Producing a High Level Harmonic Acoustic Pressure Field with Harmonic Acoustic Pneumatic Source (HAPS): Experimental Validation of the Harmonic Distortion Reduction
Bibliographic record
Abstract
Applications such as active control of fane noise, require high Sound Pressure Levels (SPL). Pneumatic acoustic sources are usually used for that purpose (e.g. the WAS 3000 and the Mark VI and VII). The harmonic acoustic pneumatic sources (HAPS) - which use the chopping of an airflow to generate an acoustic pressure field - are being studied for applications requiring high-level harmonic acoustic pressure fields. A recent study has shown that the amplitude, phase, and frequency generated by HAPS are accurately controllable, and can reach 120 dBSPL. However, higher harmonics are also generated at high SPL and this could be detrimental to the intended applications (e.g. active control of tonal noise). An experimental campaign dedicated to understanding the harmonic distortion of HAPS has been conducted on a single HAPS in a semi-anechoic chamber. Measurements with quarter-wave tube at the output of the HAPS were also carried out to reduce this distortion. Levels of 120 to 130 dBSPL for the fundamental were reached, with a difference of 10 dB between the fundamental and the second harmonic (H1/H2 distorsion). Adding a quarter-wave tube increased the acoustic pressure level from 4 to 6 dBSPL, and the H1/H2 distorsion from 2 to 8 dBSPL.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".