FMX is the name of a commercially unsuccessful

noise reduction Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an u ...

system developed in the 1980s for

FM broadcasting FM broadcasting is a method of radio broadcasting that uses frequency modulation (FM) of the radio broadcast carrier wave. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to transmit high fidelity, high-f ...

in the United States.

FM stereo FM broadcasting is a method of radio broadcasting that uses frequency modulation (FM) of the radio broadcast carrier wave. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to transmit high-fidelity sound ...

broadcasting is known to incur up to a 23 dB

noise Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrat ...

penalty over that of

monophonic Monaural sound or monophonic sound (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or ''stereo'', which uses two separate audio channels to reproduce sou ...

FM broadcasting; this is due to the combination of the triangular FM noise

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

and the wider

baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into ...

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

occupied by the stereo

multiplex Multiplex may refer to: Science and technology * Multiplex communication, combining many signals into one transmission circuit or channel ** Multiplex (television), a group of digital television or radio channels that are combined for broadcast * ...

signal. Developed at the

CBS Technology Center CBS Laboratories or CBS Labs (later known as the CBS Technology Center or CTC) was the technology research and development organization of the CBS television network. Innovations developed at the labs included many groundbreaking broadcast, industr ...

, FMX was intended to improve this characteristic for listeners in the fringe areas where the noise penalty would be worst. This improvement was achieved by adding an amplitude-compressed version of the L−R (left-minus-right, or difference) signal

modulated Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information. The process encodes information in form of the modulation or message ...

in quadrature with the stereo

subcarrier A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio bro ...

, using a version of the CX noise-reduction system originally developed at

CBS CBS Broadcasting Inc., commonly shortened to CBS (an abbreviation of its original name, Columbia Broadcasting System), is an American commercial broadcast television and radio network serving as the flagship property of the CBS Entertainme ...

for

LP records The LP (from long playing or long play) is an analog sound storage medium, specifically a phonograph record format characterized by: a speed of rpm; a 12- or 10-inch (30- or 25-cm) diameter; use of the "microgroove" groove specification ...

. Upon his accession as Chairman of CBS, Laurence Tisch closed the CBS labs in 1986, whereupon the FMX

intellectual property Intellectual property (IP) is a category of property that includes intangible creations of the human intellect. There are many types of intellectual property, and some countries recognize more than others. The best-known types are patents, co ...

was spun off to an investment group, under the name Broadcast Technology Partners (BTP). With about 50 stations using the technology and perhaps another 50 committed, a controversy emerged in 1989 when

MIT The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

professor and

Bose Corporation Bose Corporation () is an American manufacturing company that predominantly sells audio equipment. The company was established by Amar Bose in 1964 and is based in Framingham, Massachusetts. It is best known for its Home audio, home audio syste ...

CEO

Amar Bose Amar Gopal Bose (November 2, 1929 – July 12, 2013) was an American entrepreneur and academic. An electrical engineer and sound engineer, he was a professor at the Massachusetts Institute of Technology for over 45 years. He was also the found ...

and Bose engineer William Short released a critical study, finding the system to have the potential to "seriously degrade the quality of stereo reception whether received by FMX equipment or not." According to the study, the heavy compression of the L−R audio caused

interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extra ...

in receivers under multipath conditions. A BTP spokesman rebutted the finding, saying that the Bose analysis exaggerated a "worst-case scenario", and actually employed "flawed mathematics" to attempt to prove their point. Perhaps not coincidentally, a

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling discl ...

application filed earlier by Bose disclosed an invention whose implementation was incompatible with the adoption of FMX, while another – filed by Bose and Short around the time of the release of the critical study – sought to improve the performance of FMX under multipath conditions. Despite industrial supporters in both the

broadcast Broadcasting is the data distribution, distribution of sound, audio audiovisual content to dispersed audiences via a electronic medium (communication), mass communications medium, typically one using the electromagnetic spectrum (radio waves), ...

and

consumer electronics Consumer electronics, also known as home electronics, are electronic devices intended for everyday household use. Consumer electronics include those used for entertainment, Communication, communications, and recreation. Historically, these prod ...

industries, the system never achieved a critical mass, and faded into obscurity. However, numerous related patents have since been applied for or granted, referencing the original FMX patents.Google Patents
/ref>

References

{{Reflist * U.S. Paten
4,485,483
''FM Stereophonic system incorporating companding of difference signal'', filed March 18, 1983, issued November 27, 1984.

''The Tech'' (MIT newspaper), February 28, 1989

''New York Times'', February 22, 1989. * "A theoretical and experimental study of noise and distortion in the reception of FM signals", Bose, A. G., and Short, W. R., ''IEEE Transactions on Broadcasting'', June 2001. Broadcasting Consumer electronics Radio noise reduction systems

See also

References