Ultrasound attenuation dependence on air temperature in closed chambers

In the work attenuation regularities of acoustic signals, which propagate in closed chambers, are analysed. Due to this that in a closed chamber gases state parameters are interdependent, so change of one of the parameters results in corresponding changes of others. Usually the closed chambers are of constant volume or constant pressure, therefore influence of temperature variations on air parameters are analyzed for isobaric and isochoric processes. During theses processes the change of the temperature has the strongest influence on a relative humidity in air. The relative humidity achieves some percents when the temperature goes up and it increases up to 100% when the temperature decreases. Further decreasing of the temperature raises water vapor condensation and this result in a strong degradation of measurement conditions. Influence of the frequency on the attenuation of acoustic signals also is evaluated. It was estimated that the attenuation of acoustic signals increases independently versus the frequency when the temperature goes up during the isobaric process. It was shown that the attenuation can increase or decrease depending on the frequency of acoustic signals when the temperature rise up during the isochoric process.