AES Munich 2009
Paper Session P9
Signal Analysis, Measurements, Restoration
Friday, May 8, 09:00 — 12:30
Chair: Jan Abildgaard Pedersen
P9-1 Some Improvements of the Playback Path of Wire Recorders—Nadja Wallaszkovits, Phonogrammarchiv Austrian Academy of Sciences - Vienna, Austria; Heinrich Pichler, Audio Consultant - Vienna, Austria
The archival transfer of wire recordings to the digital domain is a highly specialized process that incorporates a wide range of specific challenges. One of the basic problems is the format incompatibility between different manufacturers and models. The paper discusses the special design philosophy, using the tone control network in the record path as well as in the playback path. This tone control circuit causes additional phase and group delay distortions. The influence and characteristics of the tone control (which was not a priori present with every model) is discussed and analog phase correction networks are described. The correction of phase errors is outlined. As this format has been obsolete for many decades, a high quality archival transfer can only be reached by modifying dedicated equipment. The authors propose some possible main modifications and improvements of the playback path of wire recorders, such as signal pickup directly after the playback head, introducing a high quality preamplifier, followed by analog phase correction and correction of the amplitude characteristics. Alternatively signal pickup directly after the playback head, introducing a high quality preamplifier, followed by digital signal processing to optimize the output signal is discussed.
Convention Paper 7698 (Purchase now)
P9-2 Acoustics of the Crime Scene as Transmitted by Mobile Phones—Eddy B. Brixen, EBB-consult - Smorum, Denmark
One task for the audio forensics engineer is to extract background information from audio recordings. A major problem is the assessment of analyzed telephone calls in general and mobile phones (LPC-algorithms) in particular. In this paper the kind of acoustic information to be extracted from a recorded phone call is initially explained. The parameters used for the characterization of the various acoustic spaces and events in question are described. It is discussed how the acoustical cues should be assessed. The validity of acoustic analyses carried out in the attempt to provide crime scene information like reverberation time is presented.
Convention Paper 7699 (Purchase now)
P9-3 Silence Sweep: A Novel Method for Measuring Electroacoustical Devices—Angelo Farina, University of Parma - Parma, Italy
This paper presents a new method for measuring some properties of an electroacoustical system, for example a loudspeaker or a complete sound system. Coupled with the already established method based on Exponential Sine Sweep, this new Silence Sweep method provides a quick and complete characterization of not linear distortions and noise of the device under test. The method is based on the analysis of the distortion products, such as harmonic distortion products or intermodulation effects, occurring when the system is fed with a wide-band signal. Removing from the test signal a small portion of the whole spectrum, it becomes possible to collect and analyze the not-linear response and the noise of the system in that “suppressed” band. Changing continuously the suppressed band over time, we get the Silence Sweep test signal, which allows for quick measurement of noise and distortion over the whole spectrum. The paper explains the method with a number of examples. The results obtained for some typical devices are presented, compared with those obtained with a standard, state-of-the-art measurement system.
Convention Paper 7700 (Purchase now)
P9-4 Pitch and Played String Estimation in Classic and Acoustic Guitars—Isabel Barbancho, Lorenzo Tardón, Ana M. Barbancho, Simone Sammartino, Universidad de Málaga - Málaga, Spain
In classic and acoustic guitars that use standard tuning, the same pitch can be produced at different strings. The aim of this paper is to present a method based on the time and frequency-domain characteristics of the recorded sound to determine, not only the pitch but also the string of the guitar that has been played to produce that pitch. This system will provide information not only of the pitch of the notes played, but also about how those notes were played. This specific information can be valuable to identify the style of the player and can be used in teaching to play the guitar.
Convention Paper 7701 (Purchase now)
P9-5 Statistical Properties of Music Signals—Miomir Mijic, Drasko Masovic, Dragana Sumarac-Pavlovic, Faculty of Electrical Engineering - Belgrade, Serbia
This paper is concerned with the results of a complex approach to statistical properties of various music signals based on 412 musical pieces classified in 12 different genres. Analyzed signals contain more than 24 hours of music. For each piece time variation of the signal level was found, performed with a 10 ms period of integration in rms calculation and with 90 percent overlap, making a new signal representing the level as a function of time. For each piece the statistical analysis of signal level has been performed by its statistical distribution, cumulative distribution, effective value within complete duration of piece, mean level value, and level value corresponding to maximum of the statistical distribution. The parameter L1, L10, L50, and L99 were extracted from cumulative distributions as numerical indicators of dynamic properties. The paper contains detailed statistical data and averaged data for all observed genres, as well as quantitative data about dynamic range and crest factor of various music signals.
Convention Paper 7702 (Purchase now)
P9-6 Multi-Band Generalized Harmonic Analysis (MGHA) and its Fundamental Characteristics in Audio Signal Processing—Takahiro Miura, Teruo Muraoka, Tohru Ifukube, University of Tokyo - Tokyo, Japan
One of the main problems in sound restoration of valuable historical recordings includes the noise reduction. We have been proposing and continuing to improve the noise reduction method utilized by inharmonic analysis such as GHA (Generalized Harmonic Analysis). Algorithm of GHA frequency extraction enables us to extract arbitrary frequency components. In this paper we aimed at more accurate frequency identification from noisy signals to divide analyzed frequency section into multi-bands before analysis: this algorithm is named as Multi-Band GHA (MGHA). The simulation of frequency analysis in a noise-free condition indicated that MGHA is more effective than GHA for the extraction of low frequency components in the condition of both lower window length and amount of frequency components. However, excluding the case of both lower window length and amount of frequency components, GHA identifies frequency components more precisely. Furthermore the result of frequency analysis in condition with steady noise shows that MGHA can be more effectively applied to the case of short window length, many frequency components, and low S/N.
Convention Paper 7703 (Purchase now)
P9-7 Automatic Detection of Salient Frequencies—Joerg Bitzer, University of Applied Science Oldenburg - Oldenburg, Germany; Jay LeBoeuf, Imagine Research, Inc. - San Francisco, CA, USA
In this paper we present several techniques to find the most significant frequencies in recorded audio tracks. These estimated frequencies could be used as a starting point for mixing engineers in the EQing process. In order to evaluate the results, we compare the detected frequencies with a list of reported salient frequencies from audio engineers. The results show that automatic detection is possible. Thus, one of the more boring tasks of a mixing engineer can be automated, which gives the mixing engineer more time to do the artistic part of the mixing process.
Convention Paper 7704 (Purchase now)