Transducers

Wednesday, October 16, 1:30 pm — 5:00 pm (1E11)

Chair:
Todd Welti, Harman International Inc. - Northridge, CA, USA

P05-1 Nonlinear Control of Loudspeaker Based on Output Flatness and Trajectory Planning—Pascal Brunet, Samsung Research America - Valencia, CA USA; Audio Group - Digital Media Solutions; Glenn S. Kubota, Samsung Research America - Valencia, CA, USA
A loudspeaker is inherently nonlinear and produces timbre alterations, roughness, harshness, lack of clarity, and modulation noise. This may impair reproduction quality and speech intelligibility. These issues increase rapidly with high levels and especially high bass levels. Industrial design and marketing constraints demand smaller speaker systems without sacrificing sound output level. This results in higher distortion. To obtain "big bass from little boxes," an anti-distortion system is needed. We present a new approach that is based on the direct control and linearization of the loudspeaker diaphragm displacement that allows the maximization of the bass output and the minimization of the nonlinearities while keeping the diaphragm displacement within the range of safe operation.

P05-2 Perceptual Assessment of Distortion in Low-Frequency Loudspeakers—Louis Fielder, Retired - Millbrae, CA, USA; Michael Smithers, Dolby Laboratories - Sydney, NSW, Australia
A perceptually-driven distortion metric for loudspeakers is proposed that is based on a critical-band spectral comparison of the distortion and noise to an appropriate masking threshold. The loudspeaker is excited by a sine-wave signal composed of windowed 0.3 second bursts. Loudspeaker masking curves for sine waves between 20–500 Hz are derived from previously published ones for headphone distortion evaluation and expanded to curves at 1 decibel increments by linear interpolation and extrapolation. For each burst, the ratios of measured distortion and noise levels to the appropriate masking curve values are determined for each critical band starting at the second harmonic. Once this is done the audibility of all these contributions are combined into various audibility values.

P05-3 Rethinking Flat Panel Loudspeakers—An Objective Acoustic Comparison of Different Speaker Categories—Benjamin Zenker, Technical University Dresden - Dresden, Germany; Hommbru GmbH - Reichenbach, Germany; Sebastian Merchel, TU Dresden - Dresden, Germany; M. Ercan Altinsoy, TU Dresden - Dresden, Germany
The home entertainment market is growing, but connected devices like multi-room and streaming loudspeakers are increasingly replacing traditional audio systems. Compromises in the acoustic quality are made to satisfy additional requirements such as smaller, lighter, and cheaper products. The number of smart speakers sold suggests that the customers accept speakers with lower acoustical quality for their daily use. Concepts like soundbars aim to achieve better spatial reproduction but try to stay visually unobtrusive. Thanks to the low visual profile flat panel loudspeakers give opportunities for invisible integration. This paper presents an objective acoustic comparison of four speaker categories: smart speaker, flat panel, soundbar, and studio monitor. The comparison reveals that recent technological advances could make flat panel loudspeakers an alternative.

P05-4 Modelling and Measurement of Nonlinear Intermodal Coupling in Loudspeaker Diaphragm Vibrations—William Cardenas, ORA Graphine Audio Inc. - Montreal, Quebec, Canada
Accurate prediction of the nonlinear transfer response of loudspeakers in the full band is relevant to optimize the development of audio products. Small size, light, and efficient transducers require low density and thin diaphragms, which may vibrate nonlinearly even at low amplitudes impairing the sound quality. This paper proposes an extension of the existing transducer model comprising breakup modes with geometrical nonlinearities, adding the nonlinear coupling effect between the piston mode and the breakup modes responsible for large intermodulation problems. A novel measurement technique to estimate the breakup frequency modulation induced by the piston mode excursion is presented, the model is validated with measurements of harmonic and intermodulation distortion and other symptoms relevant for assessment of acoustic performance.

P05-5 Sound Capture by Microphone Vibration inside Playback Devices—Rivanaldo De Oliveira, Qualcomm Technologies, Inc. - San Diego, CA, USA
Integration of voice capture into devices that formerly were used only as a sound source, or that now need to include the ability to interface with a variety of cloud-provided services available to users and/or expand voice control capability to otherwise simple devices has become commonplace, and integration of multiple microphones inside a case that houses playback transducers requires careful attention to certain design aspects as will be discussed in this article where a prototype of a "Smart Speaker" will be used as an example.

P05-6 Low Deviation and High Sensitivity—Optimized Exciter Positioning for Flat Panel Loudspeakers by Considering Averaged Sound Pressure Equalization—Benjamin Zenker, Technical University Dresden - Dresden, Germany; Hommbru GmbH - Reichenbach, Germany; Shanavaz Sanjay Abdul Rawoof, TU Dresden - Dresden, Germany; Sebastian Merchel, TU Dresden - Dresden, Germany; M. Ercan Altinsoy, TU Dresden - Dresden, Germany
Loudspeaker panels represent a class of loudspeakers, whose electrical, mechanical, and acoustical properties differ completely from conventional loudspeakers. However, the acoustic properties are mostly associated with lower performance. The position of the excitation is one of the crucial parameters to optimize multiple parameters such as the frequency response in terms of linearity and sensitivity. This paper describes an approach to find the best excitation position for an exemplary distributed mode loudspeaker (DML) by considering efficiency and the averaged sound pressure equalization. An evaluation of the measured response in the horizontal plane of 25 excitation positions is presented and an optimization algorithm is used to filter every position to a certain acoustical quality standard.

P05-7 A Comparison of Test Methodologies to Personalize Headphone Sound Quality—Todd Welti, Harman International Inc. - Northridge, CA, USA; Omid Khonsaripour, Harman International - Northridge, CA, USA; Sean Olive, Harman International - Northridge, CA, USA; Dan Pye, Harman International - Northridge, CA, USA
There exist many different methods to gather subjective equalization preference data from listeners. From one method to another there are generally tradeoffs between speed, accuracy, and ease of use. In this study four different types of test were compared to see which tests performed the best in each of these categories. The purpose was to select the best methods for headphone personalization applications for mobile devices. All four tests involve test subjects setting filter gain values for bass and treble shelving filters, and thus selecting their preferred response curves for listening to music through headphones. The results of each test, the time taken to complete them, and the ease of use based on a post-test questionnaire are presented.