Measure Room Temperature Using Your iPhone

WHAT IS ONDO?

Ondo is an experimental acoustic thermometer implemented using an iPhone (or iPad) and headset. Acoustic thermometers utilise the principle that the speed of sound in air changes with temperature; by measuring the speed of sound it is possible to calculate air temperature.

HOW IT WORKS

Ondo transmits a high frequency sound from the earpiece. This sound is received by the microphone positioned at a fixed distance from the earpiece. The time taken for the sound to travel between the earpiece and the microphone is very accurately measured to less than a millionth of a second. The speed of the sound and hence the temperature of the air between the earpiece and the microphone can then be calculated (more details of this calculation can be found on our resources page).