Behind the result - No mystery in the method
Outdoor level at the wall = entered reference level − K × log10(wall distance ÷ reference distance), with K = 20 for an ideal free-field point source or 10 for an ideal continuous line source. Both distances must refer to the same source; the entered level must correspond to the reference distance, not a level already adjusted to the wall. Wall scenarios use illustrative allowances 15 / 25 / 35 dB and window scenarios 0 / 10 / 20 / 25 dB. These are deliberately simplified scenario knobs, not tested assembly data, STC/Rw ratings or claims about any real wall or window. With window fraction f, transmission proxy τ = (1 − f) × 10^(−wall allowance / 10) + f × 10^(−window allowance / 10). Combined allowance = −10 × log10(τ). Indoor proxy = wall level − combined allowance. Decibel allowances are combined through energy fractions, not averaged directly. The final proxy is rounded to one decimal place.
This is an educational scenario, not a calibrated room-level model. It omits frequency spectra, actual construction, gaps, vents, flanking paths, room absorption, reflections, ground, barriers, weather, source directivity and indoor sources. Using a phone guess as input does not turn the output into a measurement. Negative model values are not silence; the tool flags that the assumptions are outside a useful everyday interpretation.
This tool does not measure real decibels, fetch live prices or guarantee a specific noise reduction. Blank optional fields are omitted. Text is displayed literally, not interpreted as HTML.
Change inputs to explore another scenario. The old result is cleared when an input changes. Download text creates a local copy; Print / Save PDF uses your browser. Review notes before sharing and delete copies you no longer need.
Before you go
Is this a real noise measurement?
No. No microphone is used and no sensor or live source is consulted. The outdoor level is supplied by you, and the indoor number is an illustrative proxy calculated from simplified assumptions. Use an appropriate professional assessment for a real acoustic question.
Are the wall and window allowances verified performance figures?
No. They are transparent example values for comparing scenarios, not ratings of specific constructions. Real performance depends on the complete assembly, frequency, openings, installation and other paths. Do not use these values as product specifications or add them to an STC/Rw rating.
What if I already know the level outside my window?
Use that value as the reference level and enter equal reference and wall distances to make the distance adjustment zero. Do not attenuate a value twice. The wall/window model remains illustrative even with a measured outdoor input.
Does a low result mean the room will be silent or safe?
No. Indoor sources, low frequencies and unmodelled paths may dominate. The output is not a hearing-safety limit, compliance test or guarantee of comfort. Seek qualified advice for safety, disputes or building decisions.