Spectral Silences in Raman Spectroscopy of Tooth Enamel

Raman measurements of tooth enamel contain intense mineral bands together with weaker contributions that may be difficult to distinguish from fluorescence, baseline structure and stochastic noise. This methodological paper defines “spectral silence” as an operational property of a specified Raman measurement and preprocessing pipeline: a spectral window in which residual signal remains small relative to a documented noise estimate. The framework combines explicit masking, fixed baseline estimation, robust noise estimation from first differences, and a windowed silence score S*(W) based on the 90th percentile of absolute residual amplitude. The revised contribution is deliberately methodological and does not claim a universal silent interval for enamel. Instead, it establishes a reproducible language for reporting quiet spectral space and a prespecified validation strategy that can be executed by laboratories with access to enamel Raman spectra. To demonstrate mathematical behavior without fabricating experimental observations, a fully reproducible simulation was performed on a 200–3200 cm −1 synthetic spectrum containing representative phosphate/carbonate bands, baseline curvature, Gaussian noise and isolated spikes. The simulation used a fixed random seed (42), 200 trials per amplitude, and controlled weak‐line injections. The matched‐filter benchmark achieved an AUC of 0.925, compared with 0.800 for the conventional local‐SNR benchmark; both decision thresholds were calibrated to a nominal 5% false‐positive rate from independent zero‐amplitude simulation trials, and the empirical zero‐amplitude false‐positive rate was 0.050 for both methods. The study therefore provides a quantitative proof‐of‐concept and a complete empirical validation protocol, while explicitly separating what has been demonstrated computationally from what remains to be tested experimentally.