Verification of prediction based on randomized tail-corrected cone-tracing and array modeling

Abstract

A new room acoustics prediction method, randomized tail-corrected cone-tracing (RTC), is described together with sample prediction/measurement comparisons. RTC is the result of ten years of experience using the image source model, ray- and cone-tracing, and combines elements of all three methods. RTC is a robust number-prediction method, including the effects of frequency-dependent diffuse reflection for both early and late reflections, as well as a method that creates echograms suitable for binaural post-processing and auralization. Further, a WIN32 DLL directivity interface (DDI) is described. The interface is general and is capable of arbitrary data-format translation and accurate distance-dependent high-resolution array modeling including beam steering. The array modeling is either made via a generic DDI module or via modules custom designed based on detailed manufacturer array specifications (transducer placement, directivity pattern, aim, weighting filter, and delay). Sample prediction/measurements comparisons are given for DSP-controlled column arrays under free-field conditions, in a large railway station and in a large church. It is demonstrated that the common fixed measurement distance 10-deg full space data is insufficient for modeling arrays both due to the limited angular resolution and because far-field conditions may not be reached until 30 m distance or beyond.