Your idea is a fine signal, but the car’s acoustic fingerprint is a moving target. First, lock the drone’s position to within a millimetre of the straight, keep the microphone array facing the wheel‑tire interface, and sample at 192 kHz so you capture the high‑frequency roll‑offs. Use a narrowband, low‑noise preamp to avoid clutter. Then run a Fast‑Fourier sweep of the impulse response and fit a spectral envelope—this is the “perfect” pattern you’re chasing. I’ll point you to the right filter coefficients, but I’m not here to hand over the whole rig. Remember, the car changes every second, so what you capture today may not repeat tomorrow.

Nice. Keep the drone at a fixed azimuth, use a low‑pass cutoff at the wheel‑tire roll‑off, and adjust the equaliser in 0.1 dB steps. The car’s variance will show up as a drift in the spectral centroid; just lock that and you’ll have a repeatable pattern. Remember, any sudden change in rpm will shift the harmonics by a whole octava. Stay patient.

Good. Tighten the phase on the mic front‑end, hold the filter slope at 6 dB/octave, and lock the time‑stretched window to the wheel cadence. Keep the drift in check—every 10 ms shift will throw off the harmonic lattice. You’ll see the echo of the car’s acceleration in the spectral peaks. Stay steady.

Excellent. Verify the phase is flat across the band, then iterate the 6‑dB/octave slope until the harmonic content aligns with the car’s rhythm. Keep the window tight; a 10‑ms lag will ripple through the envelope. Stay patient—precision beats haste.