All of us, except the deaf, hear a wide variety of sounds. We may hear music, we may hear a loud noise, we may hear cars or trucks or buses, we may hear other people talking to us or to others, or we may via the internet hear things being played like webinars or YouTube or Google Plus Hangouts- there’s no end to what we hear.
What Are Sounds?
Sound is the compression and rarefaction of air. If we hear a noise it is being compressed, and after the compression comes the rarefaction, again the compression, then the rarefaction. The waveform may be smooth, as a sine wave:
It may be something from an instrument, as this one is:
Or it may be noise:
Analog Audio And Digital Audio
Digital sounds are different. The analog to digital chip takes analog sounds and converts them into binary levels. This is timed, so that they are never smooth. Here is a diagram of the difference between analog audio and digital audio:
Notice that the smooth curve represents analog and the stair steps represent digital. So we’re going to hear clicks and pops when we listen to digital audio?
There’s a solution. Our hearing generally does not take in vibrations above 20,000 vibrations per second. That gives us plenty of room in terms of digital audio. At this point we have chips that function at 44,100 cycles per second, 48,000 cycles per second, 88,200 cycles per second, 96,000, and even ones that function at 192,000 cycles per second!
We can lower the sampling rate to 8,000 cycles per second, 16,000 cycles per second, 22050 cycles per second, 24,000 cycles per second, or 32,000 cycles per second. We do that when we don’t need a really accurate sense of what the sound is. When we need an accurate sense of what the sound is, we go for 44,100 cycles per second and up.
by Tom Jeffries, Chief Blazing Officer at Blaze Audio
Tom is a former professional musician who has been running companies that develop audio software for 33 years.