Decibels are ratios that allows simple numbers to express values that would require many more digits. (used to describes pressure changes)
<aside> 🔊 Human Range of hearing
20uPa (micro Pascals) → 20Pa
</aside>
The decibel doesn’t use a linear scale, but a logarithmic one, which best describes human hearing.
Each step is the same size
Each step has the same proportion
Decibels are used as reference points for measuring volume
Guitars is the reference signal
In a mixer, 0 is the reference signal
| Abbreviation | Physical Unit | 0dB Reference |
|---|---|---|
| dBV | Voltage | 0 dB = 1V |
| dBu | Voltage | 0 dB = 0.775V |
| dBW | Electrical Power | 0 dB = 1 watt at (@) 50 ohms impedance (unless otherwise stated) |
| dBm | Electrical Power | 0 dB = 0.001 watts @ 600 ohms impedance |
| dB SPL | Sound Pressure | 0 dB = 0.00002 Pa (Human Threshold of Hearing) |
| dB VU (Volume Units) | Analog Audio Meter | 0 dB = +4dBu (1.228 volts RMS) |
| dB FS (Full Scale) | Digital | 0 dB = Maximum Value in a Fixed Point system |
0 dB SPL - represent the threshold of hearing (quietest humans can hear)
Therefore, +80dB SPL represent 80 dB more than the quietest sound humans can hear.
Graph of dB SPL
0 dB FS - represent the maximum use of bits in a digital system. Therefore, +1 dB FS creates clipping
A decibel is 1/10th of a bel (10dB = 1B)