Journal of the Audio Engineering Society

2006 October - Volume 54 Number 10


[Tutorial] The relationship between nonlinear distortion measurements and nonlinearities is addressed— the physical causes for signal distortion in loudspeakers, headphones, microspeakers, and other transducers. Using simulation techniques characteristic symptoms are identified for each nonlinearity and presented systematically in a guide for loudspeaker diagnostics. This information is important for understanding the implications of nonlinear parameters and for performing measurements that describe the loudspeaker more comprehensively. Practical applications of the new technique are demonstrated on three different loudspeakers.

Efficient Resonant Loudspeakers with Large Form-Factor Design Freedom

Authors: Aarts, Ronald M.; Nieuwendijk, Joris A.; Ouweltjes, Okke

Small cabinet loudspeakers with a flat response are quite inefficient. Assuming that the frequency response can be manipulated electronically, systems that have a nonflat soundpressure level (SPL) response can provide greater usable efficiency. Such a nonflat design can deal with very compact housing, but for small drivers it would require a relatively large cone excursion to obtain a high SPL. A new solution is presented that uses a resonant combination of a coupling volume and a long pipe-shaped port. In this structure the efficient resonant coupling of the driver to the acoustic load enables small drivers with modest cone displacement to achieve a high SPL. Due to the high and narrow peak in the frequency response, the normal operating range of the driver decreases considerably. This makes the driver unsuitable for normal use. To overcome this, a second measure is applied. Nonlinear processing essentially compresses the bandwidth of a 20–120-Hz 2.5-octave bass signal down to a much narrower span, which is centered where the driver efficiency is maximum. This system allows very compact loudspeakers. An experimental example of such a design is described, and a working prototype is discussed. The new loudspeaker is compared with a closed cabinet and a bass-reflex cabinet using the same drivers. It appears that the new loudspeaker has the highest output in its working range.

Vibrotactile Enhancement of Auditory-Induced Self-Motion and Spatial Presence

Authors: Väljamäe, Aleksander; Larsson, Pontus; Västfjäll, Daniel; Kleiner, Mendel

The entertainment industry frequently uses vibroacoustic stimulation, where chairs with embedded loudspeakers and shakers enhance the experience. Scientific investigations of the effect of such enhancers on illusory self-motion (vection) and spatial presence are largely missing. The current study examined whether auditory-induced vection (AIV) may be further augmented by the simultaneous presentation of additional vibrotactile cues delivered via mechanical shakers and low-frequency sound. It was found that mechanically induced vibrations increase AIV and spatial presence responses significantly. This cross-modal enhancement was stronger for stimuli containing an auditory–tactile simulation of a vehicle engine, demonstrating the benefits of the multisensory representation of virtual environments.

Virtual Air Guitar

Authors: Karjalainen, Matti; Mäki-patola, Teemu; Kanerva, Aki; Huovilainen, Antti

[Engineering Report] A combination of handheld controllers and a guitar synthesizer is called “virtual air guitar” (VAG). The name refers to playing an “air” guitar, that is, just acting the playing with music playback, and the term virtual refers to making a playable synthetic instrument. Sensing of the left-to-right-hand distance is used for pitch control, the right-hand movements are used for plucking, and in advanced versions of the VAG the finger positions of both hands can be used for other features of sound production. Three different hand gesture controllers are discussed. The sound synthesis algorithm simulates the electric guitar, augmented with sound effects such as tube amplifier distortion, as well as intelligent mapping from playing gestures to synthesis parameters. The realization of the virtual instrument is described, and sound demonstrations are available on a Web site.

[Feature Article] At the AES 120th Convention earlier this year in Paris, Jyri Huopaniemi of Nokia chaired a workshop on the important topic of binaural technology for mobile applications. Mobile applications refers to any audio technology that embraces the idea of mobility, such as handheld devices, museum guides, telephones, and the like. The aim of such applications—in areas such as enhancing user interfaces, gaming and entertainment, communication, personal content, and virtual reality—is to enhance the immersive experience of the user. A new mobile Java standard that supports 3-D audio had recently been released. This includes elements related to source properties, room properties, and listener properties, all of which were discussed by the panelists, who provided a balance between scientific and commercial perspectives.

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