Linear amplitude is a direct measure of the magnitude or strength of a signal, such as a sound wave or an electrical signal, on a scale where the values represent the actual instantaneous displacement, pressure, or voltage. Unlike logarithmic scales like decibels (dB), linear amplitude changes proportionally with the physical quantity it represents.
Understanding Linear Amplitude and Decibels
Linear amplitude is often discussed in contrast to or in relation to the decibel scale, which is logarithmic. This logarithmic scale is useful because human perception of loudness is roughly logarithmic.
According to the provided reference:
- The linear amplitude 1 is assigned to 0 dB. This establishes a crucial reference point between the linear and decibel scales.
- A signal with a linear amplitude smaller than the reference (1) will have a negative amplitude in decibels.
- For example, a linear amplitude of 0.1 corresponds to -20 dB.
- A linear amplitude of 0.01 corresponds to -40 dB.
- This relationship continues as the linear amplitude decreases.
- A linear amplitude of zero (meaning no signal) is considered smaller than any positive or negative dB value, and it is assigned a dB level of negative infinity ($-\infty$ dB).
Comparing Linear Amplitude and Decibels
Here's a simple comparison:
| Feature | Linear Amplitude | Decibel (dB) Scale |
|---|---|---|
| Scale Type | Proportional (additive changes) | Logarithmic (multiplicative changes) |
| Reference | Often 1 corresponds to 0 dB | Reference level (e.g., 0 dB) is key |
| Representation | Direct physical quantity magnitude | Relative intensity or power level |
| Zero Value | Represents zero signal strength | Corresponds to $-\infty$ dB relative to ref |
Understanding linear amplitude is fundamental when dealing with signal processing, audio engineering, and various scientific fields where the actual magnitude of a waveform is critical before potentially converting it to a decibel representation for analysis or human perception modeling.
