Calibration of sound power sources: Current status and new developments

Reference sound sources used in sound power measurements are currently calibrated according to well-documented techniques. Low frequency limitations and solely broadband analysis restrict the applicability of these methods. The concept of traceability is introduced to overcome these deficiencies. This study presents the calibration of reference sound sources through a measurement chain, which is based on the substitution method. The applicability of the substitution method extends to sound intensity measurements and narrowband frequency analysis. A specially designed apparatus allows the detection of the sound field over a fully scanned hemisphere. The results of the apparatus are comparable to the results of the existing methods. The substitution method reduces the required corrections, which are presented. The sound power levels are supplemented by a transparent uncertainty budget, which allows the estimation of each uncertainty component individually. The comparison between the methods is also given in terms of a confidence interval.