2002 January/February, Vol 50 Number 1/2

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   47
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   58
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
Upcoming Meetings   87
Sound Track   88
New Products and Developments   90
Available Literature   92
Membership Information   93
Advertiser Internet Directory   97
In Memoriam   98
AES Special Publications   101
Sections Contacts Directory   106
AES Conventions and Conferences   112

FPO For the cover:

2002 January/February, Vol 50 Number 1/2

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