Sound recording and reproduction

Frances Densmore recording Blackfoot chief Mountain Chief on a cylinder phonograph for the Bureau of American Ethnology (1916)

Sound recording and reproduction is an electrical, mechanical, electronic, or digital 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. Prior to the development of sound recording, there were mechanical systems for encoding and reproducing instrumental music, such as wind-up music boxes and, later, player pianos.

Acoustic analog recording is achieved by a microphone diaphragm that can detect and sense the changes in atmospheric pressure caused by acoustic sound waves and record them as a mechanical representation of the sound waves on a medium such as a phonograph record (in which a stylus cuts 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. Oscillations 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 via headphones.

Digital recording and reproduction converts the analog sound signal picked up by the microphone to a digital form by the process of digitization. This lets the audio data be stored and transmitted by a wider variety of media. Digital recording stores audio as a series of binary numbers (zeros and ones) representing samples of the amplitude of the audio signal at equal time intervals, at a sample rate high enough to convey all sounds capable of being heard. 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. Whereas successive copies of an analog recording tend to degrade in quality, as more noise is added, a digital audio recording can be reproduced endlessly with no degradation in sound quality. A digital audio signal must be reconverted to analog form during playback before it is amplified and connected to a loudspeaker to produce sound.

Pre-history

Long before sound was first recorded, music was recorded—first by written music notation, then also by mechanical devices (e.g., wind-up music boxes, in which a mechanism turns a spindle, which plucks metal tines, thus producing a melody). Automatic music reproduction traces back as far as the 9th century, when the Banū Mūsā brothers invented the earliest known mechanical musical instrument, in this case, a hydropowered (water-powered) organ that played interchangeable cylinders. 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][ unreliable source?] The Banu Musa brothers also invented an automatic flute player, which appears to have been the first programmable machine. [2] According to Fowler, the automata were a robot band that performed "...more than fifty facial and body actions during each musical selection." [1]

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 (ca.1800). A music box is an automatic musical instrument that produces sounds by the use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth (or lamellae) of a steel comb. They were developed from musical snuff boxes of the 18th century and called carillons à musique. Some of the more complex boxes also have a tiny drum and/or bells, in addition to the metal comb.

The fairground organ, developed in 1892, used a system of accordion-folded punched cardboard books. The player piano, first demonstrated in 1876, used a punched paper scroll that could store a long piece of music. The most sophisticated of the piano rolls were "hand-played", meaning that the roll represented the actual performance of an individual, not just a transcription of the sheet music. This technology to record a live performance onto a piano roll was not developed until 1904. Piano rolls were in continuous mass production from 1896 to 2008. [3] [4] 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. [5] The use of piano rolls began to decline in the 1920s although one type is still being made today.

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