Period indicators : 24/09/2026 – 23/10/2026
The period indicators are combined on an energy basis from the daily values rather than as a plain average: levels are logarithmic and do not add arithmetically. The figure in brackets beside the day count gives how many days are complete.
Where the indicators come from
- N65 by day and N60 by night: event counts used by the UK Civil Aviation Authority, with day 07:00–23:00 and night 23:00–07:00.
- N68 at night: the Austrian Luftverkehr-Lärmimmissionsschutzverordnung (BGBl. II 364/2012, §4) — more than six night-time peaks above 68 dB(A) trigger noise-protection measures at the airport operator's expense.
- Lden, Lday, Levening, Lnight: Directive 2002/49/EC. Annex I §3 expressly provides for supplementary LAmax or SEL indicators for night-time protection where noise peaks occur — the average indicators do not exhaust the assessment.
- All count indicators include ONLY events attributed to a specific flight. Where a strong local source exists, the total across all sources is shown alongside, so the difference is visible.
| Station | Days | Lden | LAeq,24h | Lday | Lnight | Lmax | N70 | N70/day | N70 night | N65 day | N60 night | N68 night | matched |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SPM-01 · spm-01 | 29 (26) | 66.1 | 60.7 | 60.9 | 58.8 | 99.0 |
1734
all sources: 3551
|
60 | 237 | 2714 | 892 |
293
21/29 days
|
51% |
| SPM-02 · spm-02 | 24 (21) | 63.6 | 58.1 | 58.6 | 56.7 | 97.1 |
2109
all sources: 4405
|
88 | 319 | 4000 | 829 |
447
17/24 days
|
49% |
| SPM-03 · spm-03 | 24 (22) | 73.8 | 67.9 | 67.9 | 67.0 | 107.5 |
4495
all sources: 12089
|
187 | 580 | 5718 | 884 |
675
23/24 days
|
43% |
Consistency check between instruments
For each pair of stations the SAME flights are compared. The difference explained by geometry is subtracted, leaving the unexplained difference. Between nearby stations this should be small; if it is not — and especially if the same offset also appears in the L90 background — the fault lies in the measuring chain, in calibration or in a reflecting surface beside the microphone, rather than in the environment.
| Station pair | Distance | Common flights | Δ SEL | Δ L90 | Expected | Unexplained | Status |
|---|---|---|---|---|---|---|---|
| SPM-01 → SPM-03 | 691 m | 2930 | 9.12 | 3.66 | 3.33 | 5.79 | inconsistent |
| SPM-02 → SPM-03 | 3647 m | 4265 | 4.73 | 4.68 | 2.23 | 2.51 | consistent |
| SPM-01 → SPM-02 | 4097 m | 3078 | 3.76 | -0.50 | 0.44 | 3.32 | inconsistent |
Take care with the absolute levels.
One or more station pairs show an unexplained difference above the threshold. Before the absolute levels are used in a report, an on-site check of instrument calibration, microphone mounting and local noise sources is advisable. Comparisons between days at the SAME station are unaffected.
Noise estimation model
The model is not a physical law of propagation but an interpolation calibrated on our own measurements: from the pairs of measured SEL and slant distance it derives, per aircraft type, a reference level and a common attenuation slope. It holds only within the range of distances actually measured and is not extrapolated beyond it.
| Attenuation slope | -13.71 dB/decade |
| σ (per pass) | 5.38 dB |
| MAE | 3.98 dB |
| Valid range | 108 – 4741 m |
| Samples | 14323 (33 types) |
| Computed | 23/10/2026 15:40:20 |
Source level per aircraft type (SEL @ 1000 m)
Derived solely from our own measurements. The ordering of the types is an independent check of correctness: the newer-generation models — A20N/A21N against A320/A321, B38M against B738, the 787s — should come out lower, and they do.
| Type | SEL dB(A) | Samples | SD |
|---|---|---|---|
| A332 | 89.2 | 39 | 2.8 |
| A333 | 88.5 | 121 | 4.7 |
| B772 | 88.5 | 119 | 4.0 |
| B77W | 85.7 | 364 | 3.8 |
| A339 | 84.7 | 120 | 4.2 |
| DH8D | 84.6 | 76 | 4.1 |
| B739 | 84.2 | 52 | 5.0 |
| B78X | 84.1 | 131 | 3.2 |
| B763 | 83.9 | 34 | 5.6 |
| B788 | 83.0 | 207 | 4.2 |
| B738 | 82.8 | 1232 | 4.6 |
| A359 | 82.5 | 50 | 3.4 |
| B789 | 81.8 | 133 | 3.4 |
| B734 | 81.0 | 34 | 4.9 |
| A321 | 80.8 | 770 | 5.2 |
| A319 | 80.7 | 148 | 5.5 |
| E195 | 80.6 | 24 | 2.9 |
| E190 | 80.2 | 55 | 4.4 |
| A320 | 79.6 | 3324 | 5.5 |
| A21N | 78.6 | 3131 | 5.2 |
| B38M | 77.5 | 336 | 5.6 |
| BCS3 | 77.3 | 76 | 6.6 |
| GLEX | 77.0 | 28 | 4.3 |
| A20N | 76.9 | 2027 | 5.6 |
| E55P | 76.6 | 23 | 6.7 |
| GL6T | 76.0 | 22 | 5.0 |
| CL35 | 75.8 | 58 | 7.1 |
| E35L | 75.1 | 32 | 7.4 |
| AT45 | 74.9 | 120 | 8.5 |
| AT46 | 74.8 | 108 | 6.9 |
| LJ60 | 73.8 | 20 | 5.8 |
| AT76 | 73.7 | 1283 | 6.6 |
| C56X | 73.7 | 26 | 5.6 |