The influence of positional uncertainty in free-field microphone calibration

Abstract

The positioning error of an acoustic transducer may become a relevant source of uncertainty in some circumstances, especially in the high frequency range. The issue of quantifying this uncertainty is still far from being resolved, though some efforts have been made.This paper studies positional uncertainty based on the concept of an uncertainty sphere. A general characterization of positional errors is introduced and the sound pressure uncertainty is calculated for two basic calibration scenarios where an analytical formula exists.The results show that the influence of positional uncertainty cannot be neglected. Even in the low-frequency-range (<3 kHz), it may give rise to a slight deviation that could be considered noticeable for calibration purposes. At high frequencies the consequences become dramatic, showing deviations that can exceed 5 dB for non-frontal incidence. A strong dependence is found between the output uncertainty and the source directivity pattern.For cases where an analytical solution is not available, the contribution to uncertainty can be calculated via Monte Carlo simulations. A validation and convergence study of this application of the Monte Carlo method (MCM) is presented. The results show that the method is suitable for a great variety of practical scenarios.

Study on the Evaluation Method of Sound Phase Cloud Maps Based on an Improved YOLOv4 Algorithm

“…Traditional acoustic calibration methods [6] can only calibrate the measurement characteristics of a single array element to eliminate the differences between microphone array elements. However, the errors caused by inaccurate element positions cannot be calibrated [7]. Therefore, not only is a sound imaging instrument's calibration scheme needed, but also a suitable method should be developed to assess source localization results in cloud maps.…”