An additional configuration to standard ASTM E2611-09 for measuring the normal incidence sound transmission loss in a modified impedance tube
Bibliographic record
Abstract
This paper presents a three-microphone two-load (3M2L) method for measuring the normal incidence sound transmission loss of a noise control system or material in a modified impedance tube. In the standard ASTM E2611-09, the downstream section of the impedance tube includes two microphones flush with the interior surface of the tube and the proposed four-microphone two-load (4M2L) method to assess the normal incidence sound transmission loss requires the use of two arbitrary acoustic terminations. The method presented here is conceptually identical but (i) the downstream section is reduced to a simple movable rigid backing with one microphone flush mounted on it and (ii) the two arbitrary acoustic terminations are replaced by two air cavities. It thus requires one microphone less and fewer transfer functions. The standard switching technique used to correct the variations between microphones is validated on a symmetrical air layer. The proposed 3M2L method is then applied to a non-symmetrical non-homogenous specimen and validated compared to the standard 4M2L method.
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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 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.010 | 0.004 |
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".