A method for spectral and spatial multichannel analysis/synthesis of interior aircraft sounds is presented. We propose two extensions of the classical sinusoids+noise model, adapted to multichannel stationary sounds. First, a spectral estimator is described, using average information across channels for spectral peak detection. Second, the residual modeling is extended to integrate two interchannel spatial cues (i.e., coherence and phase difference). This approach allows real-time synthesis and control of sounds spectral and spatial characteristics. It finds applications for multichannel aircraft sound reproduction, and more generally for musical and environmental sound synthesis. The ability of the model to reproduce multichannel aircraft sounds is assessed by a numerical simulation.

The inverse fast Fourier transform (IFFT) method is a time-frequency technique which was proposed to alleviate the complexity of the additive sound synthesis method in real-time applications. However, its application is limited by its inherent tradeoff between time and frequency resolutions, which are determined by the number of frequencies used for time-frequency processing. In a previous work, the authors proposed a frequency-refining technique for overcoming this frequency limitation, permitting achieving any time and frequency resolution using a small number of frequencies. In this correspondence we extend this work, by proposing a time-refining technique which permits overcoming the time resolution limitation for a given number of frequencies. Additionally, we propose an alternative to the frequency-refining technique proposed in our previous work, which requires about half the computations. The combination of these two results permits achieving any time and frequency resolution for any given number of frequencies. Using this property, we find the number of frequencies which minimizes the overall complexity. We do so considering two different application scenarios (i.e., offline sound design and online real-time synthesis). This results in a major complexity reduction in comparison with the design proposed in our previous work.

The inverse fast Fourier transform (FFT) method was proposed to alleviate the computational complexity of the additive sound synthesis method in real-time applications, and consists in synthesizing overlapping blocks of samples in the frequency domain. However, its application is limited by its inherent tradeoff between time and frequency resolution. In this paper, we propose an alternative to the inverse FFT method for synthesizing colored noise. The proposed approach uses subband signal processing to generate time-frequency noise with an autocorrelation function such that the noise obtained after converting it to time domain has the desired power spectral density. We show that the inverse FFT method can be interpreted as a particular case of the proposed method, and therefore, the latter offers some extra design flexibility. Exploiting this property, we present experimental results showing that the proposed method can offer a better tradeoff between time and frequency resolution, at the expense of some extra computations.

Nowadays, interactive 3-D environments tend to include both synthesis and spatialization processes to increase the realism of virtual scenes. In typical systems, audio generation is created in two stages: first, a monophonic sound is synthesized (generation of the intrinsic timbre properties) and then it is spatialized (positioned in its environment). In this paper, we present the design of a 3-D immersive synthesizer dedicated to environmental sounds, and intended to be used in the framework of interactive virtual reality applications. The system is based on a physical categorization of environmental sounds (vibrating solids, liquids, aerodynamics). The synthesis engine has a novel architecture combining an additive synthesis model and 3-D audio modules at the prime level of sound generation. An original approach exploiting the synthesis capabilities for simulating the spatial extension of sound sources is also presented. The subjective results, evaluated with a formal listening test, are discussed. Finally, new control strategies based on a global manipulation of timbre and spatial attributes of sound sources are introduced.