Jukka Ahonen

The diffuse sound field in energetic analysis

Measuring the degree of diffuseness of a sound field is crucial in many modern parametric spatial audio techniques. In these applications, intensity-based diffuseness estimators are particularly convenient, as the sound intensity can also be used to obtain, e.g., the direction of arrival of the sound. This contribution reviews different diffuseness estimators comparing them under the conditions found in practice, i.e., with arrays of noisy microphones and with the expectation operators substituted by finite temporal averages. The estimators show a similar performance, however, each with specific advantages and disadvantages depending on the scenario. Furthermore, the paper derives an estimator and highlights the possibility of using spatial averaging to improve the temporal resolution of the estimates.

Directional audio coding - perception-based reproduction of spatial sound

Directional Audio Coding (DirAC) is a perceptually motivated technique for spatial audio processing. DirAC analyzes in short time windows the sound spectrum together with direction and diffuseness in frequency bands of human hearing, and uses this information in synthesis. It has applications in capturing, coding and resynthesis of spatial sound, in teleconferencing, in directional filtering, and in virtual auditory environments.

Broadband direction estimation method utilizing combined pressure and energy gradients from optimized microphone array

This paper proposes a method for analyzing the direction of the arrival of sound by estimating the sound intensity vector from the pressure and energy gradients of closely-spaced omnidirectional microphones depending on frequency. Microphones with relatively large housing, which cause shadowing, are used here to provide inter-microphone level differences in order to compute the energy gradients at high frequencies. The proposed method is evaluated in the direction analysis of a spatial-sound processing technique, Directional Audio Coding (DirAC). It is shown that the method provides a reliable direction estimation at the entire audio frequency range, whereas the traditional method employing the pressure gradients produces correct estimation in a limited frequency window only.