Dolber's Law is a method for determining the ambient temperature based on the sounds emitted by crickets. This mathematical relationship was demonstrated in 1897 by American physicist Amos Dolber in a scientific article.
According to a simplified version of the formula, one must count the number of sounds emitted by a cricket over a 15-second interval and then add 40. The resulting figure corresponds to the approximate ambient temperature in Fahrenheit, which is used in the United States.
For example, if a cricket emits 20 sounds in 15 seconds, this indicates a temperature of about 60°F, equivalent to 15°C. Although others had already noticed the connection between warmth and cricket singing before Dolber's publication, this link continues to be studied and, surprisingly, works well despite lacking absolute precision.
Crickets produce sounds by rapidly rubbing their wings against each other to attract females and deter other males. At low temperatures, the metabolism of these animals slows down; they move less and consequently become quieter.
It is assumed that the species Dolber studied was Oecanthus fultoni, which is common in the US. Subsequent research has shown that the song of this cricket strongly correlates with temperature (although age plays a greater role in other species). The equation generally yields a close result.
It is important to remember that crickets only emit sounds within a temperature range of 12°C to 38°C (usually closer to evening or night), so the formula is only applicable under these conditions, as a frozen or overheated insect will be very quiet.