On the Impact of Neglecting Accurate Sound Speed-Models on the Cylinder Measurement Method for Directivity Balloons

Dec 2023 | Education Resources

The far-field acoustical transfer function of an electroacoustic device, such as a loudspeaker, is of fundamental importance in acoustic modelling software to predict the resulting sound field produced by multiple devices in 3D space. This dataset, commonly known as a directivity balloon, is usually acquired through time-consuming, sophisticated measurement techniques involving extensive hardware and dedicated post-processing algorithms. Additionally, such dataset is usually compensated for the effect of acoustical propagation to reference the magnitude and phase values to conventional distances. This works investigates the effects of propagation compensation within the cylinder measurement method for directivity balloons, specifically considering the use of improper sound speed values relative to the ambient conditions during the measurement process. The importance of employing environmental parameter-dependent models for the propagation speed of sound in this type of measurement is emphasized, as to maintain high accuracy in the final directivity data phase response.