when was the digital recording device invented?
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digital sound recording, method of preserving sound in which audio signals are transformed into a series of pulses that correspond to patterns of binary digits (i.e., 0’s and 1’s) and are recorded as such on the surface of a magnetic tape or optical disc.
A digital system samples a sound’s wave form, or value, several thousand times a second and assigns numerical values in the form of binary digits to its amplitude at any given instant. A typical digital recording system is equipped with an analog-to-digital converter that transforms two channels of continuous audio signals into digital information, which is then recorded by a high-speed tape or disc machine.
The system uses a digital-to-analog converter that reads the encoded information from the recording medium and changes it back into audio signals that can be used by the amplifier of a conventional stereo sound system.
In addition, many digital recording systems are designed to detect and eliminate interfering signals. In the 1980s digital compact disc recordings became available that were played by using a laser beam to optically scan digital information encoded on the disc’s surface. In the late 1980s digital audio tape (DAT) recorders using magnetic tape cassettes became available for audio reproduction and recording.
The early 1990s saw the introduction of digital compact cassette (DCC) recorders, which were similar to DAT recorders but could play the older analog tape cassettes in addition to similarly shaped digital cassettes. See also sound recording.
microphone
, device for converting acoustic power into electric power that has essentially similar wave characteristics. While those on telephone transmitters comprise the largest class of microphones, the term in modern usage is applied mostly to other varieties.
Apart from telephone transmitters, microphones are most widely applied in hearing aids, sound-recording systems (principally magnetic and digital tape recorders), dictating machines, and public-address systems. Microphones are extensively used in communications systems, radio or wire, to provide better response quality than with conventional telephone transmitters, or for hands-free operation.
In a microphone, sound waves (sound-pressure variations in the air) are converted into corresponding variations in electric current in two operations that take place almost simultaneously. In the first, the sound wave impinges on a slightly flexible surface (diaphragm), causing it to move to and fro in a manner corresponding to the movement of the air particles.
Depending on the type of microphone, displacement of the diaphragm may cause variations in the resistance of a carbon contact (carbon microphone), in electrostatic capacitance (condenser microphone), in the motion of a coil (dynamic microphone) or conductor (ribbon microphone) in a magnetic field, or in the twisting or bending of a piezoelectric crystal (crystal microphone). In each case, motion of the diaphragm produces a variation in the electric output.
History of Digital Recording
100 years was the time distance between the discoveries of first sound recording device and implementation of digital recording. During those 100 years, constant technological advancements and endless innovations from scientist and technicians enabled the creations of several distinct waves of mechanical sound capturing, processing and reproducing.
From simple tin foil and wax cylinders who were carefully engraved with the sound information gathered by recording diaphragm, widely popular disc based gramophones who swept over the world, to the cassette tapes who enabled listeners to enjoy multichannel sounds, industry of sound recording received gigantic step forward with the rise of the computers and digital audio.
Digital recording
represent storing information about sounds not in a physical way like on gramophone discs or as magnetic signatures as with magnetic tapes, but as a series of discrete numbers that represent changes in air pressure trough time. This new way of storing data finally enabled technicians and scientist to preserve sound in unrivaled quality (which was unobtainable with previous technologies, especially low levels of noise and distortion), and enable permanent preservation of sound in its original state no matter how many times the sound was played.
Sound is transferred into digital form by analyzing sound wave thousand times per second, and assigning each sample with unique binary signature.
First digital recordings
were saved on magnetic tapes and were demonstrated to the public in late 60s Japan. However, it was 1977 that saw the release of first commercially available digital audio recorder – Sony PCM-1.
It converted analog audio into digital and stored it on VHS tapes that would later be used in digital mastering, but commercial music continued to be sold on magnetic tapes and vinyl. That all started to change in late 1970s when Sony and Panasonic started showcasing compact disc, a true digital medium that had the capacity to hold up to 150 minutes of high quality audio.
Saved by Betamax
Two years after joining Sony as chief of the Audio Technology Center, Nakajima together with Jun Takayama and Hiroyuki Suzukawa began work on the development of digital audio.
The building in which they worked was some distance from the Sony head office in which Ibuka worked, making it difficult for Ibuka to see what Nakajima and his colleagues were working on.
The distance between the two buildings was enough to allow Nakajima to push ahead freely with his endeavors, unhindered by constant inspection. Nakajima forged on, always mindful of the motto, “Continuity is strength.”
To code an analog signal or to establish a digital modulation system, Nakajima continued to work with the PCM (Pulse Code Modulation) that he had used during his time at NHK. This system was based on a concept introduced in 1939 and was the same one used for computers, long-distance telephone transmission and broadcasts to Earth from Apollo space-crafts.
The amount of tape space taken up by digital audio recording is about one hundred times that of an analog audio recording or the same amount of space on a tape used by a broadcast-use VTR. Therefore, conventional analog audio devices could not be used because the tape could not record enough. When a mechanism is made from scratch, this machinery becomes unavoidably large.
The Approval of Maestro Herbert von Karajan
It is difficult to know exactly how a product will be used until it has been launched. Depending on where and by whom a product is used, the product will either function well or encounter difficulty. Those who design a product have little influence on its success once launched.
For example, there were a number of complaints from people, who used the PCM-1 in combination with various audio units, including FM tuners. They found that it produced an unpleasant electronic humming noise. An increase in dynamic range caused the machine to pick up noise unless the unit was operated in a quiet, soundproof room.
This gave rise to complaints of poor sound quality. With any new product, problems that cannot be foreseen in the laboratory are bound to occur, and Nakajima received a continuous stream of complaints.
Eventually, Nakajima and his colleagues moved to stem the tide of criticism, sorting through and analyzing the various grievances. A large number of the problems had occurred because R&D efforts had not been sufficiently thorough because of the haste to create a finished product within one year.
Also, the group discovered that the operating instructions supplied with the machines were not sufficient and resulted in misuse.
The Age of the Optical Disc Follows
system
From the early stages of the PCM-1 development, Sony had been looking for a way to record and play back sound using a digital audio disc. In 1975, Sony put the Betamax VCR on the market. At the same time, Sony had been working to market an optical videodisc (laser disc) which was developed by Philips.
In spring 1976, Doi and his colleagues delivered a prototype of the PCM-1 to Miyaoka and his team and asked them to make a disc, which could record digital audio. This disc was probably the first digital audio disc prototype in the world.
The type of signals recorded by the Betamax and the video disc were the same, meaning that the PCM-1, which had been developed as an adapter for the Betamax, could also be used as an adapter for the video disc player.
At this time, Doi’s plan was to connect the videodisc player to the PCM-1, thus creating a digital audio disc.
