AES Warsaw 2015
Paper Session P14

P14 - (Lecture) Transducers—Part 2

Saturday, May 9, 14:30 — 17:30 (Room: Królewski)

Aki Mäkivirta, Genelec - Lapinlahti, Finland

P14-1 High Power Efficiency and Broad Flat Radiation Bandwidth of a Parametric Array PMUT LoudspeakerKyounghun Been, POSTECH - Gyeongsangbuk-do, Korea; Younghwan Hwang, POSTECH - Gyeongsangbuk-do, Korea; Yub Je, Agency for Defense Development - Gyeongsangnam-do, Korea; Haksue Lee, Agency for Defense Development - Gyeongsangnam-do, Korea; Wonkyu Moon, POSTECH - Gyeongsangbuk-do, Korea
Parametric Array loudspeakers can generate a sound beam using nonlinear acoustic interactions, widely known as “Parametric Array,” that can enable private listening in a public area. Parametric array loudspeakers can be applied to many applications, such as information technology devices, that require a high power efficiency and wide bandwidth. In a previous study, a piezoelectric micro-machined ultrasonic transducer (PMUT) is shown to be an efficient unit for a parametric array loudspeaker. In this paper we will describe realization of a parametric array loudspeaker with high power efficiency (up to 71%) and wide flat radiation bandwidth (19.5 kHz, difference frequency wave with equalization), which consists of an array of PMUTs with two resonance frequencies (f1 = 100 kHz, f2 = 110 kHz) and use of “out-of-phase” driving techniques.
Convention Paper 9314 (Purchase now)

P14-2 Slit-Firing Sound Plate design with Slim Elliptical SpeakerGyeong-Tae Lee, DMC R&D Center, Samsung Electronics Co. - Suwon-si, Gyeonggi-do, Korea; Jong-Bae Kim, Samsung Electronics - Suwon-si, Gyeonggi-do, Korea; Seong-Ha Son, Samsung Electronics Co. Ltd. - Suwon, Gyeonggi-do, Korea
Slim design has emerged recently as a new form factor for the speaker system of an electronic device. However, this form factor is disadvantageous to sound performance because of the narrow space for a speaker unit. In this paper, to overcome this drawback, we designed Slit-Firing Sound Plate, which is a slim speaker system using diffraction through a slit, and developed a slim elliptical speaker that is optimized for the boundary conditions for the slit. After building and tuning a prototype, the sound performance of the prototype was assessed by measuring and examining frequency response, transient response, and directivity beam pattern. As a result, proposed novel design shows high performance that makes it suitable for the application of slim electronic devices.
Convention Paper 9315 (Purchase now)

P14-3 Improvements in Elimination of Loudspeaker Distortion in Acoustic MeasurementsFinn T. Agerkvist, Technical University of Denmark - Kgs. Lyngby, Denmark; Antoni Torras-Rosell, Danish National Metrology Institute - Lyngby, Denmark; Richard McWalter, Technical University of Denmark - Lyngby, Denmark
This paper investigates the influence of nonlinear components that contaminate the linear response of acoustic transducers and presents improved methods for eliminating the influence of nonlinearities in acoustic measurements. The method is evaluated with pure sinusoidal signals as well as swept sine signals and is tested on models of memoryless nonlinear systems as well as nonlinear loudspeakers. The method is shown to give a clear benefit over existing methods. Two techniques that improve the signal to noise ratio are demonstrated: the first uses more measurement level than the number of orders to be separated, whereas the other one is based on standard Tikhonov regularization. Both methods are shown to significantly improve the signal to noise ratio.
Convention Paper 9316 (Purchase now)

P14-4 Flux Modulation in the Electrodynamic LoudspeakerMorten Halvorsen, PointSource Acoustics - Roskilde, Denmark; Carsten Tinggaard, PointSource Acoustics - Roskilde, Denmark; Finn T. Agerkvist, Technical University of Denmark - Kgs. Lyngby, Denmark
This paper discusses the effect of flux modulation in the electrodynamic loudspeaker with main focus on the effect on the force factor. A measurement setup to measure the AC flux modulation with static voice coil is explained and the measurements show good consistency with FEA simulations. Measurements of the generated AC flux modulation shows that eddy currents are the main source to magnetic losses in form of phase lag and amplitude changes. Use of a copper cap shows a decrease in flux modulation amplitude at the expense of increased power losses. Finally, simulations show that there is a high dependency between the generated AC flux modulation from the voice coil and the AC force factor change.
Convention Paper 9317 (Purchase now)

P14-5 Validation of Power Requirement Model for Active LoudspeakersHenrik Schneider, Technical University of Denmark - Kgs. Lyngby, Denmark; Anders N. Madsen, Technical University of Denmark - Kongens Lyngby, Denmark; Ruben Bjerregaard, Technical University of Denmark - Kongens Lyngby, Denmark; Arnold Knott, Technical University of Denmark - Kgs. Lyngby, Denmark; Michael A. E. Andersen, Technical University of Denmark - Kgs. Lyngby, Denmark
The actual power requirement of an active loudspeaker during playback of music has not received much attention in the literature. This is probably because no single and simple solution exists and because a complete system knowledge from input voltage to output sound pressure level is required. There are, however, many advantages that could be harvested from such knowledge like size, cost, and efficiency improvements. In this paper a recently proposed power requirement model for active loudspeakers is experimentally validated and the model is expanded to include the closed and vented type enclosures in addition to the main loudspeaker non-linearities.
Convention Paper 9318 (Purchase now)

P14-6 Subwoofers in Rooms: Stereophonic ReproductionJuha Backman, Microsoft - Espoo, Finland
A study based on computational model of interaural level and time differences at the lowest audio frequencies, often reproduced through subwoofers, is presented. This work studies whether interaural differences can exist, and if they do, what kind of relationship there is between the loudspeaker direction and the interaural differences when monophonic and stereophonic subwoofer arrangements are considered. The calculations are made for both simple amplitude panned signals and for simulated microphone signals. The results indicate that strong narrow-band differences can exist, especially near room eigenfrequencies when the listener is close to nodes of the room modes and that the modes of the recording room can have an effect on the sound field of the listening room. In addition to the computational results an analysis of interchannel level differences in recordings is presented, confirming the computational model.
Convention Paper 9319 (Purchase now)

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