Last Updated: 20050816, mei
P18 - Microphones & Internet Audio
Monday, October 10, 10:00 am — 12:00 pm
Chair: Eddy B. Brixen, DPA Microphones A/S - Allerød, Denmark; and EBB-consult, Smørum, Denmark
P18-1 The Native B-Format Microphone: Part 1—Eric Benjamin, Thomas Chen, Dolby Laboratories - San Francisco, CA, USA
Ambisonic sound recording is predicated on the acquisition of audio signals in what has been termed “B-format,” which is the output of a microphone array known as the Soundfield Microphone. That microphone is a tetrahedral array of nominally cardioid microphone capsules. The capsule signals are processed in such a way as to give four output signals that are proportional to the pressure and the three-dimensional particle velocity vector at the center of the array. These same signals can be achieved by the use of a single omnidirectional microphone and three figure-of-eight microphones located close to each other. Errors in the shape of the polar pattern or in the ratio of the direct to diffuse-field sensitivity of the microphones result. The two methods are compared in both a theoretical analysis and in acoustical measurements. The results of the comparison of experimental recordings using these two types of arrays will be presented in part two of this paper.
Convention Paper 6621 (Purchase now)
P18-2 A Web Search Engine for Sound Effects—Stephen V. Rice, University of Mississippi - University, MS, USA; Stephen M. Bailey, Comparisonics Corporation - Grass Valley, CA, USA
FindSounds is the first Web search engine for sound effects. Queries are processed using a selective index of Web audio files that includes sound effects and musical instrument samples but excludes song and speech recordings. A text search retrieves audio files based on how they are labeled, and a “sounds-like” search locates audio files based on sound similarity. Each month FindSounds processes more than 1.5 million queries for more than 150,000 Internet users.
Convention Paper 6622 (Purchase now)
P18-3 Alternative Approaches for Recording Surround Sound—Colin Preston, South East Essex College - Southend-on-Sea, Essex, UK
The aim of this paper is to describe a series of adaptations of stereo microphone techniques for surround sound. The adaptations provide variable microphone polar patterns, multiple outputs for surround sound, as well as retaining a conventional 2-channel stereo output. The system enables the recording engineer to position and adjust the microphone cluster for a conventional stereo output and then derive the surround sound outputs. It is also possible to record the microphone outputs separately and create the desired polar patterns in postproduction. The technique also has creative applications for multimicrophone or multitrack situations where a number of single microphones would be used.
Convention Paper 6623 (Purchase now)
P18-4 Microphones, High Wind, and Rain—Eddy B. Brixen, DPA Microphones A/S - Allerød, Denmark; and EBB-consult, Smørum, Denmark
In outdoor recording, high wind and rain are generally a problem as this causes unwanted noise in the microphone signal. In order to prevent noise, the microphones can be protected from the weather by using windjammers, windscreens, etc. However, the effectiveness of these products varies significantly and full specifications characterizing maximum wind speed permitted, wind attenuation, spectral damping, influence by rain, etc., are seldom given. In this paper an overview of the problems involved in the specification of microphone systems for outdoor recording is given. It proposes measurements and a form of presentation that might provide more informative specifications.
Convention Paper 6624 (Purchase now)