Sound spreading with distance calculator

Free-field point-source spreading; no ground or atmospheric effects.

acoustics-distance-loss.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	levelDb
	67.9588
	51.9588

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

level budget in dB67.96 ✓ passes

BASELINE INPUTS

referenceLevel80 referenceDistance1 mdistance4 m

CALCULATED

levelDb67.959

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Sound spreading with distance
# Scope: Free-field point-source spreading; no ground or atmospheric effects.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

referenceLevel = 80
referenceDistance = 1 m
distance = 4 m

levelDb := referenceLevel-20*log10(distance/referenceDistance)

check level budget in dB: levelDb <= 70

scenario alternative: referenceLevel = 64

Calculated from your source · not saved

Baseline · Baseline

level budget in dB67.96 ✓ passes

alternative · alternative

level budget in dB51.96 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

level db: levelDb = referenceLevel-20*log10(distance/referenceDistance)

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

reference level: 80
reference distance: 1 m
distance: 4 m

Calculated

level db: 67.9588

Assumptions and limits

Free-field point-source spreading; no ground or atmospheric effects.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Sound spreading with distance. Inputs: reference level; distances; propagation geometry. Outputs: idealized level change. Model scope: Small-signal vibration and declared sound-propagation conditions. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: reference level, distances, propagation geometry
Outputs: idealized level change
Modes: calculate, compare, sweep
Drawing: Spectrum and vibration animation

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS