AM radio in the context of "Radio frequency interference"

Broadcasting is the distribution of audio and audiovisual content to dispersed audiences via an electronic mass communications medium, typically using the electromagnetic spectrum (radio waves), in a one-to-many model. Broadcasting began with AM radio, which became popular around 1920 with the spread of vacuum tube radio transmitters and receivers. Before this, most implementations of electronic communication (early radio, telephone, and telegraph) were one-to-one, with the message intended for a single recipient. The term broadcasting evolved from its use as the agricultural method of sowing seeds in a field by casting them broadly about. It was later adopted for describing the widespread distribution of information by printed materials or by telegraph. Examples applying it to "one-to-many" radio transmissions of an individual station to multiple listeners appeared as early as 1898.

Over-the-air broadcasting is usually associated with radio and television, though more recently, both radio and television transmissions have begun to be distributed by cable (cable television). The receiving parties may include the general public or a relatively small subset; the point is that anyone with the appropriate receiving technology and equipment (e.g., a radio or television set) can receive the signal. The field of broadcasting includes both government-managed services such as public radio, community radio and public television, and private commercial radio and commercial television. The U.S. Code of Federal Regulations, title 47, part 97 defines broadcasting as "transmissions intended for reception by the general public, either direct or relayed". Private or two-way telecommunications transmissions do not qualify under this definition. For example, amateur ("ham") and citizens band (CB) radio operators are not allowed to broadcast. As defined, transmitting and broadcasting are not the same.

Garage rock (sometimes called garage punk or '60s punk) is a raw and energetic style of rock music that was mainly successful in the mid-1960s, most commonly in the United States and Canada, and has experienced a series of subsequent revivals. The style is characterized by basic chord structures played on electric guitars and other instruments, sometimes distorted through a fuzzbox, as well as often unsophisticated and occasionally aggressive lyrics and delivery. Its name derives from the perception that groups were often made up of young amateurs who rehearsed in the family garage, although many were professional.

In the US and Canada, surf rock—and later the Beatles and other beat groups of the British Invasion—motivated thousands of young people to form bands between 1963 and 1968. Hundreds of grass-roots acts produced regional hits, some of which gained national popularity, usually played on AM radio stations. With the advent of psychedelia, numerous garage bands incorporated exotic elements into the genre's primitive stylistic framework. After 1968, as more sophisticated forms of rock music came to dominate the marketplace, garage rock records largely disappeared from national and regional charts, and the movement faded. Other countries in the 1960s experienced similar rock movements that have sometimes been characterized as variants of garage rock.

Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves can only travel in a direct visual path from the source to the receiver without obstacles. Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted, refracted, reflected, or absorbed by the atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles.

In contrast to line-of-sight propagation, at low frequency (below approximately 3 MHz) due to diffraction, radio waves can travel as ground waves, which follow the contour of the Earth. This enables AM radio stations to transmit beyond the horizon. Additionally, frequencies in the shortwave bands between approximately 1 and 30 MHz, can be refracted back to Earth by the ionosphere, called skywave or "skip" propagation, thus giving radio transmissions in this range a potentially global reach.

High fidelity (hi-fi or, rarely, HiFi) is the high-quality reproduction of sound. It is popular with audiophiles and home audio enthusiasts. Ideally, high-fidelity equipment has inaudible noise and distortion, and a flat (neutral, uncolored) frequency response within the human hearing range.

High fidelity contrasts with the lower-quality lo-fi sound produced by inexpensive audio equipment, AM radio, or the inferior quality of sound reproduction that can be heard in recordings made until the late 1940s.

Vehicle audio is equipment installed in a car or other vehicle to provide in-car entertainment and information for the occupants. Such systems are popularly known as car stereos. Until the 1950s, it consisted of a simple AM radio. Additions since then have included FM radio (1952), 8-track tape players, Cassette decks, record players, CD players, DVD players, Blu-ray players, navigation systems, Bluetooth telephone integration and audio streaming, and smartphone controllers like CarPlay and Android Auto. Once controlled only from the dashboard with a few buttons, today they can be controlled by steering wheel controls and voice commands.

Initially implemented for listening to music and radio, vehicle audio is now part of car telematics, telecommunications, in-vehicle security, handsfree calling, navigation, and remote diagnostics systems. The same loudspeakers may also be used to minimize road and engine noise with active noise control, or they may be used to augment engine sounds, for example, making a small engine sound bigger. Vehicle audio systems have begun to move to digital platforms utilizing bus networks and optical cables for signal transfer rather than traditional analog cables.