JOURNAL OF THE AUDIO ENGINEERING SOCIETY AES AUDIO/ACOUSTICS/APPLICATIONS VOLUME 50 NUMBER 1/2 2002 JANUARY/FEBRUARY CONTENT President’s Message........................................................................................................Garry Margolis 3 PAPERS Fourth-Order Symmetrical Band-Pass Loudspeaker Systems ....................................................................................................Grzegorz P.Matusiak and Andrzej B. Dobrucki 4 The analysis of fourth-order band-pass loudspeaker systems based on the well-known Thiele, Small, and Benson theory is presented using a reactance transformation method. By comparing the acoustic analog circuit with the transfer function obtained from the reactance transformation, the results allow the symmetry condition to be determined. The resulting system has advantages over closed-box and vented-box high-pass systems in terms of power and efficiency. Maximizing Performance from Loudspeaker Ports .......Alex Salvatti, Allan Devantier, and Doug J. Button 19 The low-frequency performance of a loudspeaker is significantly enhanced by the use of tapered ports, but there are numerous trade-offs involving the size of the port and the input and output tapers. Design issues include the effectiveness of heat transfer, amount of turbulence created, air velocity, smoothness of the taper, symmetry of the two tapers, effective mass in the port, and the contribution to the frequency response. Suggested design rules are based on extensive empirical studies. ENGINEERING REPORTS Wavetable Matching of Inharmonic String Tones ............................Clifford So and Andrew B. Horner 46 A new wavetable matching technique for inharmonic music tones, such as a violin with vibrato, shows good spectral matching and adequate frequency resolution. Confirmation with listening tests significantly improves the perceived matching but degrades performance on harmonic trumpet tones compared to simple wavetable matching. The new method offers more than a three-fold improvement over additive synthesis for these cases, but for harmonic tones the original matching technique should be used. Localization of Virtual Sound as a Function of Head-Related Impulse Response Duration ...........................................................................Melis A. Senova, Ken I. McAnally, and Russell L. Martin 57 The localization accuracy of subjects using headphones was determined as a function of the duration of the head-related impulse response. Unlike previous studies, there was a gradual decrease in accuracy starting at 10 ms and becoming drastically worse at about 0.5 ms. Durations of more than 10 ms result in performance indistinguishable from free-field localization. Shorter durations are equivalent to smoothing the frequency response and thereby removing the fine detail unique to each subject’s own ears. CORRECTIONS Correction to “Multitone Testing of Sound System Components—Some Results and Conclusions, Part 1: History and Theory” ...........................Eugene Czerwinski, Alexander Voishvillo, Sergei Alexandrov, and Alexander Terekhov 66 STANDARDS AND INFORMATION DOCUMENTS AES Standards Committee News........................................................................................................... 67 ATM networking; acoustics measurement; EMC; IEEE1394 networks; network and file transfer Call for Comment on DRAFT AES47-xxxx, DRAFT AES standard on digital audio digital input-output interfacing transmission of digital audio over asynchronous transfer mode (ATM) networks............... 67 Call for Comment on REAFFIRMATION of AES18-1996, AES recommended practice for digital audio engineering — Format for the user data channel of the AES digital audio interface............. 67 Call for Comment on REAFFIRMATION of AES20-1996, AES recommended practice for professional audio — Subjective evaluation of loudspeakers............................................................ 68 Call for Comment on REAFFIRMATION of AES27-1996, AES recommended practice for forensic purposes — Managing recorded audio materials intended for examination..................................... 68 Call for Comment on WITHDRAWAL of AES15-1991, AES recommended practice for sound- reinforcement systems — Communications interface (PA-422) ......................................................... 68 FEATURES Audible Alarms for the Hearing Impaired ..................................................................John Vanderkooy 73 Education News....................................................................................................................................... 81 113th Convention, Los Angeles, Call for Papers .................................................................................. 100 DEPARTMENTS News of the Sections ..........................................82 Advertiser Internet Directory..............................97 Upcoming Meetings ............................................87 In Memoriam ........................................................98 Sound Track..........................................................88 AES Special Publications .................................101 New Products and Developments......................90 Sections Contacts Directory ............................106 Available Literature .............................................92 AES Conventions and Conferences ................112 Membership Information.....................................93 JOURNAL OF THE AUDIO ENGINEERING SOCIETY AES AUDIO/ACOUSTICS/APPLICATIONS VOLUME 50 NUMBER 3 2002 MARCH CONTENT PAPERS Effect Design, Part 3 Oscillators: Sinusoidal and Pseudonoise......................................Jon Dattorro 115 This is the third of a three-part series that provides a tutorial reference for those signal processing algorithms that are of particular interest to music. In this part, the issues of low-frequency sinusoidal oscillators and sonically pleasant pseudorandom noise generators are reviewed, compared, and analyzed. Both topics actually have deep issues even though the signal definitions are simple. The historical background, pertinent references, and appendices provide the reader with a comprehensive foundation in these subjects. Reproducing Low-Pitched Signals through Small Loudspeakers .........Erik Larsen and Ronald M. Aarts 147 Because small-volume loudspeakers are unable to reproduce low frequencies, alternative methods can be used to create the illusion of those frequencies by taking advantage of a phantom-pitch phenomenon—the perception of a fundamental when only its harmonics are present. The low frequencies below the loudspeaker cutoff point are extracted from the wide-band signal, nonlinearly processed, filtered again, and finally injected into the path of the main signals. Listeners prefer this artificial bass in comparison to flat reproduction through a small loudspeaker. A particular implementation of phantom pitch is illustrated. Generating Source Streams for Extralinguistic Utterances............................Eduardo Reck Miranda 165 Most speech-synthesis systems do not provide a mechanism for creating nonspeechlike signals, such as sounds like boom, meow, gurgles, and genetic vocal noises. To avoid the mechanical-sounding attributes of other approaches, the author adapts a cellular automata control of the spectral parameters. The array of parameters is updated according to a set of rules to create transitions between states using the values of the neighboring cells as input parameters. While this approach works well to create natural sounds, there is insufficient knowledge about how to create an imagined sound. ENGINEERING REPORTS Estimating the Loudspeaker Response when the Vent Output is Delayed...................Neville Thiele 173 A new wavetable-matching technique for inharmonic music tones, such as a violin with vibrato, shows good spectral matching and adequate frequency resolution. Confirmation with listening tests significantly improves the perceived matching but degrades performance on harmonic trumpet tones compared to simple wavetable matching. The new method offers more than a three-fold improvement over additive synthesis for these cases, but for harmonic tones the original matching technique should be used. STANDARDS AND INFORMATION DOCUMENTS AES Standards Committee News........................................................................................................... 176 Audio connectors FEATURES 112th Convention Preview, Munich........................................................................................................ 178 Calendar................................................................................................................................................. 180 Exhibitors............................................................................................................................................... 181 Exhibitor Previews ................................................................................................................................ 184 113th Convention, Los Angeles, Call for Workshops Participants ................................................... 206 DEPARTMENTS News of the Sections ........................................201 In Memoriam ......................................................212 Upcoming Meetings ..........................................203 AES Special Publications .................................213 Sound Track........................................................205