While there are many topologies for implementing a graphical equalizer, this research explores a design and implementation that is based on time-varying infinite impulse response (IIR) filters. Filter blocks are obtained by interpolating between two time-invariant biquadratic filters having the same center frequency but possibly different gains and bandwidths. This corresponds to crossfading, which avoids transients during transitions. This design is suitable for digital implementation because the variable parameters are excluded from the feedback loops thus avoiding problems of stability during transitions. Moreover, the gain and the bandwidth of the band filters are jointly optimized to minimize interband interferences. Group delays are smaller than multirate or FIR implementations.
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Human beings create an internal picture of the external work by combining the information in all their sense. For example, an image can influence the localization of a virtual sound source, called the “image proximity effect.” And, similarly, the visual presentation of someone talking can strongly influence the perception of phonemes, called the “ventriloquism effect.” This paper focuses on two other aspects related to the multimodal effect: the influence of the screen size on the observed shift of the virtual sound source, and the relationship between the observed image proximity effect and the stereoscopic depth of a 3-D object. Experimental results showed that the visual angle of the presented object determines the image proximity effect regardless of the screen size.
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When a loudspeaker of a mobile device is used in a public space, the side effects are the lack of personal privacy and annoying other people. There is, therefore, a need to reduce radiated power while preserving the sound pressure at the listener’s ears. Superdirective beamforming is one approach. A finite-element (FE) model of the two-source line array positioned on the mobile phone-sized baffle is defined and then used to investigate the effect of a finite-sized baffle on the directional pattern of the piston sources. Based on these results, a two-source personal audio system was implemented in real-time, and the results validated the predictions of the FE model. At frequencies where accurate transfer response measurements are achievable, the personal audio system performs as predicted by offline simulations.
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With a digital audio workstation, in contrast to the traditional mouse-keyboard computer interface, hand gestures can be used to mix audio with eyes closed. Mixing with a visual representation of audio parameters during experiments led to broadening the panorama and a more intensive use of shelving equalizers. Listening tests proved that the use of hand gestures produces mixes that are aesthetically as good as those obtained using a mouse, keyboard, and MIDI controller. The human and artistic factor is an essential part of the art, which includes the way in which sound tools are controlled. Alternative means of control are part of sound art.
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In recent years, audio researchers in China have been devoting significant resources to the study of head-related transfer functions (HRTFs) and virtual auditory displays (VADs) in such applications as acoustics, computer games, signal processing, hearing aids, spatial sound reproductions, and many others. With financial support from the National Nature Science Fund of China, South China University of Technology and the Beijing University of Posts and Telecommunications have launched a long-term research project on HRTFs and VADs. This engineering report presents highlights of these research projects, including studies on HRTF measurements and database construction, statistical analysis on measured HRTFs, a dynamic VAD system, and an algorithm for reducing timbre coloration on virtual surround sound reproduction.
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Cinema sound is moving into an age of immersive formats with numerous channels and multiple layers. We investigate the challenges for the audio industry, some questions about object-based sound representation, and moves toward new standards.
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