Authors: Wilson, David
[feature article] Technical Committees are centers of technical expertise within the AES. Coordinated by the AES Technical Council, the Technical Committees track trends in audio in order to recommend to the Society special papers sessions, workshops, standards, projects, publications, and awards in their fields. In order to facilitate this advisory role of the Technical Council, every two years the chairs of all Technical Committees report to the Technical Council by listing the most current technical and policy matters the committees are aware of. The short reports presented here identify, from the global perspective, current research trends and interests in various technical fields of audio.
Authors: Wilson, David
The National Radio Systems Committee's testing and evaluation program for in-band onchannel digital audio broadcast systems is described. The results of laboratory and field tests performed during 2001 on iBiquity Digital Corporation's AM-band and FM-band IBOC DAB systems are reported. The conclusions drawn from the laboratory and field test results are also reported, and implications for the future are discussed.
Authors: Raangs, R.; Druyvesteyn, W. F.; De Bree, H. E.
The sound intensity in a sound field can be determinated from two acoustical measurements method, the sound intensity is calculated by means of two spaced microphones. Another method, the p-u method, uses a pressure sensor to measure the sound particle velocity. Using the p-u method, measurements performed with a low-cost intensity probe and a computer soundcard combined with an open-source software show good agreement with results obtained with a p-p probe.
Authors: Mäkivirta, Aki; Antsalo, Poju; Karjalainen, Matti; Välimäki, Vesa
The control of excessively long decays in a listening room with strong low-frequency modes is problematic, expensive, and sometimes impossible with conventional passive means. A systematic methodology is presented to design active modal equalization able to selectively reduce the mode decay rate of a loudspeaker-room system at low frequencies in the vicinity of a sound engineer's listening location. Modal equalization is able to increase the rate of initial sound decay at mode frequencies, and can be used with conventional magnitude equalization to optimize the reproduced sound quality. Two methods of implementing active modal equalization are proposed. The first modifies the primary sound such that the mode decay rates are controlled. The second uses separate secondary radiators and controls the mode decays with additional sound fed into the secondary radiators. Case studies are presented of implementing active modal control according to the first method.
Authors: Klippel, Wolfgang
The voice-coil peak displacement Xmax is an important driver parameter for assessing the maximum acoustic output at low frequencies. The existing standard AES2-1984 defines the peak displacement Xmax by measuring harmonic distortion in either voice-coil current or displacement. This freedom of choice gives completely different and controversial results. After a critical review of this performance-based technique, an amendment of this method is suggested. Alternatively, a parameter-based method is developed giving more detailed information about the cause of the distortion, limitations, and defects. The relationship between performance-based and parameter-based methods is discussed, and both techniques are tested with real drivers.
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