Decibel Distance Calculator

Example: A 91 dB gas mower drops to about 67 dB at 50 ft

How loud is a lawnmower from the porch, a concert from the back of the field or a shout from across the street? Pick a sound and a distance to see its level, how long your ears can take it, and how far it carries before the background drowns it out.

Last reviewed by SparkCalc editorial team · October 2026

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Units

Sound source

Your distance from the source

Target level

Background noise

Source shape

Include air absorption

Sound level as you move away

Every sound at your distance

Sound Level at Your Distance

Safe Listening Time

Sounds Like

Distance to Your Target Level

Hearing-Safe Distance

How Far It Carries

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How to use this calculator

Choose feet and miles or metres and kilometres.
Pick a sound, or choose "Enter my own level" and type a reading from a sound meter with the distance it was taken at.
Enter how far you are from the source.
Set a target level (85 dB is the 8-hour hearing limit) and the background noise where you are.
Read the level at your distance, the safe listening time, and how far away the sound fades into the background.

How We Calculate This

Point source: L₂ = L₁ − 20 × log₁₀(d₂ / d₁), the inverse square law, which removes about 6 dB per doubling of distance. Line source (a road or a train): L₂ = L₁ − 10 × log₁₀(d₂ / d₁), about 3 dB per doubling. With air absorption on, the calculator also subtracts 5.0 dB per kilometre, the ISO 9613-2 attenuation at 1 kHz, 20 °C and 70% relative humidity; higher pitches are absorbed faster and low rumbles much slower. Safe listening time follows the NIOSH recommended exposure limit: 8 hours at 85 dBA, halved for every 3 dB above it, with 140 dB as the ceiling. Firework and gunshot presets are peak levels, so they are compared with the 140 dB peak limit rather than given a time. Source levels: speech from ANSI S3.5 at 1 m; whisper, mower, leaf blower and concert from the ASHA noise chart; motorcycle at 25 ft and jet takeoff at 200 ft from the Purdue noise comparison chart; firework from ASHA at 3 ft; gunshot from NIOSH firearm measurements (most recreational guns peak at 150 to 165 dB). Where a chart gives no distance, the listening position is taken as 1 m from the operator, and 10 m from the speakers in a concert crowd. "How far it carries" is the distance where the sound falls to the background level; a sharp or tonal sound can still be noticed a little below a steady background. Real outdoor sound also depends on wind, temperature layers, the ground and obstacles, which this model leaves out.

Methodology last reviewed: October 2026. How SparkCalc works

Sources: NIOSH: Understand Noise Exposure (85 dBA REL and 3 dB exchange rate) · NIOSH: About Noise (hazardous noise and the recommended exposure limit) · NIOSH (1998). Criteria for a Recommended Standard: Occupational Noise Exposure, Publication 98-126 · American Speech-Language-Hearing Association: Loud Noise Dangers (noise chart) · NIDCD (NIH): Noise-Induced Hearing Loss · Purdue University Chemistry: Noise Sources and Their Effects (noise comparison chart) · CDC Stacks: Prevention of Noise-Induced Hearing Loss from Recreational Firearms · ANSI S3.5-1997 (R2020). Methods for Calculation of the Speech Intelligibility Index (standard speech spectrum levels at 1 m) · ISO 9613-2: Acoustics, Attenuation of sound during propagation outdoors, Part 2 (atmospheric absorption coefficients)

Why doubling the distance only takes off 6 dB

Sound from a mower or a speaker spreads out like the surface of a growing balloon. Double your distance and the same energy covers four times the area, so each square inch gets a quarter of it. A quarter of the energy is 6 dB less. That is why stepping back from 1 metre to 2 metres helps much more than stepping back from 50 to 51 metres.

Distance is the cheapest hearing protection

At 112 dBA, a typical concert crowd level, the NIOSH limit is about one minute a day. Each 3 dB lower doubles that time, and each doubling of your distance from the speakers takes off about 6 dB, or four times the safe time. Moving from 10 to 40 metres away buys roughly sixteen times more safe listening, before you add earplugs.

Why sound carries farther on some nights

This calculator assumes still, even air. On calm, clear nights the ground cools and a warm layer forms above it, bending sound back down so distant traffic, trains and voices carry much farther than usual. Wind does the same downwind and the opposite upwind. Background noise matters too: a voice that is lost against daytime traffic can stand out clearly on a quiet rural night.

Key terms

Decibel (dB): A logarithmic unit of sound level. Every 10 dB is ten times the sound energy and sounds about twice as loud.
dBA: A decibel reading weighted to match how human ears hear different pitches. Hearing limits are set in dBA.
Inverse square law: Sound from a single source spreads over a growing sphere, so its intensity falls with the square of distance: about 6 dB per doubling.
Peak level (dBP): The highest instantaneous pressure of a short bang such as a gunshot. It is judged against a 140 dB limit, not a daily time.
Exchange rate: How many decibels halve the safe listening time. NIOSH uses 3 dB, so 88 dBA is safe for 4 hours instead of 8.

Frequently Asked Questions

How much does sound drop with distance?

From a single source in open air, the level falls by about 6 dB every time you double your distance, because the same energy spreads over four times the area. A mower at 91 dB from 1 metre is about 85 dB at 2 metres and 79 dB at 4 metres. A long source such as a busy road or a train drops only about 3 dB per doubling. Air also absorbs sound, which matters over hundreds of metres.

How far does a 120 decibel sound travel?

A 120 dB sound measured 1 metre away falls to 85 dB about 55 metres (180 ft) away, and in this model stays louder than a 40 dB quiet room for roughly 2.5 km (1.5 miles), allowing for air absorption at 1 kHz. Wind, temperature layers, buildings and the ground can shorten or stretch that a lot outdoors.

How long can I safely listen to a loud sound?

NIOSH recommends no more than 85 dBA averaged over an 8-hour day, and halves the allowed time for every 3 dB above that: 4 hours at 88 dBA, 1 hour at 94 dBA and 15 minutes at 100 dBA. Impulse sounds such as gunshots and firecrackers are judged by their peak, and NIOSH sets 140 dB peak as the level no one should be exposed to without protection.

How far can a human voice be heard?

ANSI speech data put a normal voice at about 62 dB and a shout at about 82 dB, measured 1 metre from the speaker. On a quiet rural night (30 dB) a normal voice stays above the background for about 40 metres and a shout for roughly 300 to 400 metres in still air. Any wind, traffic or rain cuts that sharply.

Is 10 dB quieter really half as loud?

Roughly, yes. A 10 dB drop cuts the sound energy to a tenth, but people hear it as about half as loud. That is why moving four times farther away (about 12 dB quieter) makes a sound seem a bit less than half as loud, not a sixteenth.

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This calculator provides estimates for educational purposes only. Real sound levels vary with the source, the weather and the surroundings, and a calculation is no substitute for a sound level meter. If you are regularly around loud noise, wear hearing protection and consult an audiologist or healthcare professional about your hearing.

References