Noise Level Calculator
Compare decibel levels, combine multiple sound sources, calculate how noise drops with distance, and check safe exposure times based on OSHA and NIOSH standards.
Add multiple sound sources to calculate the combined noise level. Sound adds logarithmically -- two 80 dB sources produce about 83 dB, not 160 dB.
Calculate how sound decreases with distance using the inverse square law. Every doubling of distance reduces the level by approximately 6 dB.
Enter a noise level to see the maximum safe exposure time per OSHA and NIOSH guidelines.
OSHA Permissible Exposure Limits
| Sound Level (dB) | Max Duration (OSHA) | Max Duration (NIOSH) |
|---|---|---|
| 85 | 16 hours | 8 hours |
| 88 | 10.6 hours | 4 hours |
| 90 | 8 hours | 2.5 hours |
| 92 | 6 hours | 1.6 hours |
| 95 | 4 hours | 47 min |
| 97 | 3 hours | 30 min |
| 100 | 2 hours | 15 min |
| 102 | 1.5 hours | 9 min |
| 105 | 1 hour | 4.7 min |
| 110 | 30 min | 1.5 min |
| 115 | 15 min | 28 sec |
| 120 | 0 (avoid) | 9 sec |
| 130 | 0 (avoid) | <1 sec |
| 140 | Instant damage | Instant damage |
Convert between decibels (dB SPL) and sound pressure in pascals. The reference pressure is 20 micropascals (threshold of hearing).
dB SPL Formula
Where Pref = 20 μPa (0.00002 Pa), the threshold of human hearing at 1 kHz.
To convert back: P = Pref × 10(dB/20)
Common Noise Levels Reference
Use this table to understand where everyday sounds fall on the decibel scale. Remember that every 10 dB increase sounds roughly twice as loud to human ears.
| Source | Level (dB) | Visual Scale | Safety |
|---|---|---|---|
| Threshold of hearing | 0 | Safe | |
| Rustling leaves | 10 | Safe | |
| Whisper | 30 | Safe | |
| Library | 40 | Safe | |
| Normal conversation | 60 | Safe | |
| Vacuum cleaner | 70 | Safe | |
| City traffic (inside car) | 80 | Caution | |
| Lawn mower | 90 | Danger | |
| Power tools / motorcycle | 100 | Danger | |
| Rock concert | 110 | Danger | |
| Jet engine (25m) | 120 | Pain | |
| Threshold of pain | 130 | Pain | |
| Gunshot / fireworks | 140 | Pain |
How Decibels Work
The decibel scale is logarithmic, not linear. This means small numerical changes represent large differences in actual sound energy.
Key Relationships
- +3 dB = double the sound intensity (energy)
- +6 dB = double the sound pressure
- +10 dB = sounds roughly twice as loud to human ears
- +20 dB = sounds four times as loud
Why Logarithmic?
Human hearing spans an enormous range -- from the faintest detectable sound (0 dB) to sounds that cause instant damage (140+ dB). The actual pressure ratio between these extremes is about 10,000,000 to 1. The logarithmic decibel scale compresses this range into manageable numbers.
Combining Sound Sources
Because decibels are logarithmic, you cannot simply add them. Two sources of 80 dB each do not produce 160 dB. Instead, the formula is:
Two identical sources add approximately 3 dB. So two 80 dB sources combine to about 83 dB.
Distance Attenuation (Inverse Square Law)
Sound spreads out as it travels from a source. In open air (no reflections), doubling the distance reduces the level by about 6 dB:
This assumes a point source in free field. Indoors, reflections from walls and ceilings reduce the effect of distance.
OSHA vs. NIOSH Noise Exposure Standards
Two major U.S. standards govern occupational noise exposure:
OSHA (Occupational Safety and Health Administration)
- Permissible Exposure Limit (PEL): 90 dB for 8 hours
- Exchange rate: 5 dB (every 5 dB increase halves allowed time)
- Maximum impact noise: 140 dB peak
- Formula: T = 8 / 2(dB - 90) / 5
NIOSH (National Institute for Occupational Safety and Health)
- Recommended Exposure Limit (REL): 85 dB for 8 hours
- Exchange rate: 3 dB (every 3 dB increase halves allowed time)
- Maximum exposure: 140 dB (impulse) or continuous noise limit
- Formula: T = 8 / 2(dB - 85) / 3
NIOSH is considered more protective of hearing. Many audiologists recommend following the NIOSH standard, especially for recreational noise exposure such as concerts, power tools, or headphone use.
Frequently Asked Questions
What is a decibel (dB)?
A decibel is a logarithmic unit used to measure sound intensity relative to a reference level. Because it is logarithmic, every 10 dB increase represents a tenfold increase in sound intensity. The reference level for sound pressure (dB SPL) is 20 micropascals, which is approximately the quietest sound a healthy human ear can detect.
How do you combine multiple sound sources in decibels?
You cannot simply add decibel values because the scale is logarithmic. Instead, convert each dB value to its linear intensity, sum those, and convert back: dB_total = 10 * log10(10^(dB1/10) + 10^(dB2/10) + ...). Two identical sources add about 3 dB. Ten identical sources add about 10 dB.
How does sound decrease with distance?
In an open environment, sound follows the inverse square law. Each doubling of distance from the source reduces the level by approximately 6 dB. At 10 times the distance, the level drops by 20 dB. This assumes a point source outdoors with no reflective surfaces nearby.
What are OSHA permissible noise exposure limits?
OSHA sets workplace noise limits starting at 90 dB for 8 hours. For every 5 dB increase, the allowed time is halved: 95 dB for 4 hours, 100 dB for 2 hours, 105 dB for 1 hour. Above 115 dB, no continuous exposure is permitted.
What is the difference between OSHA and NIOSH noise standards?
OSHA uses a 5 dB exchange rate with a 90 dB baseline for 8 hours. NIOSH uses a stricter 3 dB exchange rate with an 85 dB baseline for 8 hours. NIOSH guidelines are more conservative and are recommended by hearing health professionals.
At what decibel level does noise become dangerous?
Prolonged exposure above 85 dB can cause gradual hearing loss. At 120 dB, sound causes physical discomfort. At 140 dB and above, even brief exposure can cause immediate, permanent hearing damage. Always wear hearing protection when exposed to sounds above 85 dB for extended periods.
What is sound pressure level (SPL)?
Sound pressure level quantifies the pressure variation caused by a sound wave. It is measured in pascals (Pa) and converted to the dB SPL scale using the formula: dB SPL = 20 * log10(P / 0.00002), where 0.00002 Pa (20 micropascals) is the reference threshold of hearing.
Does this calculator store my data?
No. All calculations run entirely in your browser. No data is sent to any server, and nothing is stored.
Privacy & Limitations
Privacy: This calculator runs entirely in your browser. No data is transmitted or stored anywhere.
Limitations: These calculations assume ideal conditions (point source, free field, no reflections). Real-world noise levels depend on many factors including room acoustics, barriers, ground absorption, wind, and temperature. OSHA and NIOSH limits are occupational guidelines -- consult an audiologist for personal hearing health advice.
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Noise Level Comparison Calculator FAQ
What is a decibel (dB)?
A decibel (dB) is a logarithmic unit used to measure sound intensity. Because it is logarithmic, every 10 dB increase represents a tenfold increase in sound intensity. For example, 80 dB is 10 times more intense than 70 dB, and 90 dB is 100 times more intense than 70 dB.
How do you combine multiple sound sources in decibels?
To combine multiple sound sources, you cannot simply add decibel values. Instead, use the formula dB_total = 10 * log10(10^(dB1/10) + 10^(dB2/10) + ...). For example, two identical 80 dB sources combine to approximately 83 dB, not 160 dB.
How does sound decrease with distance?
Sound intensity decreases following the inverse square law. Every time you double the distance from a sound source, the level drops by approximately 6 dB. The formula is dB2 = dB1 - 20 * log10(d2/d1), where d1 is the reference distance and d2 is the new distance.
What are OSHA permissible noise exposure limits?
OSHA sets permissible exposure limits (PEL) for workplace noise. At 90 dB, the maximum exposure is 8 hours. For every 5 dB increase, the allowed time is halved: 95 dB for 4 hours, 100 dB for 2 hours, 105 dB for 1 hour, and 115 dB for 15 minutes or less.
What is the difference between OSHA and NIOSH noise standards?
OSHA uses a 5 dB exchange rate with a 90 dB threshold for 8 hours. NIOSH uses a more conservative 3 dB exchange rate with an 85 dB recommended exposure limit for 8 hours. NIOSH standards are considered more protective of hearing.
At what decibel level does noise become dangerous?
Prolonged exposure to noise above 85 dB can cause hearing damage. Sounds at 120 dB cause immediate discomfort, and exposure to 140 dB or above can cause instant permanent hearing damage. Even brief exposure to very loud sounds like firearms (140-165 dB) requires hearing protection.
What is sound pressure level (SPL)?
Sound pressure level (SPL) is the pressure variation caused by a sound wave, measured in pascals (Pa). The dB SPL scale uses 20 micropascals as the reference pressure (the threshold of human hearing). The formula is dB SPL = 20 * log10(pressure / 0.00002).
Does this calculator store my data?
No. All calculations run entirely in your browser. No data is sent to any server, and nothing is stored.