Bibliographic record
Abstract
This paper investigates theoretically how duct geometry and liner thickness affect the attenuation of fundamental-mode sound propagation in a lined duct.The study was done to satisfy the need for a greater understanding of interior naturalventilation openings and of silencers implemented to improve the acoustical performance ('ventilators'), and to provide engineers and architects with optimal-design guidelines.It assumed ventilators of the simplest formstraight, acousticallylined ducts of rectangular cross-section.An analytical solution is presented for the attenuation of the fundamental mode in such a duct.Duct-liner thickness does not affect high-frequency performance; however, it limits low-frequency performance.A 25-mm liner is likely not thick enough to be effective, but a 100-mm liner may be excessive.Increasing the duct height reduces the attenuation at all frequencies; in order to provide effective attenuation through the 4000-Hz band, the height should not exceed 100 mm.If the cross-sectional aspect ratio of a duct is greater than 10, or the duct is only lined on two opposing surfaces, the attenuation of its fundamental mode is in effect identical to that of a 2D lined duct.Provided that the duct liner and height are such that the silencer is effective at absorbing sound at a given frequency, reducing the aspect ratio towards unity will result in large attenuation gains. RSUMCet article tudie l'influence thorique de la gomtrie d'un conduit et de l'paisseur d'un revtement acoustique sur l'attnuation acoustique du mode fondamental.L'tude vise une meilleure comprhension des ouvertures dans les cloisons internes et des silencieux conus pour amliorer la performance acoustique, afin d'informer les ingnieurs et les architectes des conceptions optimales.Elle fait l'hypothse de silencieux de formes simples: un conduit rectangulaire avec un revtement acoustique interne.Une solution analytique est prsente pour l'attnuation du mode fondamental de ce type de conduit.L'paisseur du revtement n'influence pas sur les performances hautes frquences; cependant, elle limite celles basses frquences.Un revtement d'une paisseur de 25 mm n'est pas efficace, mais 100 mm peut tre excessif.Augmenter la hauteur du conduit rduit l'attnuation pour toutes les frquences; dans le but d'obtenir une attnuation efficace aux frquences suprieures 4000 Hz, la hauteur ne devrait pas dpasser 100 mm.Si le rapport des dimensions latrales du conduit est suprieur 10, ou si seulement deux surfaces opposes portent un revtement, l'attnuation du mode fondamental est gale celle d'un conduit 2D.Tant que le revtement et les dimensions du conduit sont tels que le silencieux 2D absorbe efficacement le son une frquence particulire, une rduction du rapport rsultera en une attnuation plus importante.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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 teacher head, 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".