AES San Francisco 2012
Paper Session P5

P5 - Measurement and Models

Friday, October 26, 2:00 pm — 6:00 pm (Room 121)

Louis Fielder, Dolby - San Francisco, CA, USA

P5-1 Measurement of Harmonic Distortion Audibility Using a Simplified Psychoacoustic ModelSteve Temme, Listen, Inc. - Boston, MA, USA; Pascal Brunet, Listen, Inc. - Boston, MA, USA; Parastoo Qarabaqi, Listen, Inc. - Boston, MA, USA
A perceptual method is proposed for measuring harmonic distortion audibility. This method is similar to the CLEAR (Cepstral Loudness Enhanced Algorithm for Rub & buzz) algorithm previously proposed by the authors as a means of detecting audible Rub & Buzz, which is an extreme type of distortion [1,2]. Both methods are based on the Perceptual Evaluation of Audio Quality (PEAQ) standard [3]. In the present work, in order to estimate the audibility of regular harmonic distortion, additional psychoacoustic variables are added to the CLEAR algorithm. These variables are then combined using an artificial neural network approach to derive a metric that is indicative of the overall audible harmonic distortion. Experimental results on headphones are presented to justify the accuracy of the model.
Convention Paper 8704 (Purchase now)

P5-2 Overview and Comparison of and Guide to Audio Measurement MethodsGregor Schmidle, NTi Audio AG - Schaan, Liechtenstein; Danilo Zanatta, NTi Audio AG - Schaan, Liechtenstein
Modern audio analyzers offer a large number of measurement functions using various measurement methods. This paper categorizes measurement methods from several perspectives. The underlying signal processing concepts, as well as strengths and weaknesses of the most popular methods are listed and assessed for various aspects. The reader is offered guidance for choosing the optimal measurement method based on the specific requirements and application.
Convention Paper 8705 (Purchase now)

P5-3 Spherical Sound Source for Acoustic MeasurementsPlamen Valtchev, Univox - Sofia, Bulgaria; Dimitar Dimitrov, BMS Production; Rumen Artarski, Thrax - Sofia, Bulgaria
A spherical sound source for acoustic measurements is proposed, consisting of a pair of coaxial loudspeakers and a pair of compression drivers radiating into a common radially expanding horn in full 360-degree horizontal plane. This horn’s vertical radiation pattern is defined by the enclosures of the LF arrangement. The LF membranes radiate spherically the 50 to 500 Hz band, whereas their HF components complete the horizontal horn reference ellipsoid-like diagram in both vertical directions to a spherical one. The assembly has axial symmetry, thus perfect horizontal polar pattern. The vertical pattern is well within ISO 3382 specifications, even without any “gliding.” Comparative measurements against a purposely built typical dodecahedron revealed superior directivity, sound power capability, and distortion performance.
Convention Paper 8706 (Purchase now)

P5-4 Low Frequency Noise Reduction by Synchronous Averaging under Asynchronous Measurement System in Real Sound FieldTakuma Suzuki, Etani Electronics Co., Ltd. - Ohta-ku, Tokyo, Japan; Hiroshi Koide, Etani Electronics Co., Ltd. - Ohta-ku, Tokyo, Japan; Akihiko Shoji, Etani Electronics Co., Ltd. - Ohta-ku, Tokyo, Japan; Kouichi Tsuchiya, Etani Electronics Co., Ltd. - Ohta-ku, Tokyo, Japan; Tomohiko Endo, Etani Electronics Co., Ltd. - Ohta-ku, Tokyo, Japan; Shokichiro Hino, Etani Electronics Co. Ltd - Ohta-ku, Tokyo, Japan
An important feature in synchronous averaging is the synchronization of sampling clock between the transmitting and receiving devices (e.g., D/A and A/D converters). However, in the case where the devices are placed apart, synchronization becomes difficult to gain. For such circumstances, an effective method is proposed that enables synchronization for an asynchronous measurement environment. Normally, a swept-sine is employed as a measuring signal but because its power spectrum is flat, the signal-to-noise ratio (SNR) is decreased in a real environment with high levels of low frequency noise. To solve this, the devised method adopts the means of “enhancing the signal source power in low frequencies” and “placing random fluctuations in the repetitive period of signal source.” Subsequently, its practicability was verified.
Convention Paper 8707 (Purchase now)

P5-5 Measurement and Analysis of the Spectral Directivity of an Electric Guitar Amplifier: Vertical PlaneAgnieszka Roginska, New York University - New York, NY, USA; Justin Mathew, New York University - New York, NY, USA; Andrew Madden, New York University - New York, NY, USA; Jim Anderson, New York University - New York, NY, USA; Alex U. Case, fermata audio + acoustics - Portsmouth, NH, USA; University of Massachusetts—Lowell - Lowell, MA, USA
Previous work presented the radiation pattern measurement of an electric guitar amplifier densely sampled spatially on a 3-D grid. Results were presented of the directionally dependent spectral features on-axis with the driver, as a function of left/right position, and distance. This paper examines the directionally dependent features of the amplifier measured at the center of the amplifier, in relationship to the height and distance placement of the microphone. Differences between acoustically measured and estimated frequency responses are used to study the change in the acoustic field. This work results in a better understanding of the spectral directivity of the electric guitar amplifier in all three planes.
Convention Paper 8708 (Purchase now)

P5-6 The Radiation Characteristics of a Horizontally Asymmetrical Waveguide that Utilizes a Continuous Arc Diffraction SlotSoichiro Hayashi, Bose Corporation - Framingham, MA, USA; Akira Mochimaru, Bose Corporation - Framingham, MA, USA; Paul F. Fidlin, Bose Corporation - Framinham, MA, USA
One of the unique requirements for sound reinforcement speaker systems is the need for flexible coverage control—sometimes this requires an asymmetrical pattern. Vertical control can be achieved by arraying sound sources, but in the horizontal plane, a horizontally asymmetrical waveguide may be the best solution. In this paper the radiation characteristics of horizontally asymmetrical waveguides with continuous arc diffraction slots are discussed. Waveguides with several different angular variations are developed and their radiation characteristics are measured. Symmetrical and asymmetrical waveguides are compared, and the controllable frequency range and limitations are discussed.
Convention Paper 8709 (Purchase now)

P5-7 Analysis on Multiple Scattering between the Rigid-Spherical Microphone Array and Nearby Surface in Sound Field RecordingGuangzheng Yu, South China University of Technology - Guangzhou, Guangdong, China; Bo-sun Xie, South China University of Technology - Guangzhou, China; Yu Liu, South China University of Technology - Guangzhou, China
The sound field recording with a rigid spherical microphone array (RSMA) is a newly developed technique. In room sound field recording, when an RSMA is close to a reflective surface, such as the wall or floor, the multiple scattering between the RSMA and the surface occurs and accordingly causes the error in the recorded signals. Based on the mirror-image principle of acoustics, an equivalent two-sphere model is suggested, and the multipole expansion method is applied to analyze the multiple scattering between the RSMA and reflective surface. Using an RSMA with 50 microphones the relationships among the error in RSMA output signals caused by multiple scattering and frequency, direction of incident plane wave, and distance of RSMA relative to reflective surface are analyzed.
Convention Paper 8710 (Purchase now)

P5-8 Calibration of Soundfield Microphones Using the Diffuse-Field ResponseAaron Heller, SRI International - Menlo Park, CA, USA; Eric M. Benjamin, Surround Research - Pacifica, CA, USA
The soundfield microphone utilizes an array of microphones to derive various components of the sound field to be recorded or measured. Given that at high frequencies the response varies with the angle of incidence, it may be argued that any angle of incidence is as important as another, and thus it is important to achieve a calibration that achieves an optimum perceived response characteristic. Gerzon noted that “Above a limiting frequency F ˜ c/(pi r) [. . .] it is found best to equalise the nominal omni and figure-of-eight outputs for an approximately flat response to homogeneous random sound fields.” In practice, however, soundfield microphones have been calibrated to realize a flat axial response. The present work explores the theoretical ramifications of using a diffuse-field equalization target as opposed to a free-field equalization target and provides two practical examples of diffuse-field equalization of tetrahedral microphone arrays.
Convention Paper 8711 (Purchase now)

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