About Sound Recording : Description About Sound Recording.

Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording. Acoustic analog recording is achieved by a small microphone diaphragm that can detect changes in atmospheric pressure (acoustic sound waves) and record them as a graphic representation of the sound waves on a medium such as a phonograph (in which a stylus senses grooves on a record). In magnetic tape recording, the sound waves vibrate the microphone diaphragm and are converted into a varying electric current, which is then converted to a varying magnetic field by an electromagnet, which makes a representation of the sound as magnetized areas on a plastic tape with a magnetic coating on it. Analog sound reproduction is the reverse process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Electronically generated sound waves may also be recorded directly from devices such as an electric guitar pickup or a synthesizer, without the use of acoustics in the recording process other than the need for musicians to hear how well they are playing during recording sessions.

Digital recording and reproduction converts the analog sound signal picked up by the microphone to a digital form by a process of digitization, allowing it to be stored and transmitted by a wider variety of media. Digital recording stores audio as a series of binary numbers representing samples of the amplitude of the audio signal at equal time intervals, at a sample rate so fast that the human ear perceives the result as continuous sound. Digital recordings are considered higher quality than analog recordings not necessarily because they have higher fidelity (wider frequency response or dynamic range), but because the digital format can prevent much loss of quality found in analog recording due to noise and electromagnetic interference in playback, and mechanical deterioration or damage to the storage medium. A digital audio signal must be reconverted to analog form during playback before it is applied to a loudspeaker or earphones.

The automatic reproduction of music can be traced back as far as the 9th century, when the Banū Mūsā brothers invented "the earliest known mechanical musical instrument", in this case a hydropowered organ which played interchangeable cylinders automatically. According to Charles B. Fowler, this "cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century."[1] The Banu Musa also invented an automatic flute player which appears to have been the first programmable machine.[2]

In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder. Similar designs appeared in barrel organs (15th century), musical clocks (1598), barrel pianos (1805), and musical boxes (1815). All of these machines could play stored music, but they could not play arbitrary sounds, could not record a live performance, and were limited by the physical size of the medium. The first device that could record sound mechanically (but could not play it back) was the phonautograph, developed in 1857 by Parisian inventor Édouard-Léon Scott de Martinville. The earliest known recordings of the human voice were phonautograms also made in 1857. These earliest known recordings include a dramatic reading in French of Shakespeare's Othello and music played on a guitar and trumpet. The recordings consist of groups of wavy lines scratched by a stylus onto fragile paper that was blackened by the soot from an oil lamp [3]. One of his phonautograms of Au Clair de la Lune, a French folk song, was digitally converted to sound in 2008.[3]. While this is an interesting playback that sounds like a girl singing, the creator of this recording, Patrick Feaster of Indiana University in Bloomington, reports that phonautograms his team had previously transcribed, using a laser as a virtual stylus, had been played back at twice the actual speed. What sounded like a girl singing the French folksong was actually Léon Scott singing, Feaster concluded in May, 2009. Since the above recording was recovered, the same team have since recovered a recording of a 435-Hz tuning fork (at that time the French standard concert pitch for A' — now 440 Hz). The tuning fork is barely audible.

The player piano, first demonstrated in 1876, used a punched paper scroll that could store an arbitrarily long piece of music. This piano roll moved over a device known as the 'tracker bar', which first had 58 holes, was expanded to 65 and then was upgraded to 88 holes (generally, one for each piano key). When a perforation passed over the hole, the note sounded. Piano rolls were the first stored music medium that could be mass-produced, although the hardware to play them was much too expensive for personal use. Technology to record a live performance onto a piano roll was not developed until 1904. Piano rolls have been in continuous mass production since around 1898.[citation needed] A 1908 U.S. Supreme Court copyright case noted that, in 1902 alone, there were between 70,000 and 75,000 player pianos manufactured, and between 1,000,000 and 1,500,000 piano rolls produced.[4] The use of piano rolls began to decline in the 1920s although one type is still being made today. The fairground organ, developed in 1892, used a similar system of accordion-folded punched cardboard books.

Sound recording began as a mechanical process and remained so until the early 1920s (with the exception of the 1899 Telegraphone) when a string of groundbreaking inventions in the field of electronics revolutionised sound recording and the young recording industry. These included sound transducers such as microphones and loudspeakers, and various electronic devices such as the mixing desk, designed for the amplification and modification of electrical sound signals.

After the Edison phonograph itself, arguably the most significant advances in sound recording, were the electronic systems invented by two American scientists between 1900 and 1924. In 1906 Lee De Forest invented the "Audion" triode vacuum-tube, electronic valve, which could greatly amplify weak electrical signals, (one early use was to amplify long distance telephone in 1915) which became the basis of all subsequent electrical sound systems until the invention of the transistor. The valve was quickly followed by the invention of the Regenerative circuit, Super-Regenerative circuit and the Superheterodyne receiver circuit, all of which were invented and patented by the young electronics genius Edwin Armstrong between 1914 and 1922. Armstrong's inventions made higher fidelity electrical sound recording and reproduction a practical reality, facilitating the development of the electronic amplifier and many other devices; after 1925 these systems had become standard in the recording and radio industry.

While Armstrong published studies about the fundamental operation of the triode vacuum tube before World War I, inventors like Orlando R. Marsh and his Marsh Laboratories, as well as scientists at Bell Telephone Laboratories, achieved their own understanding about the triode and were utilizing the Audion as a repeater in weak telephone circuits. By 1925 it was possible to place a long distance telephone call with these repeaters between New York and San Francisco in 20 minutes, both parties being clearly heard. With this technical prowess, Joseph P. Maxfield and Henry C. Harrison from Bell Telephone Laboratories were skilled in using mechanical analogs of electrical circuits and applied these principles to sound recording and reproduction.[7] They were ready to demonstrate their results by 1924 using the Wente condenser microphone and the vacuum tube amplifier to drive the "rubber line" wax recorder to cut a master audio disc.[8]

Meanwhile, radio continued to develop. Armstrong's groundbreaking inventions (including FM radio) also made possible the broadcasting of long-range, high-quality radio transmissions of voice and music. The importance of Armstrong's Superheterodyne circuit cannot be over-estimated — it is the central component of almost all analog amplification and both analog and digital radio-frequency transmitter and receiver devices to this day.

Beginning during World War One, experiments were undertaken in the United States and Great Britain to reproduce among other things, the sound of a Submarine (u-boat) for training purposes. The acoustical recordings of that time proved entirely unable to reproduce the sounds, and other methods were actively sought. Radio had developed independently to this point, and now Bell Laboritories sought a marriage of the two disparate technologies, greater than the two separately. The first experiments were not very promising, but by 1920 greater sound fidelity was achieved using the electrical system than had ever been realized acoustically. One early recording made without fanfare or announcement was the dedication of the Tomb of the Unknown Soldier at Arlington Cemetery.

By early 1924 such dramatic progress had been made, that Bell Labs arranged a demonstration for the leading recording companies, the Victor Talking Machine Company, and the Columbia Phonograph Co. (Edison was left out due to their decreasing market share and a stubborn Thomas Edison). Columbia, always in financial straits, could not afford it, and Victor, essentially leaderless since the mental collapse of founder Eldridge Johnson, left the demonstration without comment. English Columbia, by then a separate company, got hold of a test pressing made by Pathé from these sessions, and realized the immediate and urgent need to have the new system. Bell was only offering its method to United States companies, and to circumvent this, Managing Director Louis Sterling of English Columbia, bought his once parent company, and signed up for electrical recording. Although they were contemplating a deal, Victor Talking Machine was apprised of the new Columbia deal, so they too quickly signed. Columbia made its first released electrical recordings on February 25, 1925, with Victor following a few weeks later. The two then agreed privately to "be quiet" until November 1925, by which time enough electrical repertory would be available.