musical instruments. Applied Acoustics, 69(6), 554–564.