In wearable sports analytics, the "Swing Score" metric quantifies how consistently a player replicates their ideal biomechanical pattern. Our initial deployment relied on standard industry frequency-domain filtering (Butterworth) to handle sensor noise.
The Anomaly: While noise was successfully reduced, high-velocity swings were receiving lower consistency scores than expected. Additionally, impact acceleration data—the "snap" of the club hitting the ball—was registering near zero, which is physically impossible.
A golf impact is a Transient Event (an impulse lasting < 0.5ms). Standard frequency-based filters treat this sharp spike as "high-frequency noise" and smooth it out. We were essentially erasing the most critical moment of the athletic movement in our pursuit of clean data.
Drawing on continuum mechanics principles regarding transient signals, we re-architected the processing pipeline. We moved from a frequency-domain approach (blindly cutting high frequencies) to a Time-Domain approach that preserves local signal geometry.
By implementing local polynomial smoothing filters (Savitzky-Golay), we maintained signal-to-noise ratios while preserving the high-frequency "edges" that define the club's impact with the ball. Furthermore, we decoupled the "Ideal Reference Curve" calculation, ensuring that the player's baseline for comparison is mathematically pure rather than artificially smoothed.
The updated algorithm was validated against a dataset containing both "Valid" (Pro-level) swings and "Erroneous" (Amateur/Bad) swings.
Lower Swing Score = Higher Consistency. Lower NRMSD = Better Data Fit.
| Metric | Legacy Model | New Model | Improvement |
|---|---|---|---|
| Swing Score | 6.2 ± 1.2 | 4.5 ± 1.2 | +28.4% |
| Fit Error (NRMSD) | 0.123 | 0.089 | -27.8% |
| Impact Force | ~0 m/s² (Lost) | 53.8 m/s² | Data Recovered |
Crucially, the new algorithm does not artificially improve bad swings. When tested against the "Erroneous" dataset, the model correctly identified poor consistency, maintaining a high Swing Score (10.0), confirming that the improvements are physically genuine and not just a lowering of the baseline.