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HISTORY of

WGRL Kiya & Odetta 10/2014 What is ? Vibrations !

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 of a sound wave, measured in units of , 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 between 20 and 20,000 vibrations per second – dogs can hear even higher!! PRINCIPLES of SOUND MEDIUM: The substance (solid, water, gas) in which sound waves : move is called the medium because it is the means the amount of energy through which sound is transmitted. In air, the forward flowing in the sound waves movement of vibrating objects pushes molecules depend on: together, causing compression. The opposite effect, LOUDNESS: known as rarefaction, is the reduction of a wave’s volume is based on the density. strength of the sensation : The size or “height” of the sound wave, which we call the amplitude, received by the eardrum indicates the strength of the and determines how loud a and sent to the brain 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. M T O E R L E S G E R A C P O H D Y E What is a ? Radio waves are a type of electromagnetic radiation that travel faster than the speed of , and occur in nature when made by 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 and travel around the world. || Lightning Radio || Sun Radio || Jupiter Radio || AM vs FM To transmit audio over the radio, the initial sound vibration is first picked up by a , which then generates a weak electrical signal called a black wave. It then passes through an , where the amplitude (or power) is increased. Meanwhile, an electronic circuit called an oscillator supplies a (a electromagnetic wave that conveys the signal over the air), which is then combined with the black wave into a modulated carrier pulse of . The radio signal travels to the , creating an , 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 is broadcast through the speakers.

Both AM & FM are systems that process sounds into continuously varying patterns of electrical which resemble sound waves. With AM radio, the amplitude (overall strength) of the signal is varied to incorporate sound . With FM, the frequency (number of times/second the current changes direction) of the carrier signal is varied, resulting in minimal from static. It has a longer range, and doesn’t get blocked by buildings. Nikola BIRTH of RADIO Guglielmo 1856 - 1943 Marconi In the early 1890s, Tesla’s In 1895, Marconi builds 1874 - 1937 experiments exhibit transmission a telegraph system enabling ships of high frequency . to communicate with the shore while they He proposes that this could be a out of visible range. In 1901, he means of . conducted the first successful transatlantic radio .

In 1902, the Poulsen - Arc In 1905, ’s of the tube leads to the radio is invention of the oscillator invented. It is one of the (1912), which made inexpensive first used to sound radio transmission possible and transmit AM radio. was responsible for the advent of radio in 1920. On Christmas Eve in 1906, 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 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 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 in high power radio technology and formed the National Broadcasting Company (NBC) On , 1920, station KDKA made the nations first commercial broadcast, reporting the results of election day before the newspapers were printed! Golden Age of Radio

Throughout the 1920s, public radio stations begin popping up around the country - and by 1930, operators begin experimenting with FM radio, making better quality broadcasts more accessible to the general population.

During the , radio provided a necessary public service: free 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 development that facilitated intimate After the advent of , interest in radio decreases and and direct communication between stations primarily focus on . However, with the invention of the head of state and his citizens. the pocket radio, in 1954, people have the power to tune in anywhere! AGE:

In 1990, amateur radio experimenters began to use 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.

Sirius Radio is founded in 1999. In 2000, Pandora Radio is launched. By 2003, online By 2004, is valued at $49 million! become popular, In the fall of 2014, forever changing WGRL launches!!! the game.