Enter the sound levels in decibels (dB) and corresponding time intervals in seconds into the calculator to determine the equivalent continuous sound level, known as Leq. The Leq represents the steady sound level that, over the same period of time, conveys the same sound energy as the varying levels.
Leq Noise Formula
The equivalent continuous sound level, Leq, converts a changing noise pattern into one steady sound level that would contain the same total acoustic energy over the same measurement period. This matters because decibels are logarithmic, so a true noise average cannot be found by simply adding dB values and dividing by the count.
L_{eq} = 10 \log_{10}\left(\frac{\sum_{i=1}^{n} t_i \cdot 10^{L_i/10}}{T}\right)T = \sum_{i=1}^{n} t_iWhat Each Variable Means
- Leq: the equivalent continuous noise level, reported in decibels.
- Li: the sound level during interval i.
- ti: the duration associated with sound level Li.
- T: the total measurement time across all intervals.
- n: the number of sound-level intervals entered.
In practical terms, the calculator converts each decibel reading into linear sound energy, weights it by how long it lasts, averages that energy over the full time period, and then converts the result back to decibels.
How to Use the Leq Noise Calculator
- Enter each measured sound level in decibels.
- Enter the matching time interval for each sound level.
- Select the time unit being used: seconds, minutes, or hours.
- Make sure the number of sound levels matches the number of time intervals.
- Calculate the result to obtain the energy-equivalent continuous noise level.
The loudest periods usually influence the result the most, especially when they last for a meaningful portion of the total time.
Why You Should Not Average dB Values Directly
Decibels are logarithmic. A higher reading represents disproportionately more sound energy, so a simple arithmetic mean understates the influence of loud intervals. Even when two time periods are equal, the correct Leq is found only after converting from dB to linear scale.
L_{eq} = 10 \log_{10}\left(\frac{10^{60/10} + 10^{70/10}}{2}\right) \approx 67.4\ \text{dB}In that case, the correct energy-based result is about 67.4 dB, not 65 dB. This is why short loud events can noticeably raise Leq.
Example Calculation
Suppose the measured noise history is:
- 85 dB for 120 seconds
- 90 dB for 150 seconds
- 95 dB for 180 seconds
First find the total duration:
T = 120 + 150 + 180 = 450
Then apply the Leq equation:
L_{eq} = 10 \log_{10}\left(\frac{120\cdot10^{8.5} + 150\cdot10^{9} + 180\cdot10^{9.5}}{450}\right)L_{eq} \approx 92.26\ \text{dB}This result is higher than a simple average of the listed dB values because the 95 dB segment contributes much more acoustic energy than the quieter segments.
Simplified Formula for Equal Time Intervals
If every sound level is measured over the same duration, the time terms cancel and the calculation becomes simpler:
L_{eq} = 10 \log_{10}\left(\frac{1}{n}\sum_{i=1}^{n} 10^{L_i/10}\right)This shortcut is useful when measurements are taken at evenly spaced intervals, such as one reading every second or every minute.
Important Input Tips
- Use matching lists: every sound level must have a corresponding time interval.
- Keep time units consistent: seconds, minutes, or hours are all valid as long as all intervals use the same basis.
- Do not mix weighting systems: if your readings are A-weighted, keep all inputs A-weighted.
- Longer intervals matter more: a level that lasts twice as long contributes twice as much time-weighted energy.
- Short loud bursts still matter: because of the logarithmic scale, brief high-level noise can noticeably increase Leq.
When Leq Equals the Measured Level
If the sound level stays constant for the entire period, Leq is the same as that constant sound level.
\text{If } L_1 = L_2 = \cdots = L_n,\ \text{then } L_{eq} = L_1This makes Leq especially useful because it behaves exactly like an ordinary sound-level reading in steady conditions, while still handling fluctuating conditions correctly.
Where Leq Is Commonly Used
- Environmental noise studies near roads, rail lines, airports, and industrial sites
- Workplace exposure tracking for changing machine or process noise
- Construction and demolition noise assessment
- HVAC, equipment, and building acoustics comparisons
- Community noise monitoring and general compliance screening
Leq Compared With Other Noise Metrics
| Metric | What It Represents | Best Use |
|---|---|---|
| Leq | Single energy-equivalent level over a time period | Overall exposure and fluctuating noise summaries |
| Lmax | Highest measured sound level | Peak event identification |
| Lmin | Lowest measured sound level | Background floor checks |
| L10 / L50 / L90 | Levels exceeded for a percentage of the time | Noise variability and background characterization |
Common Mistakes
- Averaging dB readings directly instead of using the Leq equation
- Entering time values in mixed units without converting them first
- Using unmatched counts of levels and intervals
- Including peak or impulse readings that were not measured over a defined interval
- Comparing Leq results from different measurement durations without noting the time basis
Frequently Asked Questions
Does a louder but shorter interval affect Leq a lot?
Yes. Because the decibel scale is logarithmic, a short high-level interval can add far more energy than a much longer quiet interval.
Can I use minutes or hours instead of seconds?
Yes. Any time unit works if every interval uses the same unit. The ratio inside the formula stays valid as long as the durations are consistent.
What does LAeq mean?
LAeq is the equivalent continuous sound level calculated from A-weighted measurements, which are adjusted to better reflect human hearing sensitivity.
Is Leq the same as the loudest sound recorded?
No. Leq is an energy-based average over time, while the loudest recorded sound is usually reported as Lmax or a peak level.
