This study investigates the perceptually sufficient ambisonic order for beamforming in complex acoustic scenes, defined as the minimum spatial resolution above which no audible improvement is perceived. Two beamforming methods were evaluated: hypercardioid and MVDR beamforming. In contrast to previous studies, the case of an ideal microphone array was considered, in order to the evaluate the beamforming methods independently of ambisonic encoding error. Sound scenes were generated using room acoustic simulations and encoded into ambisonic signals. A perceptual evaluation was conducted using a three-interval/two-alternative forced choice (3I/2AFC) test design with an adaptive procedure. The experiment used a production-constrained reference (7th-order) and a high-order reference (19th-order). Results showed that the required order would depend on the beamforming method and characteristics of the sound scene. Diffuseness profiles can be used to analyze the influence of the ambisonic order on the sound field diffuseness and to evaluate whether the directional information available is sufficient to support effective adaptive beamforming.
