Let’s put the whole thing together today. How Noise, Distortion and signal level all fit together. How it all works.
Dynamic Range
All devices in audio – from a human voice to a mic to a preamp to a converter to a console to a power amp to a speaker to a human ear, all have a lower limit and an upper limit.
The lower limit is self-noise, the noise floor.
The upper limit is the distortion point, which is the spot that harmonic distortion becomes a big problem. By the way, the manufacturer decides what is unacceptable harmonic distortion.
So, that is the playing field in audio – from the Noise Floor to the Distortion Point. And we call that area the DYNAMIC RANGE.
Dynamic range can be huge. Your ear has a dynamic range of maybe 180 dB. You can hear from an ant picking its nose to something as loud as a gunshot about a foot from your head. Truly, though, if you’re listing to things ON PURPOSE and without HEARING PROTECTION louder than 112 dB you’re crazy. We will, of course, talk about dB later… much later…
Mics have dynamic ranges around 120 dB, which is about the same as a human ear on average. Mic preamps have dynamic ranges all over the place, from as high as 130 dB to 90 dB or even less. Digital audio recordings can have dynamic ranges well over 100 dB, depends on how they’re designed. Analog tape sorta sucks – lotssss of hisssss – dynamic range can be in the 70’s down to the 60’s even with noise reduction. Radio stations barely hit 50 dB of dynamic range.
How to set levels badly
Let’s learn how to be a shitty engineer quickly..
Our signal chain is a loud band (150 dB D/R), into a good mic (120 dB D/R), into an ok preamp (90 dB D/R) onto a tape track (70 dB D/R) and then out through a radio station (50 dB D/R).
Now, common sense would suggest you set the levels as high as possible. Especially when analog recording, the idea was to hit the tape very hard, making sure most of your signal was way above the noise floor, so the only time you’d hear hiss was when the song was very quiet, like at the beginning or the ending. ……….
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