AES San Francisco 2012
Paper Session P10
Saturday, October 27, 2:00 pm — 6:00 pm (Room 121)
Paper Session: P10 - Transducers
Alex Voishvillo, JBL Professional - Northridge, CA, USA
P10-1 The Relationship between Perception and Measurement of Headphone Sound Quality—Sean Olive, Harman International - Northridge, CA, USA; Todd Welti, Harman International - Northridge, CA, USA
Double-blind listening tests were performed on six popular circumaural headphones to study the relationship between their perceived sound quality and their acoustical performance. In terms of overall sound quality, the most preferred headphones were perceived to have the most neutral spectral balance with the lowest coloration. When measured on an acoustic coupler, the most preferred headphones produced the smoothest and flattest amplitude response, a response that deviates from the current IEC recommended diffuse-field calibration. The results provide further evidence that the IEC 60268-7 headphone calibration is not optimal for achieving the best sound quality.
Convention Paper 8744 (Purchase now)
P10-2 On the Study of Ionic Microphones—Hiroshi Akino, Audio-Technica Co. - Machida-shi, Tokyo, Japan; Kanagawa Institute of Technology - Kanagawa, Japan; Hirofumi Shimokawa, Kanagawa Institute of Technology - Kanagawa, Japan; Tadashi Kikutani, Audio-Technica U.S., Inc. - Stow, OH, USA; Jackie Green, Audio-Technica U.S., Inc. - Stow, OH, USA
Diaphragm-less ionic loudspeakers using both low-temperature and high-temperature plasma methods have already been studied and developed for practical use. This study examined using similar methods to create a diaphragm-less ionic microphone. Although the low-temperature method was not practical due to high noise levels in the discharges, the high-temperature method exhibited a useful shifting of the oscillation frequency. By performing FM detection on this oscillation frequency shift, audio signals were obtained. Accordingly, an ionic microphone was tested in which the frequency response level using high-temperature plasma increased as the sound wave frequency decreased. Maintaining performance proved difficult as discharges in the air led to wear of the needle electrode tip and adhesion of products of the discharge. Study results showed that the stability of the discharge corresponded to the non-uniform electric field that was dependent on the formation shape of the high-temperature plasma, the shape of the discharge electrode, and the use of inert gas that protected the needle electrode. This paper reviews the experimental outcome of the two ionic methods, and considerations given to resolve the tip and discharge product and stability problems.
Convention Paper 8745 (Purchase now)
P10-3 Midrange Resonant Scattering in Loudspeakers—Juha Backman, Nokia Corporation - Espoo, Finland
One of the significant sources of midrange coloration in loudspeakers is the resonant scattering of the exterior sound field from ports, recesses, or horns. This paper discusses the qualitative behavior of the scattered sound and introduces a computationally efficient model for such scattering, based on waveguide models for the acoustical elements (ports, etc.), and mutual radiation impedance model for their coupling to the sound field generated by the drivers. In the simplest case of driver-port interaction in a direct radiating loudspeaker an approximate analytical expression can be written for the scattered sound. These methods can be applied to numerical optimization of loudspeaker layouts.
Convention Paper 8746 (Purchase now)
P10-4 Long Distance Induction Drive Loud Hailer Characterization—Marshall Buck, Psychotechnology, Inc. - Los Angeles, CA, USA; Wisdom Audio; David Graebener, Wisdom Audio Corporation - Carson City, NV, USA; Ron Sauro, NWAA Labs, Inc. - Elma, WA, USA
Further development of the high power, high efficiency induction drive compression driver when mounted on a tight pattern horn results in a high performance loud hailer. The detailed performance is tested in an independent laboratory with unique capabilities, including indoor frequency response at a distance of 4 meters. Additional characteristics tested include maximum burst output level, polar response, and directivity balloons. Outdoor tests were also performed at distances up to 220 meters and included speech transmission index and frequency response. Plane wave tube driver-phase plug tests were performed to assess incoherence, power compression, efficiency, and frequency response.
Convention Paper 8747 (Purchase now)
P10-5 Optimal Configurations for Subwoofers in Rooms Considering Seat to Seat Variation and Low Frequency Efficiency—Todd Welti, Harman International - Northridge, CA, USA
The placement of subwoofers and listeners in small rooms and the size and shape of the room all have profound influences on the resulting low frequency response. In this study, a computer model was used to investigate a large number of room, seating, and subwoofer configurations. For each configuration simulated, metrics for seat to seat consistency and bass efficiency were calculated and combined in a newly proposed metric, which is intended as an overall figure of merit. The data presented has much practical value in small room design for new rooms, or even for modifying existing configurations.
Convention Paper 8748 (Purchase now)
P10-6 Modeling the Large Signal Behavior of Micro-Speakers—Wolfgang Klippel, Klippel GmbH - Dresden, Germany
The mechanical and acoustical losses considered in the lumped parameter modeling of electro-dynamical transducers may become a dominant source of nonlinear distortion in micro-speakers, tweeters, headphones, and some horn compression drivers where the total quality factor Qts is not dominated by the electrical damping realized by a high force factor Bl and a low voice resistance Re. This paper presents a nonlinear model describing the generation of the distortion and a new dynamic measurement technique for identifying the nonlinear resistance Rms(v) as a function of voice coil velocity v. The theory and the identification technique are verified by comparing distortion and other nonlinear symptoms measured on micro-speakers as used in cellular phones with the corresponding behavior predicted by the nonlinear model.
Convention Paper 8749 (Purchase now)
P10-7 An Indirect Study of Compliance and Damping in Linear Array Transducers—Richard Little, Far North Electroacoustics - Surrey, BC, Canada
A linear array transducer is a dual-motor, dual-coil, multi-cone, tubularly-shaped transducer whose shape defeats many measurement techniques that can be used to examine directly the force-deflection behavior of its diaphragm suspension system. Instead, the impedance curve of the transducer is compared against theoretical linear models to determine best-fit parameter values. The variation in the value of these parameters with increasing input signal levels is also examined.
Convention Paper 8750 (Purchase now)
P10-8 Bandwidth Extension for Microphone Arrays—Benjamin Bernschütz, Cologne University of Applied Sciences - Cologne, Germany; Technical University of Berlin - Berlin, Germany
Microphone arrays are in the focus of interest for spatial audio recording applications or the analysis of sound fields. But one of the major problems of microphone arrays is the limited operational frequency range. Especially at high frequencies spatial aliasing artifacts tend to disturb the output signal. This severely restricts the applicability and acceptance of microphone arrays in practice. A new approach to enhance the bandwidth of microphone arrays is presented, which is based on some restrictive assumptions concerning natural sound fields, the separate acquisition and treatment of spatiotemporal and spectrotemporal sound field properties, and the subsequent synthesis of array signals for critical frequency bands. Additionally, the method can be used for spatial audio data reduction algorithms.
Convention Paper 8751 (Purchase now)