AES Journal

Journal of the AES

2005 November - Volume 53 Number 11


President's Message (PDF-81KB)                            Neil Gilchrist    1003
Three-Dimensional Surround Sound Systems Based on Spherical Harmonics (PDF-713KB)  
M. A. Poletti    1004
Based on spherical harmonics, this paper reviews and extends the three-dimensional theory of sound recording and reproduction. Three methods of recording are compared: free-space directional microphone arrays, pressure microphones mounted in a sphere, and free-space arrays with variable radii. An analysis shows that appropriate sound fields can be created without the requirement of dipole loudspeakers. In addition, mode matching can be extended to reverberant environments with nonideal loudspeakers.  

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High-Order Digital Parametric Equalizer Design (PDF-708KB)  
Sophocles J. Orfanidis    1026
Unlike classical equalizers having first- or second-order filters, using higher order Butterworth, Chebyshev, and elliptic analog prototypes provides flatter passbands and sharper band edges. The analysis shows their advantages. Equalizer coefficients are computed using center frequency, peak gain, bandwidth, and bandwidth gain. The discussions on topology explore transposed, normalized-lattice, and minimum roundoff noise state-space realizations. Design methods apply equally well to low-pass and high-pass shelving filters and to ordinary bandpass and bandstop filters.  

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Stability and Sensitivity Analyses for Diffusers with Single and Multiple Active Elements (PDF-402KB)  
Mark R. Avis, Lejun Xiao, and Trevor J. Cox    1047
Passive diffusers are used to improve spatial acoustics, but they are limited to mid and high frequencies because of the required depth. Alternatively, by actively controlling the surface impedance with an electronic control system, reflected wave fronts can be dispersed. While active impedance technology has been used usually to absorb sound and cancel noise, it can also be used for sound dispersion. Active diffusers are more difficult to use than active absorbers because of tighter requirements on system accuracy. Test results confirm that the stability of a real system is consistent with the theoretical analysis and that active diffusers are prone to instability.  

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Acoustic Analysis and Design of Miniature Loudspeakers for Mobile Phones (PDF-641KB)  
Mingsian R. Bai and Jerwoei Liao    1061
Increasing needs for audio quality in miniature loudspeakers used in mobile phones requires tradeoffs not found in conventional large loudspeakers. Miniature loudspeakers have a smaller Bl product, which influences the high-frequency rolloff and sensitivity. An electroacoustic analysis explores a model of the duct structure and head diffraction effects. An acoustic design to extend the low-frequency bandwidth is suggested to increase perceived quality. Large-signal performance appears to be a critical issue.  

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AES Standards Committee News (PDF-97KB)    1078
Recoding data set for audio bit-rate reduction; digital input/output interfacing; audio connectors; grounding and EMC; storage and handling of media  
Loudspeaker Array Technology (PDF-378KB)    1081
28th Conference, Pite��, Call for Papers (PDF-73KB)    1104
News of the Sections (PDF-800KB)    1085
Sound Track (PDF-83KB)    1092
Upcoming Meetings (PDF-83KB)    1092
New Products and Developments (PDF-83KB)    1092
Available Literature (PDF-79KB)    1094
Membership Information (PDF-172KB)    1095
Advertiser Internet Directory (PDF-181KB)    1099
In Memoriam (PDF-181KB)    1102
AES Annual Report (PDF-72KB)    1103
Sections Contacts Directory (PDF-121KB)    1105
AES Conventions and Conferences (PDF-254KB)    1112
Cover & Sustaining Members List (PDF-314KB)    
AES Officers, Committees, Offices & Journal Staff (PDF-104KB)    

Supplementary Material

AES - Audio Engineering Society