Derivation, verification and validation of a length correction factor for folded quarter-wavelength resonators
Bibliographic record
Abstract
Acoustic metamaterials that consist of multiple λ /4-resonators in series or parallel can be tuned to realise high broadband absorption in a given frequency range. These resonators are often folded to obtain a structure with a (deep) sub-wavelength thickness, which allows an optimal use of the available space and enables low-frequency sound absorption in confined spaces. However, folding a resonator can lead to a significant change in resonance frequency, resulting in an off-design acoustic performance. Hence, in this paper, the effect of a single 90° fold on the resonance frequency of rectangle and slit-like λ /4-resonators is investigated numerically. Based on these numerical simulations, a length correction factor δ is derived to account for this effect in the analytical model. The use of the correction factor is verified for various single-fold resonator configurations and against existing length formulas. The length correction factor is then experimentally validated for rectangle resonators by means of impedance tube measurements on 3D printed samples. It is found that using the proposed length correction factor allows for an accurate prediction of the resonance frequency of the discussed resonator geometries.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".