| President's Message (PDF-81KB) Neil Gilchrist | 1003 |
| PAPERS | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| STANDARDS AND INFORMATION DOCUMENTS | |
| 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 | |
| FEATURES | |
| Loudspeaker Array Technology (PDF-378KB) | 1081 |
| 28th Conference, Piteå, Call for Papers (PDF-73KB) | 1104 |
| DEPARTMENTS | |
| 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 |
| EXTRAS | |
| Cover & Sustaining Members List (PDF-314KB) | |
| AES Officers, Committees, Offices & Journal Staff (PDF-104KB) | |
