Sound reference
Technical unit workspace
- Quantities
- 3
- Systems
- SI / US
Common sound units:
- Decibel (dB SPL): logarithmic sound pressure level
- dBA: A-weighted decibels adjusted for human hearing
- Pascal (Pa): SI unit of sound pressure
- Phon: loudness level equal to dB SPL at 1kHz
- Sone: linear perceived loudness unit
- Watt/m²: sound intensity unit
Sound measurement has evolved significantly over time:
- Early 1900s: Introduction of the Bel unit by Bell Laboratories
- 1920s: Decibel (1/10 of a Bel) became standardized for telecommunications
- 1930s: Development of sound level meters and weighting curves
- 1940s: Introduction of phons for loudness levels
- 1950s: Standardization of sones for perceived loudness
- 1970s-present: Digital sound measurement technology and international standards
Sound units are used in various contexts:
- Audio Engineering: dB SPL, dBFS (Full Scale) for recording levels
- Environmental Monitoring: dBA for community noise assessment
- Medicine: dB HL (Hearing Level) for audiometry tests
- Physics: Pascals for absolute sound pressure measurements
- Acoustics: Phons and sones for subjective loudness studies
- Industrial: dBC for low-frequency noise monitoring
Sound Conversion Calculator
Quick answer
Formula: Np = B x 1.15128
Converting Bel to Neper with 6-place display precision.
Measurement type
Select a quantity to update available units
Quantity
Sound Level
Input unit
Bel (B)
Output unit
Neper (Np)
Understanding Sound Measurements
Decibel Scale and Sound Pressure
Sound is most commonly measured in decibels (dB), a logarithmic unit that expresses the ratio of a physical quantity relative to a reference level. The logarithmic scale is used because the human ear can detect an extremely wide range of sound pressures—from the threshold of hearing (20 μPa) to the threshold of pain (around 200 Pa).
The basic formula for sound pressure level in decibels is:
dB SPL = 20 × log₁₀(p/p₀)
where p is the measured sound pressure and p₀ is the reference pressure (20 μPa).
Sound Conversion Tables
Sound Pressure Level Units
| Unit | Symbol | Description | Reference |
|---|---|---|---|
| Decibel SPL | dB SPL | Sound pressure level | 20 μPa (hearing threshold) |
| Decibel A-weighted | dBA | Adjusted for human hearing | 20 μPa with A-curve |
| Phon | phon | Perceived loudness level | Equal to dB SPL at 1 kHz |
| Sone | sone | Linear perceived loudness | 1 sone = 40 phons |
Sound Pressure Units
| Unit | Symbol | Equivalent in Pascal |
|---|---|---|
| Pascal | Pa | 1 Pa |
| Micropascal | μPa | 10⁻⁶ Pa |
| Microbar | μbar | 0.1 Pa |
| Atmosphere | atm | 101,325 Pa |
Prefixed Units in Sound Measurements
| Prefix | Symbol | Factor | Example |
|---|---|---|---|
| micro | μ | 10⁻⁶ | μPa (micropascal) |
| milli | m | 10⁻³ | mPa (millipascal) |
| kilo | k | 10³ | kPa (kilopascal) |
| mega | M | 10⁶ | MW (megawatt) |
Practical Applications of Sound Measurements
Audio Engineering
- Using dB SPL and dBFS to calibrate recording levels
- Optimizing studio acoustics for high-quality sound reproduction
- Setting signal levels and gain structure in audio chains
Environmental Assessment
- Monitoring noise pollution in urban areas and industrial zones
- Assessing environmental impact of transportation and construction
- Measuring sound levels in natural habitats for ecological studies
Healthcare & Safety
- Conducting hearing tests with calibrated sound sources
- Measuring workplace noise exposure for occupational safety
- Designing hearing protection equipment
Architecture & Design
- Designing concert halls and recording studios with optimal acoustics
- Planning sound isolation in buildings and public spaces
- Measuring and managing reverberation times in rooms
Educational Resource
This educational video explains what decibels are and how they're used to measure sound levels. The video covers both theoretical concepts and practical applications of sound measurement, making it a valuable resource for understanding acoustic units.
Sound Conversion Resources
Get our comprehensive sound conversion chart showing decibels, phons, sones, and other sound units for quick reference when working with acoustic measurements.
Related Conversion Tools:
Sound Conversion FAQs
Find answers to common questions about sound measurements and conversions.
What are the main units used for measuring sound?
The main sound measurement units are: 1) Decibel (dB) - logarithmic sound pressure level, 2) dBA - A-weighted decibels for human hearing, 3) Pascal (Pa) - sound pressure, 4) Phon - loudness level relative to frequency, 5) Sone - linear perceived loudness, 6) Watt/m² - sound intensity.
How do you convert between different decibel scales?
Decibel conversions include: 1) dB SPL to dBA using frequency weighting curves, 2) dB = 20 × log₁₀(P/P₀) for pressure ratio, 3) dB = 10 × log₁₀(W/W₀) for power ratio, 4) Add 3 dB for doubling sound intensity, 5) Subtract 6 dB for doubling distance from source.
What are typical sound levels in decibels?
Common sound levels are: 1) Whisper: 30 dBA, 2) Normal conversation: 60 dBA, 3) City traffic: 80 dBA, 4) Power tools: 100 dBA, 5) Rock concert: 110 dBA, 6) Jet engine: 140 dBA, 7) Pain threshold: 120-130 dBA, 8) Workplace safety limit: 85 dBA for 8 hours.
How do you measure sound accurately?
Accurate sound measurement requires: 1) Calibrated sound level meter, 2) Proper microphone placement and orientation, 3) Consideration of background noise, 4) Appropriate frequency weighting (A, C, or Z), 5) Time weighting (Fast/Slow/Impulse), 6) Multiple measurement positions, 7) Environmental condition documentation.
What is the relationship between sound pressure and intensity?
Sound pressure and intensity relationships: 1) Intensity ∝ pressure², 2) Intensity decreases with square of distance, 3) 6 dB decrease per distance doubling for pressure, 4) 3 dB decrease per area doubling for intensity, 5) Power = intensity × area, 6) Reference pressure P₀ = 20 µPa.
How do frequency weightings affect decibel measurements?
Frequency weightings affect measurements by: 1) A-weighting (dBA) approximates human hearing, 2) C-weighting (dBC) for peak/impact noise, 3) Z-weighting (linear) for unweighted measurement, 4) B-weighting (obsolete) intermediate curve, 5) Different weightings can change readings by ±20 dB or more.
What factors affect sound measurement accuracy?
Sound measurement accuracy depends on: 1) Instrument calibration and quality, 2) Environmental conditions (temperature, humidity), 3) Background noise levels, 4) Reflective surfaces nearby, 5) Wind effects on microphone, 6) Measurement duration and averaging, 7) Distance and orientation to source.
How do you convert between loudness scales?
Loudness scale conversions: 1) 1 sone = loudness of 40 phons at 1 kHz, 2) Doubling sones = perceived twice as loud, 3) 10 dB increase ≈ perceived twice as loud, 4) Phons equal dB SPL at 1 kHz, 5) Stevens' power law relates physical intensity to perceived loudness.