Translator's note: a term used on this site
The Sensory Exchange Rate
Updated
The sensory exchange rate is this site's name for a fixed way of converting a measurement from another species, or from another sense, into a reference a person can picture. It is a metaphor, not a scientific term. Stated without the metaphor, it is a unit conversion in which both quantities, their units and their sources are written out.
The term is used only where a page converts one quantity into another.
Why both currencies matter
An exchange rate means nothing unless you know both currencies. A line such as "a dog's nose is 10,000 times better than yours" gives a rate with neither. Better at what: picking up a fainter trace of one odor, telling two odors apart, or something else? Measured how, in which dogs, and against which human measurement?
A ratio that hides the two quantities behind it cannot be checked, so it cannot be used.
What a conversion on this site states
The quantity and unit on the measured side, with the species, the study and the measurement conditions.
The quantity and unit on the human side, with its own source.
The same unit and the same reference level on both sides. Decibel values measured at different distances, or against different reference pressures, are not compared with each other.
The arithmetic, written out so you can redo it.
What it does not claim
A conversion turns a number into something you can picture. It does not show what another animal experiences. Receptor measurements and descriptions of experience stay in separate sentences, and an exchange rate only ever converts the measurements.
Where it appears
In the bat echolocation entry, the frequency with the most energy in one species' search calls is set beside the usual upper limit for pure tones in young, healthy people. Both numbers are in kilohertz, each with its own source.
The mantis shrimp entry sets the span of the animal's color receptors beside a standard human reference span for light. Both spans are in nanometers, each with its own source, and the reference span is not a list of human receptors.