Bibliographic record
Abstract
This paper deals with the classical problem of transmission-reflection and modes conversion due to the presence of acoustic liners in duct.The model consists of an infinite rectangular duct with an unlined and lined section.The approach is based on the modal calculation of the total acoustic sound power in a duct by the determination of the modal coefficients of the transmitted waves at the impedance discontinuity junc tion.For a given propagating mode (plane wave or higher order mode), incident from the rigid duct, the total sound power is calculated in the lined section by summing the acoustic power over all generated modes.The example studied here shows how the conversion affects the nature of the incident mode as a function of the admittance of the liner, frequency and mode number.It also allows for the quantification of the attenuation provided by an acoustic duct liner. SOMMAIRELe recours a des revêtements de parois absorbants le long d'un conduit est un moyen naturel de réduire le bruit généré par des machines tournantes (turboréacteurs, circuits de ventilation, etc.).D'un point de vue scientifique, ce contexte pose plusieurs problèmes fondamentaux tant sur le plan de la compréhension des phénomènes que sur celui de leur modélisation.Il faut en effet pouvoir préciser les aspects liés à la propa gation guidée en présence de parois absorbantes.Cet article s'inscrit dans ce contexte et discute les effets liés à la conversion des modes qui est causée par la présence d'une discontinuité d'impédance en conduit.Pour ce faire, un model de conduit infini tridimensionnel a été étudié ou une partie est traitée par un revête ment acoustique.L'approche est basée sur un calcul modal de la puissance acoustique en conduit après détermination des coefficients modaux des modes transmis.Pour un mode de propagation donné (ondes planes ou modes supérieures), dans la section rigide du conduit, la puissance acoustique totale est calculée dans la section traitée en sommant les puissances des modes générés par la discontinuité d'impédance.L'exemple étudié ici montre comment cette conversion affecte la nature du mode incident en fonction de l'impédance du revêtement acoustique, de la fréquence et du mode.Il permet aussi de calculer l'atténuation apportée par un revêtement acoustique en conduit.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".