Download Differentiable Active Acoustics - Optimizing Stability via Gradient Descent Active acoustics (AA) refers to an electroacoustic system that actively modifies the acoustics of a room. For common use cases, the number of transducers—loudspeakers and microphones—involved in the system is large, resulting in a large number of system parameters. To optimally blend the response of the system into the natural acoustics of the room, the parameters require careful tuning, which is a time-consuming process performed by an expert. In this paper, we present a differentiable AA framework, which allows multi-objective optimization without impairing architecture flexibility. The system is implemented in PyTorch to be easily translated into a machine-learning pipeline, thus automating the tuning process. The objective of the pipeline is to optimize the digital signal processor (DSP) component to evenly distribute the energy in the feedback loop across frequencies. We investigate the effectiveness of DSPs composed of finite impulse response filters, which are unconstrained during the optimization. We study the effect of multiple filter orders, number of transducers, and loss functions on the performance. Different loss functions behave similarly for systems with few transducers and low-order filters. Increasing the number of transducers and the order of the filters improves results and accentuates the difference in the performance of the loss functions.
Download Spherical Decomposition of Arbitrary Scattering Geometries for Virtual Acoustic Environments A method is proposed to encode the acoustic scattering of objects for virtual acoustic applications through a multiple-input and
multiple-output framework. The scattering is encoded as a matrix in the spherical harmonic domain, and can be re-used and
manipulated (rotated, scaled and translated) to synthesize various
sound scenes. The proposed method is applied and validated using
Boundary Element Method simulations which shows accurate results between references and synthesis. The method is compatible
with existing frameworks such as Ambisonics and image source
methods.
Download On studying auditory distance perception in concert halls with multichannel auralizations Virtual acoustics and auralizations have been previously used to study the perceptual properties of concert hall acoustics in a descriptive profiling framework. The results have indicated that the apparent auditory distance to the orchestra might play a crucial role in enhancing the listening experience and the appraisal of hall acoustics. However, it is unknown how the acoustics of the hall influence auditory distance perception in such large spaces. Here, we present one step towards studying auditory distance perception in concert halls with virtual acoustics. The aims of this investigation were to evaluate the feasibility of the auralizations and the system to study perceived distances as well as to obtain first evidence on the effects of hall acoustics and the source materials to distance perception. Auralizations were made from measured spatial impulse responses in two concert halls at 14 and 22 meter distances from the center of a calibrated loudspeaker orchestra on stage. Anechoic source materials included symphonic music and pink noise as well as signals produced by concatenating random segments of anechoic instrument recordings. Forty naive test subjects were blindfolded before entering the listening room, where they verbally reported distances to sound sources in the auralizations. Despite the large variance in distance judgments between the individuals, the reported distances were on average in the same range as the actual distances. The results show significant main effects of halls, distances and signals, but also some unexpected effects associated with the presentation order of the stimuli.