Noise Threshold Calculator
A published decibel figure on its own tells you almost nothing about whether a device is audible in the next room. What matters is the transmitted level at the listener's ear relative to the ambient noise floor already present in that room. This tool estimates that relationship.
Why the decibel figure alone is useless
Marketing pages quote a single number, usually the lowest setting, usually measured at an unspecified distance. Two problems follow. First, sound pressure falls with distance: in a free field it drops by about 6 dB every time you double the distance from the source, which means the figure changes substantially depending on where the microphone was. Second, the number describes the source, not the outcome. The outcome is a relationship between the transmitted level and whatever else is already making noise in the room next door.
The frequency effect most people miss
A partition does not attenuate all frequencies equally. Typical lightweight construction is comparatively effective against high frequencies and comparatively poor against low ones. That is why bass travels through a building while a television's dialogue does not. A device whose output is dominated by low-frequency vibration will transmit more energy through the same wall than a device that measures louder but produces mostly high-frequency content. This is the single most under-reported variable in consumer noise comparisons.
Cheaper interventions than changing the product
If the calculator puts you close to the threshold, the fastest fix is usually raising the ambient noise floor in the room someone else occupies. A fan or an air purifier moving the floor from 28 dB to 38 dB buys 10 dB of masking, which is frequently more than a product change would deliver. Physical options come second: a rug, a bookcase against the shared wall, a towel along the bottom of a door, and sealing obvious gaps all reduce transmitted and flanking sound at low cost.
Using this to compare two products
The most reliable way to use the tool is comparatively. Enter your actual room conditions once, note the margin, then change only the decibel figure and the motor character to represent a second device. The difference between the two margins is more trustworthy than either absolute number, because the model's assumptions cancel out when conditions are held constant.
Noise and privacy questions
How accurate is this calculator?
It is a first-order estimate, not a measurement. Real transmission depends on flanking paths (door gaps, outlets, shared ductwork, joist cavities) that a single wall number cannot capture. Treat the result as a way to compare two products or two rooms, not as a prediction of exactly what someone will hear.
Why does the calculator subtract 5 dB from the published wall rating?
Published Sound Transmission Class figures come from laboratory assemblies. Field performance across a real building is typically several points lower because of construction tolerances, penetrations and flanking transmission. A 5 dB field penalty is a conventional allowance.
Why does the motor character matter more than the decibel figure?
A wall attenuates high-frequency energy far more effectively than low-frequency energy. A device that produces low-frequency, rumbly output can be more audible through a wall than a louder but higher-pitched device, because the low-frequency content suffers less attenuation on the way through.
Can I make a room quieter without changing the product?
Raising the ambient noise floor in the listening room is usually the cheapest intervention. A fan, an air purifier or a white noise source at 35 to 40 dB masks a surprising amount of transmitted sound. Soft furnishings, a rug and a bookcase on a shared wall also help measurably.
What is the difference between dB and perceived loudness?
Decibels are a logarithmic ratio, so they behave unlike everyday numbers. A 10 dB increase is roughly a doubling of perceived loudness and about ten times the acoustic power. This is why a 6 dB difference between two devices is noticeable, while a 1 dB difference is not.