Experimental study of propeller-aircraft run-up noise
Bibliographic record
Abstract
Measurements were made of the characteristics of the noise radiated by a Beechcraft 1900D twin-propeller aircraft during engine run-up. The objective was to determine the feasibility of controlling this noise using active noise control. Total noise levels varied with aircraft heading from 103 to 112 dB (100 to 109 dBA) at 73 m from the aircraft. Noise directivity plots were generated. Levels at the nearest community 3 km away varied from 74 to 77 dB (62 to 66 dBA). Near the aircraft the noise spectra comprised a series of equally-high peaks at the 112-Hz fundamental frequency and its multiples. In the community, the three lowest peaks dominated the A-weighted spectrum, with higher-frequency peaks being progressively attenuated. A coherence analysis was performed on the noises measured at 73 m and 98 m from the aircraft. The insertion loss of a blast fence near the run-up area was estimated from run-up noise measurements made on both sides of the fence. The insertion loss varied from 4 to 13 dB and was greatest at mid frequencies.
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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 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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 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".