v3.1, 20040408, ME

Session Q Tuesday, May 11 09:30 h–12:00 h
AUDIO RECORDING AND REPRODUCTION & HIGH- RESOLUTION AUDIO
Chair: Malcolm Hawksford, University of Essex, Colchester, UK

Q-1 Respecting the Sound—From Aural Event to Ear Stimulus— George Brock-Nannestad, Patent Tactics, Gentofte, Denmark
Graphical or real-time interactive analysis of recorded sound occurred at least 20 years before the invention of reproducible sound in 1877. Scientifically reproduced sound quickly found its way into phonetics and musicology. Early commercial sound recording for entertainment retained an aura of reproduction of a real sound event and prescribed certain calibration features. After commercial success was ensured around 1913, manipulation techniques were developed and refined. The later analog years demonstrated imaginative thinking that came to a climax when fast digital technology enabled satisfactory signals that only contained what the ear requires and no more. The dissociation from the total real sound was complete. This paper provides a balanced, well-documented historical overview of the techniques and their consequences.
Q-2 A New Approach to Effective Dither in Delta-Sigma Modulation Systems—James Angus, The University of Salford, Greater Manchester, UK
This paper presents a new approach to dither in Sigma-Delta Modulation (SDM) systems. In particular it clarifies the position of the overload point in 1-bit SDM systems and presents several overload control methods with comparisons of their efficacy. It then goes on to examine the problem of applying dither to 1-bit systems and describes a new approach to applying high levels of dither. It presents results, which show that such dither can be effective in SDM systems.
Q-3 Ultra High-Resolution Audio Formats for Mastering Applications—Malcolm Hawksford, University of Essex, Essex, UK
To process audio signals prior to DSD and LPCM delivery, an audio data format is required that possesses a resolution substantially greater than the final release form. A number of strategies are presented capable of enhanced resolution. Techniques using the step-back algorithm are extended to include a multilevel quantizer but where the amplitude range is finite. An earlier scheme based upon multilevel SDM and multistage lossless differential coding is enhanced by incorporating more aggressive noise shaping implemented by means of parametric noise shaping previously used for binary SDM.
Q-4 Voided Space-Charge Electrets—Piezoelectric Transducer Materials for Electro-Acoustic Applications— Michael Wegener, Steffen Bergweiler, Werner Wirges, Andreas Pucher, Reimund Gerhard-Multhaupt, University of Potsdam, Potsdam, Germany
Voided space-charge electrets, such as cellular polypropylene, have recently been developed as piezoelectric materials that exhibit strong electromechanical thickness oscillations corresponding to high piezoelectric coefficients of around 500 pC/N and very good acoustical matching to air (low density of typically around 0.5 g/cm3 and low sound speed). Here, we discuss different aspects of the manufacture and the applicability of cellular polypropylene films as transducer materials at high frequencies and for ultrasound. The frequency response up to 90 kHz and the directivity patterns for several transducer geometries were investigated. Second- and third- order harmonic distortions and the power consumption of cellular polypropylene films in acoustic transducers are also described. Our results demonstrate that the relatively new ferroelectret films are very attractive for a range of device applications.
Q-5 Wind & Weather—Martin Schneider, Georg Neumann GmbH, Berlin, Germany
Microphones are used in all environments, especially for outdoor locations, but also in studio surroundings, wind and humidity characteristics of microphones and their relevant accessories are of interest. This paper presents acoustic and noise measurements plus audio examples of different types of microphones under climatically adverse circumstances with diverse protective accessories like foam windshields, wind baskets, etc. Application guidelines for recording engineers are deduced.