v7.0, 20040922, me
Friday, October 29, 1:30 pm 3:30 pm
Session Z3 Posters: LOUDSPEAKERS, Part 1
NOTE: During the first 10 minutes of the session all authors will present a brief outline of their presentation.
Z3-1 Acoustic Response Simulation of a Cone-Type Loudspeaker by the Finite Element MethodNoboru Kyouno, Kumamoto University, Kumamoto, Japan; Tsuyoshi Usagawa, Kumamoto University, Kumamoto, Japan; Tatsuo Yamabuchi, Toyama University, Toyama, Japan; Yukio Kagawa, Akita Prefectural University, Akita, Japan
Acoustic responses of an axisymmetric cone-type loudspeaker mounted in an infinite baffle have been analyzed as an electro-mechano-acoustic transducer by applying the Finite Element Method; conical shell elements to the mechanical system and triangular ring elements to the acoustic system. The outer semi-infinite space where sound is emitted from the cone speaker is treated analytically by applying the Greens function. The mechano-acoustic system of the cone speaker is connected to the electrical system by an electro-mechanical equivalent circuit. The calculated sound pressure responses are compared with measured results, demonstrating that the calculated responses are very good predictors of measured results.
Convention Paper 6242
Z3-2 Nonlinearities CharacterizationDelphine Bard, Swiss Federal Institute of Technology, Lausanne, Switzerland
This paper presents transducer nonlinearity analysis in view of compensation of these effects. We describe an experimental method of weak nonlinearity characterization, based on a representation of the nonlinearity by Volterra series and using multitone excitations. Device linearization can be achieved by applying the inverse nonlinearity upstream of the device, on the condition that the nonlinearity law is known. To address the need to distinguish nonlinear effects from linear distortions, an ad hoc experimental method has been developed. The characterization of a weakly nonlinear electroacoustic device with usual methods of measurement (THD, intermodulation) does not illustrate the nonlinearities themselves, but only some of their effects. This is the reason why this characterization method was developed.
Convention Paper 6243
Z3-3 Numerical Analysis of Total Harmonic Distortion of a Loudspeaker in a Low-Frequency RangeF. D. Zong, Z. L. Zhang, ZheJiang Normal University, ZheJiang, China
Japanese expert Yoshinisa studied the total harmonic distortion in nonlinear phenomena of the loudspeaker in a low frequency range caused by nonlinear mechanic resilience, but he ignored the case of nonlinearity of mechanic resilience and magnetic field. The authors work focuses on finding the total harmonic distortion of the nonlinear motion of the loudspeaker by means of numerical calculation. They obtained the numerical solution through numerical calculation using MATLAB software, and the corresponding curves about the total harmonic distortion versus frequency through spectrum analysis using SPECTRA PLUS software. They also analyzed the influence of nonlinearity of magnetic field on the total harmonic distortion of the loudspeaker, and drew several useful conclusions.
Convention Paper 6244
Z3-4 Characteristics of Loudspeakers by a Multilayer Piezoelectric CeramicJun Fujii, Juro Ohga, Norikazu Sasida, Shibaura Institute of Technology, Tokyo, Japan
This paper presents the construction and characteristics of a small size loudspeaker with a multilayer piezoelectric ceramic bimorph diaphragm for use with mobile telephones. The multilayer ceramic wafer is characterized by lower operation voltage due to larger capacitance than that of conventional ceramics. This is suitable for mobile equipment with battery operation. Precise measurement of diaphragm parameters and analysis of loudspeaker response are also described in this paper.
Convention Paper 6245
Z3-5 Radiation of Enclosed Loudspeaker in Baffle: Simulation Model and ResultsElena Prokofieva, Linn Products, Glasgow, Scotland, UK
A theoretical investigation of the conventional speaker, placed into a rigid wall, was presented at AES 116th Convention, Berlin, Germany (Convention Paper # 6154). The quasi-dynamic approach to the loading force and pressure was introduced there. The speaker diaphragm was regarded as a number of concentric rings. The acoustic pressure and surface velocity is predicted using the first two approximations in that paper. These simulations show the difference between the real measurements and the analytical models, used with some standard assumptions from the classic theory of plates. The results suggest that the modeling process needs to become more specified. Hence, to simulate the behavior of a standard suspension, the outer, clamped ring was given the characteristics of rubber with nonlinear deformations. The 4th approximation of the problem is formulated in this paper.
Convention Paper 6246
Z3-6 Jump Resonance in Audio TransducersAli Jabbari, Andy Unruh, Tymphany Corporation, Cupertino, CA, USA
The resonance behavior of a driver with low damping is studied. In such a system, the existing nonlinearities can result in jump resonance, a bifurcation phenomenon with two regimes. One regime, accompanied by a sudden decrease in amplitude, is evident when the frequency of excitation is increasing. The other regime, exhibiting a sudden increase in amplitude, is present when the frequency of excitation is decreasing. Jump resonance was experimentally observed in an audio transducer with low damping and subsequently confirmed by analysis and simulation using a detailed dynamic model that includes the most significant sources of nonlinearities. The conclusion of this paper is that the primary cause of jump resonance in audio transducers is the nonlinearity in the driver compliance. The importance of this phenomenon increases as the use of current amplifiers becomes more widespread, since the resulting low system damping makes jump resonance more likely.
Convention Paper 6247