AES New York 2013
Paper Session P1

Thursday, October 17, 9:00 am — 11:00 am (Room 1E07)

Paper Session: P1 - Transducers—Part 1: Microphones

Helmut Wittek, SCHOEPS GmbH - Karlsruhe, Germany

P1-1 Portable Spherical Microphone for Super Hi-Vision 22.2 Multichannel AudioKazuho Ono, NHK Engineering System, Inc. - Setagaya-ku, Tokyo, Japan; Toshiyuki Nishiguchi, NHK Science & Technology Research Laboratories - Setagaya, Tokyo, Japan; Kentaro Matsui, NHK Science & Technology Research Laboratories - Setagaya, Tokyo, Japan; Kimio Hamasaki, NHK Science & Technology Research Laboratories - Setagaya, Tokyo, Japan
NHK has been developing a portable microphone for the simultaneous recording of 22.2ch multichannel audio. The microphone is 45 cm in diameter and has acoustic baffles that partition the sphere into angular segments, in each of which an omnidirectional microphone element is mounted. Owing to the effect of the baffles, each segment works as a narrow angle directivity and a constant beam width in higher frequencies above 6 kHz. The directivity becomes wider as frequency decreases and that it becomes almost omnidirectional below 500 Hz. The authors also developed a signal processing method that improves the directivity below 800 Hz.
Convention Paper 8922 (Purchase now)

P1-2 Sound Field Visualization Using Optical Wave Microphone Coupled with Computerized TomographyToshiyuki Nakamiya, Tokai University - Kumamoto, Japan; Fumiaki Mitsugi, Kumamoto University - Kumamoto, Japan; Yoichiro Iwasaki, Tokai University - Kumamoto, Japan; Tomoaki Ikegami, Kumamoto University - Kumamoto, Japan; Ryoichi Tsuda, Tokai University - Kumamoto, Japan; Yoshito Sonoda, Tokai University - Kumamoto, Kumamoto, Japan
The novel method, which we call the “Optical Wave Microphone (OWM)” technique, is based on a Fraunhofer diffraction effect between a sound wave and a laser beam. The light diffraction technique is an effective sensing method to detect the sound and is flexible for practical uses as it involves only a simple optical lens system. OWM is also very useful to detect the sound wave without disturbing the sound field. This new method can realize high accuracy measurement of slight density change of atmosphere. Moreover, OWM can be used for sound field visualization by computerized tomography (CT) because the ultra-small modulation by the sound field is integrated along the laser beam path.
Convention Paper 8923 (Purchase now)

P1-3 Proposal of Optical Wave Microphone and Physical Mechanism of Sound DetectionYoshito Sonoda, Tokai University - Kumamoto, Kumamoto, Japan; Toshiyuki Nakamiya, Tokai University - Kumamoto, Japan
An optical wave microphone with no diaphragm, which uses wave optics and a laser beam to detect sounds, can measure sounds without disturbing the sound field. The theoretical equation for this measurement can be derived from the optical diffraction integration equation coupled to the optical phase modulation theory, but the physical interpretation or meaning of this phenomenon is not clear from the mathematical calculation process alone. In this paper the physical meaning in relation to wave-optical processes is considered. Furthermore, the spatial sampling theorem is applied to the interaction between a laser beam with a small radius and a sound wave with a long wavelength, showing that the wavenumber resolution is lost in this case, and the spatial position of the maximum intensity peak of the optical diffraction pattern generated by a sound wave is independent of the sound frequency. This property can be used to detect complex tones composed of different frequencies with a single photo-detector. Finally, the method is compared with the conventional Raman-Nath diffraction phenomena relating to ultrasonic waves. AES 135th Convention Best Peer-Reviewed Paper Award Cowinner
Convention Paper 8924 (Purchase now)

P1-4 Numerical Simulation of Microphone Wind Noise, Part 2: Internal FlowJuha Backman, Nokia Corporation - Espoo, Finland
This paper discusses the use of the computational fluid dynamics (CFD) for computational analysis of microphone wind noise. The previous part of this work showed that an external flow produces a pressure difference on the external boundary, and this pressure causes flow in the microphone internal structures, mainly between the protective grid and the diaphragm. The examples presented in this work describe the effect of microphone grille structure and microphone diaphragm properties on the wind noise sensitivity related to the behavior of this kind of internal flows.
Convention Paper 8925 (Purchase now)

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