Annoyance Penalty Model for Steady-State Broadband Noise with Varying Spectra

Noise regulations often apply penalties (e.g., +5 dB) to A-weighted equivalent sound pressure levels (LAeq [dB]) to account for increased annoyance from tonal or impulsive features. Psychoacoustic evidence indicates that spectral characteristics also affect annoyance, with some spectra being substantially more disturbing than others. Yet, no established method exists for determining spectrum-based penalties from measured sound spectra. This study aimed to develop a simple, objective model for assigning penalties to steady-state broadband sounds based on spectral properties. Using experimental data comprising annoyance ratings and penalties for 23 spectrally distinct broadband sounds at three LAeq levels (32, 40, and 48 dB), we evaluated several single-number noise descriptors from the literature. Room The Noise Criterion showed the strongest association with direct annoyance ratings, while the spectral centroid (SC) and sharpness were most closely related to spectrum-based penalties. Due to its simplicity, the spectral centroid was selected for the final model: k=6.9·log10(SC)−16.3. The proposed model is expected to be applicable for broadband sounds within 32–48 dB LAeq and offers a practical approach for incorporating spectral effects into noise assessment.