Octavia IV Combi 2.0 TDI — 129 Hz droning above 125 km/h, temperature-dependent

Hi all,

I'm chasing a wind/resonance noise on my 2025 Octavia IV Combi 2.0 TDI 150 DSG and hoping someone here has seen the same.

Symptoms:

- A droning/booming sound that starts around 125 km/h and gets louder with speed.

- It's strongly temperature-dependent: only appears above ~25 °C outside. On cooler days it starts much later (140+) or not at all.

- Sounds like it comes from the front. Headwind makes it worse; drafting behind another car makes it disappear.

- It was NOT there for the first few months — it appeared later.

I recorded it and ran a frequency analysis. It's a narrow tonal peak at exactly 129 Hz. The frequency stays fixed at 129 Hz regardless of speed — only the loudness changes. It also continues unchanged when I shift to neutral and coast, so it's not linked to engine revs.

What I've already ruled out myself:

- Tyres: swapped the complete wheel set (summer Hankook → winter Michelin). Noise still there, same 129 Hz.

- Wheel bearings (no change when swerving), balance (factory, smooth), ventilation (no change with recirculation or fan off), roof bars (removed).

- Taped over many seams: hood seal, plenum cover, headlight gaps, windscreen sides, front of the roof rails — no change.

The fixed frequency + temperature dependence + speed relationship all point to an aerodynamic cavity resonance to me, rather than anything mechanical.

Two questions:

1. Has anyone had this and actually solved it?

2. I've noticed everyone I've found online with this exact symptom has the Combi (estate). Can anyone with a hatch/liftback confirm whether they get it too, or is this a wagon-specific thing?

Thanks in advance — happy to share the frequency plot once my account can post images.