Exploring Virtual Sound Fields for Directivity Measurement of Smart Audio Devices

To better satisfy the measurement needs for sound acquisition directionality in smart audio devices and to enhance the flexibility, efficiency, and cost-effectiveness of measurement setups, this study explores the viability of using virtual sound fields. Virtual sound fields are synthesized via vector synthesis. The study compares virtual and physical sound sources in terms of sound field radiation directivity through sound field simulation experiments. Furthermore, an acoustic camera is used to compare the differences in directivity when capturing and localizing virtual versus real sound sources. The simulation data reveal that smaller loudspeaker angles make it easier for virtual sources to replicate the sound field radiation directivity of real physical sources. Lower frequencies increase the 'sweet spot' range, where the virtual sound field closely approximates the directivity of the real physical sound field. Practical measurement experiments demonstrate that lower frequencies in the virtual sound field align closer to the physical sound field's directivity. Specifically, with a speaker angle of 22.5° and frequencies below 2 kHz, the acoustic camera achieves azimuthal accuracy of less than 3° for virtual sound fields; however, at frequencies above 4 kHz, the camera struggles to accurately capture the azimuth of virtual sound fields. The virtual sound field proves effective for measuring directionality in mid to low-frequency ranges, offering a flexible approach to creating complex virtual acoustic environments for assessing smart audio devices.