Speaking in Academic Contexts
Rhetorical Functions in Academic Speaking: Narrating and reporting
Read the following texts:
The Evolution of Sound Recording
The history of recording sound stretches back to 1857. At that time, Leon Scott very much wanted to obtain a picture of what sound waves looked like. So he devised a method for recording the vibrations in the air. His device - he later patented as the Phonoautograph - used a large parabolic horn to channel incoming sound waves to a membrane covering the narrow end of the horn. He attached a bristle to the membrane by a lever and this traced a path in a revolving cylinder which was coated with lamp-black. As the membrane vibrated in response to sound waves, the bristle etched a pattern in the lamp-black that corresponded to the frequency of the sound. Although this was useful for gaining a view of what different sound waves looked like, the device could only record incoming waves - there was no provision for playing back the sound wave traces.
After studying the Phonoautograph, Thomas Edison modified the basic design in 1877 so that it could play back sounds. The sound quality was rather pitiful, but because he could actually do this others were encouraged to continue developing it. Edison's device used a grooved metal cylinder which was encased in tinfoil. When someone spoke into a horn, it concentrated the sound waves. At the apex of the horn, a thin membrane was attached to a needle and this transmitted the vibrations. The resulting waves were scored into the tinfoil as the needle moved up and down. This created a path which varied in depth. The cylinder in this device was rotated by means of a hand crank. Once the sound was recorded, the needle was returned to the beginning of the groove. Turning the hand crank caused the vibrations which had been captured in tinfoil to travel from the needle to the diaphragm and a crude replica of the human voice emerged from the horn.
Alexander Graham Bell took this invention a step further by replacing the foil-covered cylinder with one coated with wax. The needle cut a pattern that varied in depth onto the wax surface. For recording, Bell relied on a very sharp stylus and firm membrane. During playback, he switched to a dull stylus and a looser membrane so as not to destroy the original impressions. To reuse the cylinder, the wax could be shaved and smoothed. For the first time, sound recording could be accomplished on removable and reusable media. The process was further improved with the addition of an electric motor to replace the hand crank, so that recording and playback took place at uniform speeds. Recorded cylinders were then metal-plated to create a mould so that a number of copies of the original could be produced.
The technology was the beginning of a mini-industry. Phonograph parlours sprang up around the country in the late 1800s. In them, amazed visitors paid a nickel to hear voices muttering from these primitive playback devices.
They replaced the recording cylinder by a disc in 1888 when Emile Berliner devised a variation of this basic recording technique. Berliner's gramophone used a stylus travelling within a spiral groove on a flat disc. Sound waves caused the stylus to cut a pattern side to side within the groove. They could then reproduce the pattern on the disc using a metal mould and they could manufacture hundreds of recorded discs inexpensively from each mould. They made the disc itself out of metal covered with wax. After the stylus cut the pattern and removing the wax from its path, acid was used to etch the resulting waveform into the metal subsurface.
While the sound quality wasn't as good as that of the cylinders, the recording method was better suited to mass production. By the year 1910, people were selling discs and spring-wound players all over the world These featured recordings by some of the most popular singers of that era. When the vacuum tube amplifier was developed in 1912 by Lee de Forest, efforts were made to combine the phonograph and gramophone with amplified playback. This process took several more years.
During the same period that Edison, Bell, and Berliner were working on their sound recording devices, others were working on developing methods of magnetic recording of sound waves. Instead of imprinting the pattern os sound waves on a disc or cylinder, it is translated into a series of magnetic domains and we can store these on a variety of media. Oberlin Smith in 1888 claimed the first patent for such. Later, a man by the name of Poulson created a magnetic sound recorder that used steel tape as the recording medium. He exhibited his invention at the Paris Exhibition in 1900, calling his device a Telegraphone.
The radio broadcast industry was very interested in equipment that could store sound and immediately play it back. Since they could then repeat some broadcast material - such as newscasts - whenever they wanted. They could easily erase the tape and use it again. This was another major benefit. Work by DeStille in 1924 resulted in the Blattnerphone, and this impressed the British Broadcasting Company so much that they became involved in the development process. The Marconi Wireless Telegraph Company also jumped into the development effort, using steel-based magnetic tape that was initially biased to saturation. Rudimentary magnetic recorders were also produced, although the early versions required literally miles of steel tape to accommodate 20 or 30 minutes of recorded sound.
Cumbersome steel-based tapes gave way to plastic-based magnetic tape. It was possible to formulate the magnetic oxides coating plastic-based tape to change their recording and sound-storage properties. Undesirable characteristics such as print-through (the tendency of magnetic signals to leach through one layer of tape and affect adjacent layers) could be minimized through a choice of magnetic oxide.
We still use magnetic methods of recording in cassette recorders and reel-to-reel decks today, and we have made improvements in electronics, recording media, magnetic recording heads, and noise-reduction techniques which have maintained the viability of this recording method. However this method of recording is subject to certain limitations that have been largely overcome by digital recording techniques. Digital storage method have anabled signal-to-noise ratios of recorded sounds, among other factors, to be greatly improved.
After many years of development, digital recording gear has largely surpassed analogue, reel-to-reel, and magnetic tape recorders. Digital recording machines - such as the DAT, ADAT, RDAT, recordable mini-disc, portable studios with removable hard disk drive storage, and home computers have changed our perception of "high-fidelity" audio to startlingly clearer levels. In the digital realm, the signal-to-noise ratio is greatly improved over analogue equipment, meaning the dynamic representation of the music is greatly improved. The familiar hiss and tape noise common to analogue recording is conspicuously absent in digital recordings. This particular improvement in recording techniques ensures that the softest passages in a recorded musical work or speech will be as free of noise as the loudest levels of recorded audio. The recordist has a greater dynamic range to work with when using digital recording techniques, and fewer processing "tricks" are required to guarantee an effective sound recording.
Past tense is common.
Chronological order is also common, but when we are speaking about past events, it is necessary to be explicit about the order in which things happened. To make the order clear, we mention dates and time, and we also use various links and connectives.
In 1942, ...
During the 20th century, ...
Twenty five years ago, ...
Before he was offered a job as a lecturer,
he had finished his research.
Before this, .
For the previous X years, .
Prior to this, .
X years previously, .
. before which .
. prior to which .
he had finished his research, he was offered a job as a lecturer.
On finishing his research,
he was offered a job as a lecturer.
For the following X years, ...
X years later, ...
Following this, ...
Soon/Shortly/Immediately afterwards, ...
... following which ...
... after which ...
While he was doing his research,
he made an important discovery.
doing his research,
During his research,
During this period, .
Throughout this period, .
... during which ...
... throughout which ...