AES 東京コンベンション 2009
Paper Session A2

The mechanical vibration of loudspeaker drive units is described by a set of linear transfer functions and geometrical data which are measured at selected points on the surface of the radiator by using a scanning technique. The mechanical vibration can be summarized to a new quantity called accumulated acceleration level (AAL) which is comparable with the sound pressure level (SPL) if no acoustical cancellation occurs. These derived parameters are the basis for modal analysis and make the relationship between mechanical vibration and sound pressure output more transparent. Finally, the usage of the distributed parameters within finite and boundary element analyses is addressed and conclusions for the loudspeaker design process are made.

This paper describes the development of a super-wide-range microphone with cardioid directivity, which covers the frequency range up to 100 kHz. The proposed microphone adopted a two capsule configuration composed of an omnidirectional capsule covering up to 100 kHz and a bidirectional capsule designed to fit the characteristics of the omnidirectional one. The bidirectional capsule was designed to precisely fit the sensitivity level and the intrinsic noise level of the omnidirectional capsule . The measurement results show that the proposed microphone achieves wide frequency range up to 100 kHz, as well as low noise characteristics and excellent cardioid directivity.

Novel microphone structure to enable rear sensitivity to be significantly suppressed is proposed. It improves open-air recording quality by comprising a line microphone capsule and a second order pressure gradient directional microphone. We made two types of prototype microphones whose length are 29 cm and 15 cm. They successfully suppress their rear sensitivity by more than 10 dB compared to conventional line microphones in the frequency range in which major outdoor noise often occurs. Its additional advantage is that they don't need a complicated signal processing circuit and availability of a normal 48 V phantom power supply. This paper describes the fundamental principle of the microphone's rear sensitivity suppression and the measurement results of their acoustic characteristics.

NHK began to use the newly-developed narrow-angle directional microphones with suppressed rear sensitivity which were developed for the outside broadcasting. The microphones have a narrow directivity specializing in the front sensitivity. We have tested these microphones in the several TV programs, and discussed their characteristics and practicability. In this paper, we will report an obtained new method of positioning the microphones to pick up objective sounds in a noisy field, comparing with the common one.