Acoustic Hygrometer Based on Reverberation Time Measurement

In this paper, a hygrometer operated by acoustic means is proposed. It is important to measure spatial average humidity for environmental management in a room. In a large space, it is difficult to determine spatial average humidity because conventional sensors measure only local humidity at the measurement point. The proposed acoustic hygrometer utilizes the relationship between the sound attenuation coefficient and humidity. To measure the sound attenuation coefficient, reverberation time in a room is utilized. An acoustic hygrometer based on reverberation time achieves a noncontact measurement of spatial average humidity. As a practical examination, relative humidity ( RH) was measured on the basis of reverberation time in a chamber, and compared with reference values. The humidity measurement accuracy of the hygrometer was evaluated by statistical means because the measured reverberation time showed variability. From the results, the possibility of humidity measurement with an accuracy of about 5% RH at 50% RH or more using this hygrometer was verified. Here, the unit of RH is % RH. (C) 2012 The Japan Society of Applied Physics