A speakerless acoustic thermometer

Abstract

Existing acoustic thermometers are often implemented using speaker-microphone systems, which are power-consuming and inconvenient to operate. Here we demonstrate a simple speakerless acoustic thermometer, which is an acoustic Fabry–Perot resonator (AFPR) consisting of a tubular acoustic waveguide and a microphone whose diaphragm acts as a reflective surface of the AFPR. Theoretical analysis shows that the resonant frequency (RF) ( fm ) at a given mode order (m) for the AFPR is a linear function of m with the slope (Δf/Δm) depending on the ambient temperature. Therefore, when the linear relationship between fm and m for the AFPR is measured, the ambient temperature can be determined from its slope. The values of fm at different m can be easily obtained by using the AFPR to detect ambient white noise rather than the sound signal from a loudspeaker. The thermometric performance of the prepared AFPR was investigated in a range of temperatures from −17 °C to 60 °C. The measured temperatures show the mean absolute error below 0.9 °C relative to those simultaneously obtained with a commercial electronic thermometer. As experimentally demonstrated in this work, the AFPR can detect extremely weak white noise in the anechoic room and thus enables to accurate measure the ambient temperature there, attributable to its ultrahigh pressure sensitivity at each RF. The advantages of simple structure, low power consumption, convenient operation, and high detection accuracy offer the AFPR outstanding applicability for on-site temperature measurements in various environments.