The decibel (dB) is a logarithmic unit of measurement used to measure various phenomena, such as sound intensity, electrical signals, or power ratios. The decibel scale expresses relative differences, which allows for easier comparison of large differences.
What does decibel mean?
dB expresses the ratio between two values on a logarithmic scale, based on the following general formula:
dB = 10 × log10 (P2 / P1)
P2: the value to be measured
P1: reference value
For sound intensity, the reference value is often the threshold of human hearing (0 dB), which is approximately 20 μPa (micropascals).
Characteristics of decibels
- Logarithmic scale: The dB scale is logarithmic, meaning that a 10 dB increase represents a 10-fold increase in sound intensity, and 20 dB represents a 100-fold increase.
- Relative unit of measurement: The decibel is a relative value, not an absolute value. For example, 0 dB does not mean that there is no sound, but that the intensity of the sound is the same as the given reference value.
- Sensitivity to human hearing: The sensitivity of the human ear is logarithmic, so the decibel scale is a good reflection of how we perceive loudness.
Noise reduction and insulation:
The effectiveness of noise-reducing materials or technologies is expressed in decibels.
Examples of decibel scale values
| dB value | Intensity | Example |
| 0dB | Hearing threshold | Sensing an air movement. |
| 30 dB | Quiet | Whispering in a quiet room. |
| 60 dB | Normal | Average conversation. |
| 90dB | Loud | Lawn mower or city traffic. |
| 120dB | Pain threshold | Concert or siren close-up. |
Why is the dB scale logarithmic?
- Wide range coverage: The logarithmic scale allows both extremely low and high intensities to be easily compared.
- Adapts to the nature of human hearing: The human ear perceives sounds in a non-linear manner: doubling the volume is not equivalent to doubling the physical intensity.
- Simplification: Use smaller, more manageable values instead of large numbers, e.g. 60 dB instead of 1,000,000.
Important notes
- Reference values: The dB scale always refers to a reference value. For example:
- In acoustics: 0 dB is the human hearing threshold.
- In electronics: 0 dB is usually 1 milliwatt (dBm).
- Non-linear perception: Human perception is nonlinear, so a 10 dB increase may be perceived as twice as loud, even though the physical intensity has increased 10 times.
Summary
The decibel (dB) is a universal, logarithmic unit of measurement widely used to measure sound intensity, electrical signals, and other ratios. The dB scale simplifies handling of large ranges of values and reflects the nature of human perception. Its knowledge and correct application are essential in acoustics, electronics, and other technical fields.