Difference between revisions of "DIGITAL SOUND"
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=== Vinyl Belts ===
=== Vinyl Belts ===
1950-1980s The Dictabelt machine used these colorful recording devices for consumers and corporations. The flexible vinyl
1950-1980s The Dictabelt machine used these colorful recording devices for consumers and corporations. The flexible vinyl maintained their playable integrity better than earlier recording mediums if they were not hardened with heat.
=== Optical Disks ===
=== Optical Disks ===
Revision as of 22:08, 18 March 2014
Many genealogists will come in contact with an outdated audio format. Understanding how to convert these audio recordings to digital sound is essential for preservation. Whether creating new audio recordings, or preserving audio history, this class will educate genealogists about choosing proper audio recorders, transfer methods, and file formats to maximize digital sound quality.
- 1 Introduction
- 2 The History of Sound
- 3 Historic Events for Sound Recordings
- 4 Genealogical Applications
- 5 Digital Sound File Extensions
- 6 Purchasing A Digital Recorder
- 7 Summary
Digital Audio has emerged as a means for genealogists to easily protect, share, and distribute historical audio files. It provides a simple and easy way to transfer information from analog or vintage audio formats into an editable, shareable format to provide longevity for deteriorating audio files.
Analog is a technology where signals are sent from one device to another, like TV signals, cell phone signals, and signals used to magnetically rearrange particles on a piece of magnetic tape to re-create sound. Analog tape is capable of capturing the frequency and range of the human voice.
Professional grade analog tape recorders can provide a high quality audio recording; however, analog tapes are fragile. Analog recordings must be digitized before computer-assisted editing or analysis can occur.
The History of Sound
Understanding what sound recordings may exist will help genealogists locate audio recordings for an ancestor.
1877-1930 Thomas Edison’s earliest phonograph used tin foil cylinders for dictation recording with no significant consumer market. Wax and fibrous materials coated in shellac or celluloid were used from 1886-1930. Cylinders had a capacity of 2-9 minutes.
1887-present. Invented by Emile Berliner, these were made with wax, hard rubber, and later with shellac, condensate plastic, acetate, or celluloid coated over fibrous cores. With the invention of electric records in 1924, acoustic records and recorders diminished in use.
Records have a storage capacity of 3-30 minutes per side. Vintage and home recorded records are easily destroyed with water or by playing them on modern turntables.
1889-1952 Magnetic wire was invented by Vlademar Poulsen. Magnetic wire was used most predominantly by Americans in the mid-1900s (1940s on) by consumers and for World War II decoding. Consumer wire recorders were often very small and portable.
1935 AEG/Telefunken introduced the first reel-to-reel magnetic tape recorder in Germany. In 1937 steel tape recorders were developed by Bell Labs and the Brush Development Company, lengthening the play/record time, but weakening the sound quality. In 1946, German magnetic tape recorders were brought to the United States and copied. In 1948, A.M. Polikoff (AMPEX) sold magnetic tape recorders for U.S. commercial use.
Between 1960-1964, compact tapes and recorders were developed and sold in the U.S. and Europe, including 4-track, and 8-track formats, and the more popular compact analog cassette tape that is still used today. In 1990 the digital audio recorder was introduced, using magnetic compact cassette tape as the storage medium.
1950-1980s The Dictabelt machine used these colorful recording devices for consumers and corporations. Recording time was usually 15mins. A blunt needle embossed the sound waves onto the belt. The flexible vinyl belts maintained their playable integrity better than earlier recording mediums if they were not hardened with heat.
1982 The Compact CD was introduced in Japan. In 1996 Digital Versatile Discs (DVDs) were developed, increasing storage capacity to 4.7 Gigabytes per side. Recordable CD-Rs became a part of PCs by 1999. From 2000-2001, DVD recorders were released and developed into data and media storage devices for computers.
Solid State Devices
2001 Apple introduced iPods to consumers as a device to store and hear a large capacity of music or audio recordings. Solid state means that no moveable parts are included in the storage process, but that all information is stored in semi-conducting components or devices such as memory chips.
Historic Events for Sound Recordings
1897 Many Americans are able to afford purchasing a ‘talking machine.’
1914-18 U.S. Sound manufacturers jump from 18-166 in number, increasing availability.
1930s Disk Cutters are available in department stores and other public areas, allowing the consumer who cannot afford a home record cutter to create recordings of their voices.
1940s Wire recorders were used to record transmitted sound to break codes during the War. The use of wire recorders during the war increases consumer interest.
1957 Max Matthews of Bell Telephone Laboratories first develops the process to digitally code sound using a computer.
1950-74 The race to put man in space created a greater need for digital devices that were self-contained and compact. PDAs, microprocessors, personal computers, microchips, and the Internet are developed.
Digital sound applies to every genealogist. Below are some uses for digital sound that apply to the beginner genealogist or the professional researcher:
1. Recording new oral histories.
2. Preserving pre-recorded oral histories.
3. Transferring sound files from vintage formats to digital.
4. Adding music or narration to family movies or digital slide shows.
5. Recording information for speech-to-text transfer.
6. For dictation or easy distribution of conferences and meetings.
Digital Sound File Extensions
Understanding digital sound file extensions is very important to determine the quality of the sound file. It is important for a user to understand that different sound files are different in quality.
What is a file extension?
File extensions are the three or four letters following a period after the file name. The most common type of sound file extensions are: AIF, AU, MID, MIDI, MP3, RA, RAM, RM, WMA, and WAV. File extensions help the user understand what type of program can read that extension.
File extensions may compress a sound recording. Some sound files are raw, meaning that they are a true, full-sized copy of the audio, and some sound files are compressed. Compression means that the file is made smaller, much like ‘zipping’ a file to make it smaller in order to e-mail it to someone.
Lossless and Lossy
Compression can happen in two different ways: lossy and lossless. Like the name indicates, lossy means that when sound file is compressed, or made smaller, the file loses some of its original quality. Lossless is a compression form that keeps all of the quality of the original audio.
Which File Extension?
Each file format is different.
· AIFF, AU, and WAV are raw, or uncompressed audio files. They may take up space, but maintain the quality of the original recording.
· FLAC, APE, WV, lossless RA, and lossless WMA are all lossless. They maintain the quality and don’t take up as much space.
· MP3, lossy WMA, lossy RA, and AAC are all lossy formats. They don’t take up much space, but are lower quality recordings.
When creating a new digital sound file, or saving it to the computer for the first time, the user often has the option to choose which file extension in which to save it. Just changing a sound file extension in the name does not change the file type. The computer must help the user assign this extension, or the file must be run through a converter.
Genealogists interested in adding sound clips to Personal Ancestral File need to convert a sound file to WAV. Other genealogy database programs may also allow for sound file and multi-media additions.
Purchasing A Digital Recorder
Digital recorders differ in recording medium and format. Preferred PCM (Pulse Code Modulation format) means that the file is initially changed from analog to digital through measuring portions of the sound and transferring the sound to zeros and ones. This is gathered in raw form rather than compressed. PCM is usually saved as a WAV or AIFF file. Digital recorders that save in MP3 or WMA format are compressed and lossy. WAV format is a raw file. The raw file takes more space than the compressed file, lowering the recording time. Many consumers do not understand this when purchasing a digital recorder.
High quality sound measurements
Quality CDs are recorded at 44,100 Hz and 16 bit ‘word’ length. The bit refers to the number of computer numbers assigned to describe a length of sound, much like the number of words used to describe a picture. The higher the kHz and bit rate, the higher the quality of the digital sound. 1 kHz = 1000 Hz.
Consumer recorders usually list the number of hours they can hold. This refers to the size of the memory and the file compression rate. A higher number of hours may mean that the files are compressed, or smaller. Digital recorders are considered ‘high quality’ at 16 kHz and 8-16 bit resolution.
A digital recorder should have the following physical features to make sure that it is user-friendly and will be useable for the genealogist.
· Adequate memory: The number of hours is not always a reflection of larger memory. The files may be compressed.
· Expandable memory: Most digital recorders only have internal memory that cannot be removed, or expanded, but some come with card slots to create more room. Find out if it is possible to record directly onto the memory card if this is a desired option.
· Computer Connectivity: Some less expensive digital recorders cannot be connected to a computer with USB cables. This means that the files are not transferable to the computer. For genealogists, this is a wasted device.
· Usability: Check to see if the play, power, rewind, fast forward and stop buttons are clearly visible. More visible buttons means less use of a digital menu to find features.
Digital sound applies to everyone. Learning how to properly work with digital sound will help preserve important historical media that would otherwise easily deteriorate and be lost to future generations.