| With audio signal retrieval of magnetic wire carriers as its main subject matter, this dissertation is a research on applied technology of audio production. The object of this research has been the remaining sound archive of Chinese traditional and folk music that was recorded by magnetic wire recording technology between the late 1940s and the early and mid 1950s.It has been over five decades since wire recording, which represents the early stage of the development of magnetic sound recording technology, passed into disuse. In light of the fact that the majority of this wire-recorded sound archive has failed to secure effective conservation and is therefore on the verge of extinction, the process of this research goes in strict compliance with The Safeguarding of the Audio Heritage: Ethics, Principles and Preservation Strategy (IASA-TC 03)(Version 3, Dec. 2005), laid down by the International Association of Sound and Audiovisual Archives Technical Committee. It tests the physical and chemical properties of the sample carriers, and then, on the basis of giving answers to the questions of"whether the sample carriers'physical and chemical properties have remained intact"and therefore"whether audio signal retrieval is possible", carries out an experimental research into the technique of retrieving wire-recorded audio signals.This dissertation consists of the following parts:Introduction: This part defines the subject matter, content and objectives of this research, discusses the relationship between the application of wire recording technology and ethnomusicology, gives an elaboration of the theoretical basis and some already-existing relevant experimental findings for this research, and outlines its plan, process and primary methodology, as well as the structure of the main body of this dissertation.Part 1: Through tracing the history of the development of magnetic wire recording technology as well as its application in the world, and through tracing the history and a few case studies of Chinese ethnomusicological field working and the development as well as the application of magnetic wire recording technology in China, this part discusses the particularity and inevitability of the historical connections between the rise and fall of magnetic wire recording technology on the one hand and China's remaining wire-recorded sound archive of Chinese traditional and folk music on the other. Thereupon, this part seeks to identify the material type of the carriers of China's remaining wire-recorded sound archive (four types being possible: carbon-steel wire,"420"stainless wire, 18-8 type stainless steel wire, and brass-plated wire with magnetic materials), and the brand & model of the wire recorder (the Webster-Chicago wire recorder model 80-1 and model 288, or the Chinese-made"Zhongsheng"brand wire recorder) of"the given historical format"that is required as the basis on which we retrieve the audio signals by objectively choosing the replay parameters (speed, playback equalization, track format etc.). Furthermore, through field investigations and studies, this part also helps obtain an understanding of the current situation of the remaining sound archive of Chinese traditional and folk music, which is the object of this research, plus its recording equipments in China.Part 2: Through a test analysis of the physical and chemical properties of the sample carriers of China's remaining wire-recorded sound archive of Chinese traditional and folk music, this part verifies the foundation for the retrieval and restoration of the audio signals --- the"integrity of the sample carriers'physical and chemical properties", and analyzes the diversity of the sample carriers'property of being magnetic which affects the wire's audio signal retrieval effect. The outcome of the test of the sample's major metal components shows, the material type of 90 per cent of the sample carriers of China's remaining wire-recorded sound archive of traditional and folk music is 18/8 type Chromium-Nickel stainless steel, whose chemical properties have remained intact till today. The parametric test of the sample's major physical property of being magnetic shows, the carriers'physical property of being magnetic has stayed in complete conformity to the conditions of ferromagnetic materials serving as the material for audio signal recording and storage. Therefore, it is safe to claim, these carriers have retained their original physical and chemical properties, and thus it is possible to retrieve audio signals from them.Part 3: In order to achieve the goal of"optimal signal retrieval from original carriers", this part focuses the experimental research of audio signal retrieval on"replay equipment"and"replay parameters", on which basis a series of experimental research in recording techniques are carried out, including the experimental research to explore the original wire recording equipments'restoration and audio measuring methods in which the author worked in a joint effort with experts of the Institute of Musicology of the University of Vienna, the Phonogrammarchiv and the Acoustics Research Institute of the Austrian Academy of Sciences, and Vienna University of Technology from September 2007 to September 2008. After the author returned to China, he managed to build up, through his independent efforts, an audio signal retrieval experiment platform that fits the characteristics of the wire recording carriers of China's remaining sound archive, carried out experiments to test and determine the replay frequency compensation characteristic that the audio signal retrieval platform needs, transplanted it into the above-said platform, and thereby broke the technological bottleneck that hinders the development of retrieval techniques of the remaining wire-recorded sound archive. According to the results of audio test and comparative analysis of the replay parameters, the major electro-acoustic technical performance of this platform far outdoes that of the original equipments'retrieval channel and that required for retrieving audio signals recorded by 18/8 type Chromium-Nickel stainless steel wires with a diameter of 0.004 inches and a design operating speed of 2 feet per second.Conclusion: This part retraces the outline of this research, summarizes three major achievements of this research as well as some relevant findings, objectively analyzes the limitations of this research, and makes some prospective points regarding questions in this area that merit further studying.This research has been conducted in the context that both relevant international standards and professional audio industrial standards concerning the preservation of wire-recorded sound archives are absent while the preservation practice of China's remaining sound archive of Chinese traditional and folk music urgently needs such standards. The major achievements of this research, including a test of the material type of the carriers of the sound archive, a technical appraisal of the integrity of the carriers'physical and chemical properties, the building of a audio signal retrieval platform, and the audio test and comparative analysis of replay performance parameters, help eliminate the key technological barriers, and fill a vacuum in domestic techniques and strategies for the technical appraisal and the audio signal retrieval of wire-recorded sound archive. The research boasts a high originality, and contributes to the preservation of magnetic wire-recorded historical audio documents and the restoration of sound archives with practical application value. In the meantime, the research also provides the prevailing international standards for sound archive protection with both case studies and practical operating methods and strategies concerning the preservation of wire-recorded sound archive.
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