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Authors: Klippel, Wolfgang
Traditional modeling describes the heat flow in loudspeakers by an equivalent circuit using integrators with different time constants. The parameters of the lumped elements are assumed to be independent of the amplitude of the signal. The simple model fails in describing the forced-air convection cooling, which becomes an effective cooling mechanism if the velocity of the coil and/or the air velocity in the gap becomes high. A large-signal model which considers the nonlinear interactions between the electromechanical and the thermal mechanisms is described. The model and parameters are verified by practical measurements on the drivers. The dominant paths for the heat flow are identified, and means for increasing the power handling capacity are discussed.
Authors: González, Alberto; Zuccarello, Pedro; Piñero, Gema; de Diego, María
The time involved in measuring the linear characteristics of acoustic systems is a common problem in audio signal processing. Recent years have witnessed a major advance in multiple-channel sound reproduction systems. Using the simple idea of frequency-domain multiplexing, a technique for performing simultaneous multiple-channel impulse response measurements is proposed. A previous technique that uses time-domain multiplexing is also revisited. Several measurements are performed in order to compare the reliability of simultaneous and sequential methods. Experimental results show that both methods have similar accuracy, but the simultaneous measurement case provides measurement versatility and saves time.
Authors: Blasizzo, Fabio
The capability of a moving-coil loudspeaker to sustaining a certain power is related to its capability of dissipating heat produced by the Joule effect in the moving coil and, due to eddy currents, in the pole piece. Different heat transmission phenomena were analyzed in order to determine a lumped-element thermal model realistically related to the physics of the process. The model is based on the Zuccatti-Button approach. However, a more detailed model has been developed in order to consider all the heat transmission processes involved. In particular, forced-air convection, induced by the cone movement at low frequencies (30-150 Hz), has been taken into account.
Authors: Matsumoto, Mitsuo; Yamanaka, Susumu; Toyama, Mikio; Nomura, Hiroaki
The effect of correcting the arrival times when interpolating binaural impulse responses for a moving sound image was investigated for a linear interpolation method, a discrete Fourier transform method, and a spline method. Interpolation is required because the number of responses needed to localize a moving sound image is too great for them to be measured individually. Evaluation using the signal-to-deviation ratio showed that arrival time correction improved the interpolation accuracy with all three methods, except for responses at a few azimuths.
Authors: Rumsey, Francis
[feature] In the last few years we have witnessed a number of advanced developments in the design of listening tests. These advances represent a more sophisticated approach to sound quality evaluation than basic quality judgments and mean opinion scores. In particular, researchers have been investigating ways of discovering more precisely what listeners perceive, how they describe it, and how to predict consumer preference on the basis of expert judgment. This article introduces some of the techniques and applications discussed in papers given at recent AES conventions and conferences.
Authors: Rumsey, Francis
[feature] Recently considerable attention has been given to ways in which more sophisticated microphone arrays and panning laws can be used to derive accurate soundfield representations, phantom imaging, and source panning. There has also been an interest in ways to represent or capture a diffuse field in the 5.1 format. This article considers some recent contributions in this field, primarily those techniques that have some relevance to the ITU standard surround format (3/2 stereo or 5.1 surround). It is interesting to notice a degree of convergence between theories based on different concepts of soundfield representation and a revisiting of older theories based on Ambisonic principles. Although some of the microphone arrays described below, for example, are aimed at capturing high-order spatial representations of a soundfield, the authors show how they can be adapted to provide outputs for the 5-channel ITU standard layout. In other words, the final rendering format can be independent of the format in which the sound is captured and stored. This surely has to be the way forward as audio engineers wrestle with increasingly diverse multichannel formats with varying numbers of loudspeakers in potentially different locations.
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