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Proceedings of ACTIVE 2002, The 2002 International Symposium on Active Control of Sound and Vibration
No full textAn exploratory study into perception of acoustic speech cues by hearing-impaired adults
No full textThe aims of the present study were to assess discrimination and identification based on two classes of acoustic cue by adults with acquired sensorineural hearing impairment. Eight hearing-impaired and eight normally hearing adults were asked to identify and discriminate two different sets of speech stimuli. A plosive voicing continuum (coat/goat) varied in voice onset time. The plosive place of articulation continuum (date/gate) varied in burst spectra and second formant transition. Subjects were tested in the unaided condition with the exception of one hearing-impaired subject for whom speech was completely inaudible without a hearing aid. There was no significant between-group difference in discrimination or identification of the voicing contrast. There was no significant between-group difference in identification of stimuli varying by place of articulation. However, three of the eight hearing-impaired subjects were very poor at identification. The hearing-impaired subjects also showed significantly impaired place of articulation discrimination. Both measures were significantly correlated with threshold at 2000 Hz. The results support the view that hearing impairment can have different effects on perception of different acoustic contrasts and on different psychophysical tasks
Frequency-domain adaptation of causal digital filters
No full textThe adaptation of causal FIR digital filters in the discrete frequency domain is considered, and it is shown how the bin-normalized form of the LMS algorithm can converge to a biased solution for problems such as linear prediction. A discrete frequency-domain version of Newton's algorithm is derived, and it is demonstrated how this can converge to the optimal causal solution, even for linear prediction problems. The algorithm employs a spectral factorization of the estimated power spectral density of the reference signal, the entirely noncausal part of which is used before the causality constraint in the adaptation algorithm, and the entirely causal part is applied after the causality constraint. The spectral factors can be calculated online from a recursive estimate of the power spectral density without too great a loss of convergence speed. The extension of the algorithm to the adaptation of feedforward controllers is also described, in which case, the spectral factors of the reference signals filtered by the plant response are required, and these are shown to be equal to the spectral factors of the reference signal multiplied by the minimum phase part or the plant frequency response
Zones of quiet in a broadband diffuse sound field
No full textThe zones of quiet in pure-tone diffuse sound fields have been studied extensively in the past, both theoretically and experimentally, with the well-known result of the 10-dB attenuation extending to about a tenth of a wavelength. Recent results on the spatial-temporal correlation of broadband diffuse sound fields are used in this study to develop a theoretical framework for predicting the extension of the zones of quiet in broadband diffuse sound fields. This can be used to study the acoustic limitations imposed on local active sound control systems such as an active headrest when controlling broadband noise. Spatial-temporal correlation is first revised, after which derivations of the diffuse field zones of quiet in the near-field and the far-field of the secondary source are presented. The theoretical analysis is supported by simulation examples comparing the zones of quiet for diffuse fields excited by tonal and broadband signals. It is shown that as a first approximation the zone of quiet of a low-pass filtered noise is comparable to that of a pure-tone with a frequency equal to the center frequency of the broadband noise bandwidth
Optimisation of FTSE 100 tracker funds: a comparison of genetic algorithms and quadratic programming
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Variance of sweet spot size with head location for virtual audio
No full text3D audio systems are effective when the listener's head location is close to the head location assumed when the system was designed. In order to accommodate head movement, it is possible to design 3D sound systems that continuously select appropriate virtual audio filters that correspond to a listener's varying head position. The required spatial resolution of the audio filters depends on the size of the sweet spot. Here the size of the sweet spot of a two speaker 3D audio system is evaluated subjectively at symmetric and asymmetric head locations
Sound-field analysis by plane-wave decomposition using spherical microphone array
No full textDirectional sound-field information is becoming more important in sound-field analysis and auditorium acoustics, and, as a consequence, a variety of microphone arrays have recently been studied that provide such information. In particular, spherical microphone arrays have been proposed that provide three-dimensional information by decomposing the sound field into spherical harmonics. The theoretical formulation of the plane-wave decomposition and array performance analysis were also presented. In this paper, as a direct continuation of the recent work, a spherical microphone array configured around a rigid sphere is designed, analyzed using simulation, and then used experimentally to decompose the sound field in an anechoic chamber and an auditorium into waves. The array employs a maximum of 98 measurement positions around the sphere, and is used to compute spherical harmonics up to order 6. In the current paper we investigate the factors affecting the performance of plane-wave decomposition, showing that the direct sound and several reflections in an auditorium can be identified experimentally. This suggests that the microphone arrays studied here can be employed in various acoustic applications to identify the characteristics of reverberant sound fields
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