Acoustic probe for temperature measurement suitable for operation with audio interfaces having random input/output delays

Abstract

Measuring temperature distribution is an important technique in the fields of meteorology, agriculture, and architecture. The acoustic probe emits sound waves from a speaker and measures the time it takes for the waves to reach a microphone, enabling the measurement of the average temperature between the speaker and the microphone. Additionally, by placing multiple acoustic probes around the measurement area, it becomes possible to measure the temperature distribution using fewer sensors compared to point-type sensors. However, acoustic probes can have higher costs due to the requirement for externally controllable setups or interfaces with minimal audio input/output (I/O) delays. To address this issue, we propose an acoustic probe that achieves accurate measurements even with a low-cost audio interface featuring random I/O delays. The proposed acoustic probe measures the delay time from the recording start to the playback start. This design cancels the error of sound wave propagation time caused by random delays in the audio interface. Through temperature measurement experiments using the proposed acoustic probe, it was revealed that precise measurements (the error of the proposed probe was 0.34°C, while the error of the existing probe was 4.88°C) could be achieved by canceling the random delays in the audio interface.