HOW DOES A VOCODER WORK SERIES

To encode speech, the vocoder measures to see how much energy there is within a set of frequency bands, and stores the readings as a list of numbers. HereвЂ™s a vocoder built for Kraftwerk in the 1970s: The name is short for Voice Operated reCOrDER. The earliest version was developed by Homer Dudley, a research physicist at Bell Laboratories in New Jersey. Now, at last, youвЂ™re ready to understand what the vocoder is and how it works. Warmer colors mean the phasors are bigger, and cooler colors mean the phasors are smaller. The colors show amplitude, also known as loudness. Think of the lower frequencies as phasors spinning around more slowly, and the higher frequencies as phasors spinning around faster. The vertical axis represents frequency, what musicians call pitch. This plot of the Fourier transform is called a spectrogram. This is vastly more efficient and technologically tractable than trying to store a billion individual voltage readings.Д¬lick the image below to do a Fourier transform of your voiceВ using the Chrome Music Lab.

If you make a list of the phasor magnitudes, you get a very nice and compact numerical expression of your super complicated waveform. вЂњPhasor magnitudesвЂќ is the daunting math term for the size of the clocks. This is a difficult idea to express verbally, but it makes more sense if you play with Jack SchaedlerвЂ™s cool interactive. If you connect a bunch of phasors together, together they can draw any crazy sinusoid you want. The sci-fi-sounding term for one of these clock hands is a phasor. You can also represent sine waves as the path swept out by a clock hand going around and around. HereвЂ™s an example, a square wave broken down into a sum of sines: Breaking down a waveform into its simple sine wave components is called a Fourier transform. ThatвЂ™s helpful, because sine waves are easy to express and manipulate mathematically. Jean-Baptiste Joseph FourierВ gave us some super useful ways to analyze and express such signals mathematically.ДЇourier realized that you can express any sinusoidal waveform, no matter how complicated, as the sum of a bunch of simple sine waves. That adds up to five megabytes of data per minute of audio, which is too much to transmit even in 2017, much less with 1930s technology.ДЇortunately, you can use math to make the problem more tractable. The standard for compact disks calls for you to take 44,100 readings per second, and each reading takes up two bytes of memory. The problem is that you need a whole lot of numbers to capture the sound accurately.

HOW DOES A VOCODER WORK SERIES

You can store a sound as a series of numbers by taking readings of the voltage coming off the microphone. In the 1930s, Bell Labs began researching ways to digitize voice transmissions. You can also use microphones to convert air pressure fluctuations into electrical current fluctuations, which you can then transmit, amplify, record, and so on. Your ear is a very precise tool for measuring momentary fluctuations in air pressure, and itвЂ™s able to decode these changes as sound. The takeaway is this: as things in the world vibrate, they make the air pressure fluctuate. I wrote my own basic explanation of what sound is and how you digitize it. Jack Schaedler made this delightful interactive that will get you started. To understand the vocoder, first you have to know a bit about how sound works. Also, the vocoder gave rise to Auto-Tune, which, love it or hate it, is the defining sound of contemporary popular music. You may be surprised to learn that you use a vocoder every time you talk on your cell phone. HereвЂ™s Huston Singletary demonstrating the vocoder in Ableton Live. Here I explain what it is, how it works, and why you should care.Д¬asual music listeners know the vocoder best as a way to make the robot voice effect that Daft Punk uses all the time. The vocoder is one of those mysterious technologies thatвЂ™s far more widely used than understood.

How does a vocoder work