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Project

Restoration of Old Ethiopian Audio Recordings

1. Introduction Since the invention of the cylinder phonograph by Thomas Edison in 1877 and it commercialization in 1887, humanity has used several storage media to record and store audio data. Vast amount of audio recording including entertainment, cultural, educational and research have been stored in these media and their current status is not well known. The stored data in these storage medium is faced with two important and unavoidable problems. First, the medium itself is deteriorating through natural aging and improper storage environment. Second over the years, recording formats and the hardware needed for recording/viewing/copying came and disappeared according to the evolution of technology, the market trends, and the decreasing availability of working equipment and experts. Such evolution increases the risk that archives are preserving unreadable and therefore useless materials. A survey conducted by Heritage Preservation Inc. in partnership with the U.S. Institute of Museum and Library Services of public institutions estimated that more than 17,000 such institutions hold sound recording collections for which they take a preservation responsibility. The survey estimated that there are around 46 million individual recordings in these institutions of which 44% of their audio collections were in “unknown condition”. Today, reliable estimates of the life expectancy of phonographic cylinders, disc recordings and magnetic tape are not available. The history of electronic media in Ethiopia starts with the first provisional radio station which was inaugurated in 1933 in a contract signed with an Italian Company. Two of the most important audio-visual libraries in Ethiopia are the Ethiopian Broadcasting Corporation (EBC) audio-video library and the Institute of Ethiopian Studies (IES) library of Addis Ababa University. EBC has been digitizing its audio and video library and has found out that some of the magnetic tape has been degraded. As a result of the degradation, the quality of some of the data has been lowered significantly and some of the data has been rendered unreadable. 2. PhD Thesis The degradation due to improper storage and unavoidable degradation due to inherent properties of the different storage media results in loss of information and quality. While the effect of some of these degradation factors is irreversible and results in complete or almost complete loss of information, some of them can be recovered in the digitization process or by using different digital signal processing techniques after the digitization process. Digital signal processing methods can be used on the digitized audio data for restoration or recovery. Restoration is used to increase the quality of the audio data while recovery is intended to recover lost data. Both require a thorough understanding of the models of the underlying audio data, storage media degradation process and noise present. With information on these models, different reconstruction techniques can be applied on the digitized data for restoration and recovery. This research focuses on using Digital Signal Processing Methods for restoration and recovery of audio recordings in Ethiopian Libraries. 3. Goals and Objectives The goal of the PhD research is divided into general objective and specific objective. 3.1. General Objective The general objective of this research is the restoration and recovery of old audio data in the context of Ethiopia. These audio data can be from Ethiopian audio libraries, such as EBC audio-video library or AAU IES library that have been degraded or from international libraries that have archived audio recordings of Ethiopian culture or speech by higher officials. 3.2. Specific Objective The specific objective of this research is the restoration and recovery of selected degraded media in order to set direction on how to approach the restoration and recovery problem in Ethiopia. The specific objectives of the PhD research are the following. • Review and compare the storage conditions of Ethiopian audio recordings with international standards and guidelines on how audio recordings should be stored; • Study and identify possible types of degradation affecting old stored audio data Addis Ababa Medial Library considering the storage conditions of; • Investigate the different noise and degradation models present in the stored media; • Restoration and/or recovery of selected sample degraded audio data that have reduced quality • Develop an application program that identifies different degradation present in an audio recording and try to restore the data. 4. Methodology The research will be implemented in the following four phases. • Problem identification and sample collection, • Data and degradation modeling, • Recovery vs. restoration identification and • Restoration and/or restoration implementation 4.1. Phase 1: Problem identification and sample collection In this phase, a review and comparison of the storage conditions of Ethiopian audio recordings with international standards and guidelines on how audio recordings should be stored will be conducted. In addition sample degraded audio recording will be collected from Ethiopian libraries and international libraries housing Ethiopian recordings. The collected samples will be analyzed to verify the digitization process used when converting the analogue tape to digital format. If inconsistencies are observed, the analogue tape will be re-digitized to obtain an improved data. 4.2. Phase 2: Data and degradation modeling Once the degraded samples have been collected, the samples will be analyzed to determine the underlying data model, degradation model and noise present in each data. These will help in developing compensation and reconstruction techniques to remove them. 4.3. Phase 3: Recovery vs. restoration identification Depending on the level of degradation present in the data, recovery or restoration may be required. As long as the audio is intelligible, restoration is the primary goal. Recovery is used only if the data is unintelligible. Such determination will be done on a case by case bases. 4.4. Phase 4: Restoration and/or Recovery implementation The main goal of restoration is to remove degradation present in the audio and increase the quality of the audio. There are several distinct types of degradation common in audio sources. These can be broadly classified into two groups: localized degradation and global degradation. Localized degradation are discontinuities in the waveform which affect only certain samples, including clicks, crackles, scratches, breakages and clipping. Global degradation affect all samples of the waveform and include background noise, wow and flutter and certain types of non-linear distortion.

Date:21 Sep 2017 →  20 Oct 2021
Keywords:Restoration, Old Audio Recordings
Disciplines:Sensors, biosensors and smart sensors, Other electrical and electronic engineering
Project type:PhD project