A novel design of two-way multimedia loudspeaker
A multimedia loudspeaker usually stands on a desk, so the reflected sound from the desk interferes with the direct sound from the loudspeaker. Reflected sound from the desk must be taken into consideration in the designing process in order to obtain the flattest possible resultant frequency response in the listening position. This paper introduces a novel design of a two-way multimedia loudspeaker, which gives flat frequency response at broad range of distances from the listener.
A High Fidelity Small-sized Loudspeaker
Although bass sound reproduction through a small-sized loudspeaker requires large diaphragm displacement, the conventional supporting system cannot vibrate at an amplitude large enough for high-quality bass sound reproduction. A new supporting system is proposed which solves the problem of the conventional supporting system and focuses on the high excursion supporting system in terms of structure and displacement mechanism, in comparison with the conventional system. Using the supporting system with improved amplitude linearity and a driving system with a high force factor, a small-sized loudspeaker 8 cm in diameter has been developed. Despite the small diameter, this loudspeaker provides a large diaphragm displacement of /spl plusmn/8 mm, and therefore has superior bass sound reproduction characteristics.
New Low-Profile Applicators for Local Heating of Tissues
A new type of low-profile applicator is described giving efficient power transfer to tissue with low leakage. It consists of a resonant element spaced from a ground plane by low-loss material having high relative permittivity and some relative permeability. This combination is covered by similar material which can be placed in direct contact with the tissue to be heated, or separated from it by a water bolus as required. Laboratory measurements using phantom materials show that these applicators are well matched and produce well defined and relatively uniform heating profiles. Applicators having maximum dimensions of 3-15 cm covering the frequency range 1000-100 MHz, respectively, are described. Penetration depths of at least 4 cm at 100-200 MHz are achieved. Tests on anesthetised pigs and some clinical assessment have confirmed the usefulness of this compact low-frequency type of applicator and have shown that performance compares favorably with that of other recently reported types. The design can be optimized for treatment of specific sites, and suitable choice of dimensions and electrical characteristics of the layer material allow the low-profile concept to be extended over a wide range of operating frequencies.