In this article a practical relationship is shown that gives the connection between the forms of the directional characteristics (cardioid, super-cardioid and hyper-cardioid) and the parameters of the microphone. An electro-dynamic microphone with two acoustical entrances is examined and placed in a field of a spherical sound wave. Shown is the relationship between space characteristics when the microphone is in sphere and planar sound wave. Shown are the basic proportion between the angles Q = 0 and Q = 180 (proportion front – back), as well as when Q = 0 and Q = 90 degrees and their relationship with the microphone parameters when the microphone is in sphere sound wave. Proven is that the form of the directional characteristics in the area of the lower frequencies are a function only of the proportion of the phase angles and the ratio between the distance of the two acoustical entrances and the distance between the microphone and the sound source.
Convention Paper 5498

09:30 h
A2 Parabolic Reflector Microphones – Juha Backman, Nokia Mobile Phones, Espoo, Finland

The paper presents a series of measurements on the behavior of parabolic reflector microphones. The measurements include gain, sound pressure distribution, and directional properties. These results indicate that although it is easy to obtain considerable high-frequency acoustical gain, the usable angle is extremely narrow, and having the source at a non-ideal position (near-field or off-axis) leads to a geometrical distortion of the focal point, reducing the high-frequency gain. The potential benefit of directional microphones and the theoretical gain properties are discussed.
Convention Paper 5499

10:00 h
A3 Microphone Techniques and Directional Quality of Sound Reproduction – Ville Pulkki, Helsinki University of Technology, Espoo, Finland

Different spatial sound reproduction techniques are evaluated using a binaural auditory model. Ear canal signals for different microphone techniques and different loudspeaker reproduction are simulated. Directional auditory cues are calculated and directional quality is discussed. The results of recording techniques for stereophonic listening explain the subjective opinions presented in literature: With coincident microphone techniques directionally fairly stable and consistent virtual sources can be produced, and with spaced microphones more spread and ambiguous virtual sources are achieved. In multichannel reproduction, none of the existing microphone techniques are found to produce good directional quality. Both coincident and spaced microphone techniques produce spread virtual sources.
Convention Paper 5500

10:30 h
A4 Applications of a 3-D Microphone Array – Juha Merimaa, Helsinki University of
Technology, Espoo, Finland

Sound field inside an enclosed space depends in a complex way upon interactions between emitted sound waves and different reflecting, diffracting, and scattering surfaces. 3-D microphone arrays provide tools for investigating and recording these interactions. This paper discusses several existing array techniques introducing a variety of application targets for the HUT microphone probe. Applications include directional measurement, analysis, and visualization of room responses, estimation of room parameters and analysis of source and surface positions. In a dynamic case the probe can be utilized in source tracking and beam steering, as well as in tracking its own position. Furthermore, the probe can be used to simulate some microphone arrays commonly used in surround sound recording. In each application case both general theory and its relation to the HUT probe is discussed.
Convention Paper 5501