Equalization in ambisonics

In ambisonics, the number of loudspeakers must be greater than or equal to the requirement of the ambisonic order. On the one hand, if the number of loudspeakers in an ambisonic system satisfies the minimum requirement exactly, localization in the lateral regions can be poor. On the other hand, the use of a large number of loudspeakers in an ambisonic array induces spectral impairments. In this paper, we present a binaural ambisonic decoder equipped with a 1/3-octave equalizer that demonstrates how to improve sound localization without perceptual spectral impairment. The equalization decoding estimates the level of spectrum impairment in a virtual high-density loudspeaker array and uses a 1/3-octave filterbank to equalize the frequency components, which are low-pass filtered or comb filtered. Therefore, the magnitude of the treated signal is nearly uniform from low to high frequencies. Both objective and subjective listening tests were conducted. The experimental results show that the proposed method reinforces sound localization, especially at low frequencies. Additionally, the use of a 1/3-octave filterbank facilitates the higher-order extension of binaural ambisonic decoding.