Sound Pressure to Decibel Converter
| Measure | Value |
|---|
Information:
Formula: dB SPL = 20 * log10(p / p0)
Where p is the measured sound pressure and p0 is the reference sound pressure (20 μPa in air).
0 dB SPL is the threshold of human hearing.
Here's a comprehensive table with all the essential information about converting sound pressure to decibels:
| Aspect | Information |
|---|---|
| Basic Formula | dB SPL = 20 * log10(p / p0) |
| Reference Pressure (p0) | 20 μPa (micropascals) in air |
| 1 μPa in water | |
| Threshold of Hearing | 0 dB SPL (at 1 kHz) |
| Threshold of Pain | ~120-140 dB SPL |
Key Conversion Points:
| Sound Pressure (Pa) | Decibels (dB SPL) |
|---|---|
| 20 μPa (2 * 10^-5) | 0 dB |
| 1 Pa | 94 dB |
| 10 Pa | 114 dB |
| 100 Pa | 134 dB |
Important Notes:
- The decibel scale is logarithmic, not linear.
- Every 6 dB increase represents a doubling of sound pressure.
- Every 20 dB increase represents a 10-fold increase in sound pressure.
Common Sound Levels:
| Source | Approximate dB SPL |
|---|---|
| Whisper | 20-30 dB |
| Normal conversation | 60-70 dB |
| City traffic | 80-85 dB |
| Rock concert | 110-120 dB |
| Jet engine at takeoff | 140 dB |
Calculation Tips:
- To add decibels, use: 10 * log10(10^(dB1/10) + 10^(dB2/10))
- Two equal sound sources increase the level by 3 dB.
- Ten equal sound sources increase the level by 10 dB.
Safety Considerations:
| Exposure Time | Maximum Safe Level |
|---|---|
| 8 hours | 85 dB |
| 4 hours | 88 dB |
| 2 hours | 91 dB |
| 1 hour | 94 dB |
| 15 minutes | 100 dB |
Additional Information:
- A-weighting (dBA) is often used to approximate human hearing sensitivity.
- C-weighting (dBC) is used for peak measurements and low-frequency noise.
- The sound intensity is proportional to the square of the sound pressure.
- Sound pressure decreases with distance from the source (inverse square law).
This table provides a comprehensive overview of converting sound pressure to decibels, including key conversion points, common sound levels, safety considerations, and additional relevant information. This knowledge is crucial for acousticians, audio engineers, and anyone working with sound measurements and noise control.