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Sound is produced from vibrating objects going through a medium. The vibrations, or WAVES , travel in all directions and reach your eardrums causing them to vibrate and the brain perceives that as SOUND .
Sound waves travel at different rates of speed and intensities . The frequency of a sound wave, measured in units of Hertz, is determined by the number of times it vibrates in one second. If a sound wave is vibrating at a very fast rate it produces a higher pitch and conversely, if it vibrates slowly, it will result in a low pitch. Hence, the vibrational frequency of sound determines the pitch of that sound.
Humans can hear frequencies between 20 and 20,000 vibrations per second – dogs can hear sounds even higher!!

INTENSITY: the amount of energy flowing in the sound waves depend on:
MEDIUM:
The substance (solid, water, gas) in which sound waves move is called the medium because it is the means through which sound is transmitted. In air, the forward movement of vibrating objects pushes molecules together, causing compression.
The opposite effect, known as rarefaction , is the reduction of a wave’s density.
LOUDNESS: volume is based on the strength of the sensation received by the eardrum and sent to the brain
AMPLITUDE:
The size or “height” of the sound wave, which we call the amplitude, indicates the strength of the signal and determines how loud a sound will be. Greater amplitude means that more energy accompanies the movement of the wave, thereby making it louder.
DISTANCE:
As the distance between a person and the source of the sound increases , the I & L decreases. Because sound waves move out from their source in all directions, the energy flowing in the sound waves spreads over a greater area and decreases the farther away the sound travels.

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Radio waves are a type of electromagnetic radiation that travel faster than the speed of light, and occur in nature when made by lightning or astronomical objects. Humans have harnessed their power in order to communicate sounds over long distances.
Depending on the length of the wave, different frequencies of radio can travel across the earth:
LONG waves tend to cover a part of the earth consistently, while SHORT waves can reflect off the ionosphere and travel around the world.
|| Lightning Radio || Sun Radio || Jupiter Radio ||

To transmit audio over the radio, the initial sound vibration is first picked up by a microphone, which then generates a weak electrical signal called a black wave. It then passes through an amplifier, where the amplitude (or power) is increased.
Meanwhile, an electronic circuit called an oscillator supplies a carrier wave (a high frequency electromagnetic wave that conveys the signal over the air), which is then combined with the black wave into a modulated carrier pulse of alternating current. The radio signal travels to the antenna, creating an electromagnetic field, or radio wave, that moves out in all directions, until it is picked up by a receiving antenna. In the last steps, the weak signal is amplified, cut in half (to remove the carrier wave) and finally, the audio signal is broadcast through the speakers.
Both AM & FM are analog transmission systems that process sounds into continuously varying patterns of electrical signals which resemble sound waves.
With AM radio, the amplitude (overall strength) of the signal is varied to incorporate sound information.
With FM , the frequency (number of times/second the current changes direction) of the carrier signal is varied, resulting in minimal noise from static. It has a longer range, and doesn’t get blocked by buildings.

1856 - 1943
In the early 1890s, Tesla’s In 1895, Marconi builds experiments exhibit transmission
1874 - 1937 a wireless telegraph system enabling ships of high frequency electricity. to communicate with the shore while they
He proposes that this could be a were out of visible range. In 1901, he means of telecommunication.
conducted the first successful transatlantic radio communication.
In 1902, the Poulsen - Arc radio transmitter is invented. It is one of the first technologies used to transmit AM radio.
In 1905, Lee De Forest’s invention of the vacuum tube diode leads to the invention of the Audion oscillator
(1912), which made inexpensive sound radio transmission possible and was responsible for the advent of radio broadcasting in 1920.
On Christmas Eve in 1906, Reginald Fessenden transmits the first radio audio broadcast: a violin playing Silent Night.
By 1912, every US ship is equipped with wireless radio. Just as radio became available to the public, America went to
War and the government assumed control of all the airwaves to bolster the war effort, thereby censoring it from public use. The advent of wireless communication technology drastically affected the army and navy and forever changed the way battles were fought.
In 1919, the government releases control of radio patents and the Radio Corporation of America is established. RCA brought about innovations in high power radio technology and formed the National Broadcasting Company
(NBC)
On November 2, 1920, station KDKA made the nations first commercial broadcast, reporting the results of election day before the newspapers were printed!

Throughout the 1920s, public radio stations begin popping up around the country - and by 1930, amateur radio operators begin experimenting with FM radio, making better quality broadcasts more accessible to the general population.
During the Great Depression, radio provided a necessary public service: free entertainment for the masses.
President Franklin D. Roosevelt recognized the power of the medium and began broadcasting his signature
Fireside Chats in order to clearly convey the policies he put into effect throughout his tenure in office.. The series of 30 radio addresses given by
FDR were the first modern media development that facilitated intimate
After the advent of Television, interest in radio decreases and and direct communication between the head of state and his citizens. stations primarily focus on music. However, with the invention of the transistor pocket radio, in 1954, people have the power to tune in anywhere!

In 1990, amateur radio experimenters began to use computers with audio cards to process radio signals, and the first digital transmissions began to be broadcast.
UNC - Chapel Hill station is the first to broadcast over the internet in 1994.
In 2000,
Pandora Radio is launched.
By 2004,
Podcasts become popular, forever changing the game.
By 2003, online internet radio is valued at
$49 million!
Sirius Satellite Radio is founded in 1999.