The acoustic performance of Sonic Crystal Noise Barriers (SCNBs) is strongly influenced by the angle-dependent nature of their transmission behaviour, which challenges the interpretation of standardized measurement methods. The present work focuses on the numerical emulation of three assessment procedures: the diffuse-field method (EN 1793-2), the direct-field in situ method (EN 1793-6), and a horizontal-incidence approach proposed here to more realistically represent conditions near linear noise sources such as roads and railways. In order to reproduce these measurement scenarios with controlled precision, three finite-difference time-domain (FDTD) implementations of periodic boundary conditions (Multiple Unit Cells, Sine–Cosine, and Transformed Field) are examined and applied to both a homogeneous reference layer and a representative sonic crystal barrier. The findings indicate that the assumed incidence distribution exerts a substantial influence on the estimated insulation. The in situ normal-incidence method substantially overestimates the Transmission Loss in frequency ranges governed by Bragg scattering, while the diffuse-field and horizontal-incidence methods yield comparable and more realistic values. It is evident that, among the numerical techniques, the Transformed Field method provides the most efficient and accurate broadband tool for conducting these emulations over wide angular ranges. The study demonstrates that an efficient, angle-resolved numerical emulation of measurement methods is essential to avoid mischaracterizing the sound insulation of SCNBs and to bridge the gap between laboratory protocols and real-world acoustic exposure.
Immersive audio formats compete for adoption, yet objective comparisons across them remain limited, and the behaviour of the objective models under cross-format conditions is largely uncharacterised. This study applies two binaural models, BAM-Q (perceptual quality) and BINAQUAL (localization similarity), to binaural renderings of 11 format variants derived from 3 professional recordings differing in genre and Ambisonic provenance, under three reference anchors and with a controlled test of stimulus alignment. Two properties of the evaluation influence the outcome more strongly than many format differences, and affect the two models differently. First, immersive renderers impose transport delays up to 510 ms that are not quality degradations; because BINAQUAL compares phase representations, leaving them uncompensated makes its score track delay rather than fidelity (ρ=−0.86), and correcting them changes localization similarity by a median of 149.3%. BAM-Q, operating on modulation-domain representations, is unaffected (median 0.0%). Second, under BINAQUAL the apparent advantage of one format family over another depends on the reference anchor, reversing in all 3 items when the channel-based anchor replaces a scene-based one; the BAM-Q composite never reverses. With aligned stimuli the models are moderately correlated (r=0.51), not independent. Format orderings are reproducible across content (Kendall’s W=0.94 for localization similarity, permutation p<0.001). The results yield prescriptions for cross-format evaluation (compensate and report latency, treat the anchor as an experimental factor, refer cue measures to discrimination thresholds) and identify subjective validation as the next step.
