Audio Recording, Mechanical

Mechanical recording and reproduction of sound on disk followed ten years after Thomas Edison’s invention of these techniques on cylinder. In 1887, Emile Berliner filed for and received his patent on the gramophone recording and reproduction system. Shortly after 1900, technical developments and commercial agreements in the U. S. established disk records as an independent medium.

By 1910 they dominated global markets for recorded sound. Mechanical recording remained the technique of choice for the storage of sound for the next 40 to 50 years, and disk ‘‘records’’ continued to be a significant medium for consumers of music and other sounds into the 1980s.

Disk recording requires that sound waves be converted into mechanical force that makes a stylus engrave or otherwise reproduce the waves as a spiral groove on a spinning disk composed of some pliant material. To play back the sound wave on the same disk or on a copy stamped from a matrix, a stylus tracks the groove representing the wave.

This energy is then converted into mechanical force that drives one or more loudspeakers. The development of this technology during the twentieth century is one of incremental improvements punctuated by revolutionary changes in technique and materials.

Recording changed very little in form from 1901, when Eldridge Johnson’s synthesis of earlier inventors’ work with his own insights became the Victor Talking Machine Company, to 1925. Performers directed their voices or instruments at a horn that channeled sound waves to a diaphragm. The membrane was linked to a stylus driven by a feed screw along the radius of a metallic wax disk spinning between 74 and 82 revolutions per minute (rpm). Miniature flyball governors controlled the speed of the turntable so that the record was rotated at a constant speed.

The stylus cut the wax vertically (‘‘hill and dale’’) or laterally.

Once recorded, the disk was electroplated, creating a master from which records or secondary stampers could be made. Victor and its partner companies made records from mineral powder, shellac, and carbon black; Columbia Records either copied Victor’s technique or used pure shellac laminated over a paper core.

Edison had also moved from cylinders to records, and the ‘‘Diamond Disks’’ made from 1912 to 1929 used a wood flour base coated with a varnish called condensite. Consumers played records on spring- wound gramophones or talking machines where the process for recording was reversed through steel stylus, diaphragm, tone arm, and horn.

Improvements in diaphragms, styluses, room acoustics, and horn placement enabled increases in the signal-to-noise ratio and frequency range while reducing distortion in the reproduced sound. By the late 1910s, companies had standardized record diameters at 10 and 12 inches (254 and 305 mm), playing three and five minutes respectively, and progressed from recording individual performers of selected instruments to symphony orchestras.

The revolution of electronic recording with microphones and amplifiers took place after World War I. Joseph Maxfield and Henry Harrison of Bell Telephone Laboratories applied scientific techniques of research and development to extend the undistorted frequency range of recording from 220-4,000 Hz to 100-6,000 Hz, and to raise the signal-noise ratio to 32 dB. To meet competition from wireless broadcasting, record companies began licensing the Bell system in 1925.

Electronic recording stimulated systems improvements and standard speeds in reproduction. For the consumer and home market, the ‘‘78’’ record (78.26 rpm) was standard, and the broadcast and film industries used 33.33 rpm. Electronic amplification reduced the need for abrasive fillers that resisted the stylus pressure of mechanical reproduction, while the higher frequencies aggravated the sound of needle ‘‘scratch’’ generated at the interface of stylus and the record groove.

Despite the global economic depression, the 1930s were a fertile period for recording innovations. Alan D. Blumlein of Electric & Musical Industries and Arthur C. Keller of Bell Laboratories invented single-groove stereophonic recording systems, for which their corporations could not find markets. Record companies began recording on metal disks coated with man-made lacquers and stamping disks of man-made plastics.

Researchers learned more about acoustics, recording and plating techniques, and the science of the stylus-groove interface. In the latter field, Frederic V. Hunt and John Pierce of Harvard University developed a stylus and pickup ten times lighter than contemporary devices.

Hunt and Pierce also anticipated the advantages of the narrower microgrooves that RCA Victor engineers began applying in 1939 to their vinyl chloride-vinyl acetate copolymer, 7 inch, 45 rpm, record system. World War II and rising sales deferred replacement of the 78 until 1949, a year after Columbia Records introduced vinyl compound, 10- and 12-inch, 33.33 rpm long-playing records (LPs) using RCA’s microgrooves. The jukebox industry quickly adopted the 45, which survived to the end of the century in the pop singles market. The new records gave less distorted sound reproduction up to 10,000 Hz with a 60 dB signal-noise ratio.

At the time, all music was monophonically recorded and reproduced. The postwar growth of magnetic recording techniques enabled multitrack recording, which led to the international standard for stereophonic disk reproduction in 1958. During this time, engineers refined the art of microphone placement and recording techniques to produce what has become known as the ‘‘Golden Age’’ of recording.

Efforts to put four channels on disk in the early 1970s failed because of the lack of a standard and the rise of magnetic-tape cassettes. Cassettes surpassed LP sales in the United States in the late 1970s, and this was followed by the introduction of the compact disk (CD) ten years later. Major labels abandoned vinyl records in 1990, although some production continued in the U.K. and on independent record labels.

The main refuge for disk records became audiophile and reissue pressings and discotheques, where disk jockeys had been playing extended versions of popular songs on 12-inch records since the early 1970s. The playing time of 5 to 12 minutes permitted increased amplitude of the groove and a concomitant rise in dynamic range. Ironically, in the middle of the digital revolution of CDs, the cult success of vinyl disks forced the major companies to continue pressing LPs and 45s for top performers through the end of the century.