144th AES CONVENTION Engineering Brief EB03: Signal Processing/Audio Effects & Instrumentation/Measurements/Forensics

AES Milan 2018
Engineering Brief EB03

EB03 - Signal Processing/Audio Effects & Instrumentation/Measurements/Forensics

Friday, May 25, 09:30 — 11:15 (Scala 2)

Aki Mäkivirta, Genelec Oy - Iisalmi, Finland

EB03-1 SysId—A System Identification Measurement PackageJont Allen, University of Illinois - Urbana, IL, USA
SysID is a computer program that was developed c1980 at Bell Labs, for measurement of linear and nonlinear systems. At that time it was ported to the IBM-PC, and was sold by the Ariel Corp., Highland Park, NJ. Today it is a Matlab/Octave script that works with special hardware manufactured by Mimosa Acoustics of Champaign IL. SysID can measure the complex frequency response and impulse response of any linear system, such as loudspeakers, earphones, and rooms. When coupled with Matlab/Octave, it may be used as an audio-band network analyzer providing a pole-zero analysis of measured complex impedance, either electrical or acoustical. By using synchronous analysis, SysID complements spectrum analyzer functions, and in many cases, can extend the function of a two-channel spectrum analyzer, quickly resulting in highly accurate magnitude and phase results, limited only by the bit-accuracy of the codecs. It can more accurately characterize harmonic distortion and inter-modulation distortion, group delay, phase, impedance, and many other important system features, in near real time, along with a pole-zero analysis. In this presentation I will describe the theory behind SysID, and give a demonstration on the hand-held portable system. There is a long history behind such system. For example a number-theory method called MLS is believed by many to be superior, however this is a topic that needs clarification. MLS uses binary sequences, and therefore cannot directly measure TDH+N, or inter-modulation distortion. These issues are easily overcome by using int-32 sequences having powers of 2 sequence lengths. SysID has been used to measure auditoriums, conference rooms, loudspeaker impulse responses, cochlear potentials, ear canal impedance and reflectance, and many other two-port measurements such as a detailed loudspeaker analysis. The system is used in ECE-403 by students to analyze loud speaker characteristics, and was used to characterize and then model hearing aid receivers [1, 2].
Engineering Brief 421 (Download now)

EB03-2 Capacitor Distortion in High-Order Active FiltersDouglas Self, The Signal Transfer Company - London, UK
Some non-electrolytic capacitor types such as polyester generate distortion when they have a significant signal voltage across them. This can be avoided by using polypropylene or polystyrene types but they are larger and more expensive. I have previously shown that in 2nd-order Sallen & Key filters, both lowpass and highpass, only one of the two capacitors has to be of the expensive sort to obtain the same freedom of distortion achieved with two. The Geffe configuration allows 3rd and 4th-order filters to be realized economically in one stage, and it is shown that here too only one linear capacitor is required in both lowpass and highpass cases, saving a lot of money.
Engineering Brief 422 (Download now)

EB03-3 Graphical Development Design for a Heterogeneous DSP Core ArchitectureMiguel Chavez, Analog Devices - Wilmington, MA, USA
For over 15 years, Analog Devices has continued improving its graphical programming environment to support several, audio specific and general purpose digital signal processors (DSPs). As of 2016, all supported processors have either contained single or dual DSP cores whereas both of them have had the same architecture. With the need to have a heterogeneous DSP architecture the team had the challenge to program both cores within the same environment. This paper describes challenges, trade-offs and design decisions made when programming a new heterogeneous DSP core architecture.
Engineering Brief 423 (Download now)

EB03-4 Room Acoustic Measurements with Logarithmic Sine Sweeps on Android PhonesLorenzo Rizzi, Suono e Vita - Acoustic Engineering - Lecco, Italy; Giulio Scotti, Suonoevita Ingegneria - Lecco, Italy; Gabriele Ghelfi, Suono e Vita - Acoustic Engineering - Lecco, Italy
An application for room acoustics measurements has been developed for Android devices: its novelty represents the use of the logarithmic sine sweep method, which is better than typical direct methods used so far. The article describes the main points of the design phase and stresses the instrument on-site testing results in common use rooms. The testing of this Android instrument gives insights on small-room acoustics and on acoustical parameters measurement quality.
Engineering Brief 424 (Download now)

EB03-5 DirPat—Database and Viewer of 2D/3D Directivity Patterns of Sound Sources and ReceiversManuel Brandner, University of Music and Performing Arts Graz - Graz, Austria; Matthias Frank, University of Music and Performing Arts Graz - Graz, Austria; Daniel Rudrich, Institute of Electronic Music and Acoustics Graz - Graz, Austria
A measurement repository (DirPat) has been set up to archive all 3D and 2D directivity patterns measured at the Institute of Electronic Music and Acoustics, University of Music and Performing Arts in Graz. Directivity measurements have been made of various loudspeakers, microphones, and also of human speakers/singers for specific phonemes. The repository holds time domain impulse responses for each direction of the radiating or incident sound path. The data can be visualized with the provided 2D and 3D visualization scripts programmed in MATLAB. The repository is used for ongoing scientific research in the field of directivity evaluation of sources or receivers regarding localization, auditory perception, and room acoustic modeling.
Engineering Brief 425 (Download now)

EB03-6 The Anatomy, Physiology, and Diagnostics of Smart Audio DevicesXinhui Zhou, Audio Precision - Beaverton, OR, USA; Mark Martin, Audio Precision - Beaverton, OR, USA; Jayant Datta, Audio Precision - Beaverton, OR, USA; Vijay Badawadagi, Audio Precision - Beaverton, OR, USA
Smart audio devices are becoming ubiquitous and their popularity has been skyrocketing. By current standards, a smart audio device is voice-controlled through interaction with an Internet-based intelligent virtual assistant and usually provides access to remote repositories of music or information. This paper focuses on the smart speakers (e.g., Amazon Echo, Google Home, etc.)—the most popular smart audio device. Though they are usually composed of relatively simple audio components, these devices incorporate very sophisticated audio signal processing, a plethora of audio pathways, and functional audio subsystems—posing significant challenge in testing. This paper explores the audio subsystems and pathways found on this type of device and suggests ways to test and validate their functionality and performance.
Engineering Brief 426 (Download now)

EB03-7 Proposed AES Test Standard for Specifying Continuous and Short-Term Maximum Power and SPL for Electronic and Electro-Acoustic Systems: Part 1D. B. (Don) Keele, Jr., DBK Associates and Labs - Bloomington, IN, USA; Steven Hutt, Equity Sound Investments - Bloomington, IN, USA; Marshall Kay, Keysight Technologies - Apex, NC, USA; Hugh Sarvis, Presonus Audio Electronics-Worx Audio Technologies - Baton Rouge, LA, USA
This paper describes a proposed test method that allows both the continuous and short-term maximum peak output and SPL for electronic and electroacoustic systems to be measured. Systems such as power amplifiers, loudspeakers, and sound reinforcement/cinema systems can be measured and specified over the complete audible range. The test is divided into two parts that individually assesses: (1) the system’s broadband continuous maximum output using various steady-state low-crest-factor test signals and (2) the system’s short-term narrow-band maximum output using high-crest-factor test signals. The combination of both tests completely specifies the system’s maximum output on a continuous and short-term narrow-band basis. A future Part 2 paper will go into detail concerning the tests and will illustrate with measured test results.
Engineering Brief 427 (Download now)

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