What is MP3?
MP3 is the popular term used to describe an audio file that uses the MP3 format for reducing the size of the audio file. An audio file in MP3 format doesn't contain all of the original audio signals but instead contains enough data so the human ear can listen to the audio file and not detect any missing sound.
Sound, Hearing and Music
Sounds such as voice dictation and music contain a substantial amount of information. When someone speaks or plays an instrument, a sound wave is created. The sound travels by creating pressure in the air, and the air transmits the pressure. That's why sounds are louder near their source and become lower in volume the further you are from the source. Air is a medium that can transmit vibrations and there are other mediums such as water or even steel, both of which are capable of transmitting sound waves. Eventually, the sound wave vibration might reach a human being.
When the vibration reaches our eardrums, we can hear the sound. Humans have listening devices, our ears, which convert the vibrations of sound waves into electrical signals that our brains can interpret. The eardrum is the part of the ear that converts these vibrations by moving as the vibrations in the air hit the eardrum. Stronger vibrations create louder sounds, and variations in the frequency of the vibration create what we know as pitch. One vibration per second is equal to one Hertz, the scientific term for frequency, Humans can generally hear sounds from 20 Hertz to 20,000 hertz in frequency. A person or instrument with a low pitch voice has a low frequency sound while a person with a high pitch voice has a high frequency sound.
The human ear is not an analog, not a digital device, meaning that it listens to sounds as a continuous wave, and the brain can interpret the information also. By the way, the brain's ability to interpret audio information is one reason people who have progressive hearing loss go so long without it being a problem or it being diagnosed. I learned this when I was fitted for my hearing aids (a result of natural aging and listening to way too much rock music when I was younger).
It's possible to record sounds as analog information using a microphone and a recording device such as a tape recorder or computer. When the audio information is in an analog format, it contains all of the recorded audio information and can be large for a computer file. Experts looked into ways to reduce the size of the file so the audio file would fit into less memory space and be smaller for transmitting over the Internet.
By making an audio file smaller, the file takes less time to travel over network connections like the Internet and takes up less space in memory on a computer or a portable device such as a smartphone. Some of the information in the file must be removed to make it smaller, and that's what “compression” is called.
Reducing the size of audio files
Audio information is a continuous wave and when it's recorded in an analog file the amplitude and frequency are recorded as a wave. To convert the file to a digital file, it;s necessary to take samples of the analog information and use a software program that codes the amplitude and frequency as zeros and ones. As part of the process of the conversion, samples of the audio wave are taken at specific intervals. It's a little bit like chopping up a tomato. By chopping the whole onion into pieces you still have the flavor of the onion in each piece, but each piece is separate and can be used individually or combined. The more slices, the more pieces there are to use.
Sampling an audio file is little bit like chopping up the onion. By chopping the audio file into pieces, each piece contains some of the audio information. When the pieces are combined together, the audio file sounds very much like the original. If you took out sample pieces of the onion, you'd have a portion of the onion to work with and you might have enough to create the flavor you were looking for. Use too much onion and you've got too much onion taste, use too little and you don't have enough flavor.
Audio sampling experts try to solve a similar problem. They try to take as little as possible to keep the file size small but use enough samples of the original audio file to preserve the sound. This is often referred to as the sampling rate, and here's were we get back around to MP3 instead of onions.
Audio coders
A compressed file has enough information to be usable but is smaller in size than the original file since it doesn't have ALL the information of the original. Analog audio files are compressed using a type of software program called a coder that samples the sound, keeps a portion of the audio information and removes what's not necessary to preserve the sound. An audio coder that takes out too much information would create a compressed file that might be very small, but it could also end up sounding different from the original audio sound if too much information was removed.
A good audio coder program will remove enough information to make the file small, but still contain enough information so that our ears will still hear the sound as it was intended. Programmers that create audio coder programs, also known as “codecs,” use their knowledge of human hearing and computers to create programs that sample the analog audio information and create a digital version of the audio in a smaller file size.
MP3
The MP3 format is the most commonly used industry standard audio coder format. It was developed by the Moving Picture Experts Group, an industry standard organization that has a mission to create and manage technology standards for the coded representation of digital audio, video, and related data. This is the organization that created the MP3 standard audio coder format. Most of the standards created by the Moving Pictures Expert Group are named MPEG and the MP3 format is part of the MPEG-1 standard and has evolved as technology has improved.
MPEG-1 Layer 3 is an audio coding format that provides excellent compression of music signals. There are MPEG-1 Layer 1 and Layer 2 audio coders, and Layer 1 isn't using much, but Layer 2 is still used for video broadcasting. The Layer 3 audio coder made portable audio electronics popular and widely available.
The MPEG-1 Layer 3 audio coder can compress a high-quality audio CD by a factor of 12, meaning that an MP3 song can fit in 1/12 the file size as the same song on a music CD disc and maintain a high audio quality, so the human ear doesn't hear a significant difference between the original audio file and the compressed MP3 file.
MP3 reduces the size of the audio file where it's practical to store in portable devices with smaller amounts of storage and to transmit or “stream” audio files using the Internet for music applications such as Apple Music, Spotify, and Pandora.
Today almost all audio devices playback the MP3 file format so in addition to your desktop or laptop computer, your smartphone, tablet, DVD player and car stereo can playback MP3 audio files.
To my way of thinking
MP3 made portable audio devices and listening possible and allows us to take our music with us wherever we go and enjoy it. If you're not using your smartphone for music, Apple users can obtain music from the iTunes store and Android from the Google Play store. Amazon offers MP3 files for purchase and apps like Pandora and Spotify make music available as long as you have an Internet connection.
Websites:
Moving Picture Experts Group - http://mpeg.chiariglione.org/
iTunes http://www.apple.com/itunes/
Google Play Music https://play.google.com/
Amazon Music http://www.amazon.com/MP3
Spotify https://www.spotify.com
Pandora http://www.pandora.com
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