Transducers—Part 1

Wednesday, October 18, 2:00 pm — 5:00 pm (Rm 1E11)

Chair:
D. B. (Don) Keele, Jr., DBK Associates and Labs - Bloomington, IN, USA

P04-1 Estimation of Magnitude Response of Reflecting Loudspeaker System in Listening Area Using Near-Box Measurement—Ge Zhu, Nanjing University - Nanjing, China; Ziyun Liu, Nanjing University - Nanjing, China; Yong Shen, Nanjing University - Nanjing, Jiangsu Province, China; Yuchen Shen, Nanjing University - Nanjing, China
This paper presents a simple and robust method to estimate the general magnitude response in reflecting loudspeaker systems. The method utilizes statistical acoustics and is based on near-box impulse response measurement. This measurement holds information across the entire listening area after truncation post-processing. The estimation was investigated in different acoustic environments, which lead to that the more diffusive the room is, the more precise result can be achieved. Measured response can be a reliable reference for correction system in reflecting loudspeaker system. 

P04-2 Optimal Modulator with Loudspeaker Parameter Inclusion—Nicolai Dahl, Technical University of Denmark - Lyngby, Denmark; Niels Elkjær Iversen, Technical University of Denmark - Kogens Lyngby, Denmark; Arnold Knott, Technical University of Denmark - Kgs. Lyngby, Denmark
Today most class-D amplifier designs are able to deliver high efficiency and low distortion. However, the effect of parasitic component and speaker dynamics are not taken into account resulting in a degradation of the performance. This paper proposes a new PWM modulator that is able to capture an arbitrary amount of dynamics through optimization-based design methods. This makes it possible to include the parasitic components in the amplifier and the loudspeaker parameters in the design, thus creating a more linear response. 

P04-3 Fast Loudspeaker Measurement in Non-Anechoic Environments—Christian Bellmann, Klippel GmbH - Dresden, Germany; Wolfgang Klippel, Klippel GmbH - Dresden, Germany
The evaluation of the loudspeaker performance requires a measurement of the sound pressure output in the far field of the source under free field condition. If the available test room does not fulfil this condition, it is common practice to generate a simulated free field response by separating the direct sound from the room reflection based on windowing and holographic processing. This paper presents a new technique that performs a filtering of the measured sound pressure signal with a complex compensation function prior to other time and frequency analysis. The influence of room, nearfield and positioning error is compensated in the measured fundamental and nonlinear distortion characteristics. Different methods are presented for the generation of the compensation function based on a reference response measured under anechoic conditions and a test response measured under in-situ conditions. Benefits and particularities are demonstrated by practical measurements using different kinds of test signals.  

P04-4 Analog Circuit Model for Loudspeakers including Eddy Current Behavior and Suitable for Time Domain Simulation—Stephen C. Thompson, Pennsylvania State University - State College, PA, USA; Daniel M. Warren, GN Advanced Science - Glenview, IL, USA
This paper presents two analog circuit models for the blocked electrical impedance for a moving coil loudspeaker. The first includes an exact model of the effects of eddy currents as derived by Vanderkooy. The model is implemented using a partial fraction expansion that allows an implementation using conventional electrical circuit components. An alternative circuit suggested by Leach uses fewer components and can model not only a purely semi-inductive behavior, but also other frequency variations that are sometimes observed. Because these eddy current models do not use frequency dependent components, they can be used in time domain simulations of loudspeaker behavior that are capable of modeling mechanical and magnetic nonlinearities. 

P04-5 Use of Repetitive Multi-Tone Sequences to Estimate Nonlinear Response of a Loudspeaker to Music—Pascal Brunet, Samsung Research America - Valencia, CA USA; Audio Group - Digital Media Solutions; William Decanio, Samsung Research America - Valencia, CA, USA; Ritesh Banka, Samsung Research America - Valencia, CA USA; Shenli Yuan, Center for Computer Research in Music and Acoustics (CCRMA), Stanford University - Stanford, CA, USA
Aside from frequency response, loudspeaker distortion measurements are perhaps the most commonly used metrics to appraise loudspeaker performance. Unfortunately the stimuli utilized for many types of distortion measurements are not complex waveforms such as music or speech, thus the measured distortion characteristics of the DUT may not typically reflect the performance of the device when reproducing usual program material. To this end, the topic of this paper will be the exploration of a new multi-tone sequence stimulus to measure loudspeaker system distortion. This method gives a reliable estimation of the average nonlinear distortion produced with music on a loudspeaker system and delivers a global objective assessment of the distortion for a DUT in normal use case. 

P04-6 Non-Invasive Audio Performance Measurement on Wireless Speakers—Srinath Arunachalam, Harman International - South Jordan, UT, USA; Douglas J. Button, Harman International - Northridge, CA USA; Jay Kirsch, Harman International - South Jordan, UT, USA; Meenakshi Barjatia, Salt Lake City, UT, USA
Wireless audio systems are gaining market share due to their portability, flexibility, and simply because users do not want to be entangled in wires. As with any technology, the advantages come with many challenges, one of which is creating a meaningful measurement of performance. In this paper we propose a non-invasive testing methodology  for manufacturers to measure audio performance in their wireless speaker products [3]. The method begins with baseline acoustic measurements using electrical (line-in) inputs, which are used as a reference for measurements of other wireless input types such as Bluetooth and Wi-Fi. The results show the degradations due to the wireless transport.