The instrument function of a broadband (1.6–2.5 MHz) detector that is used in acoustic thermometry has been calculated. Experimental check shown that measured and computed results are in agreement. The effect of the pass band characteristics and the detector’s size on the instrument function has been studied as well as the effect that the instrument function has on an acoustic thermometric signal that is measured by the detector. The ratio of the wavelength (for the mean reception frequency) to the detector’s radius has been shown to be the main parameter that determines the acoustic thermometric signal at distances that are typical of acoustic thermometry. For problems of localizing a heated region, it is optimal to locate the receiver at a distance of 15–25 mm from the region. For example, for a detector 8 mm in diameter, the width of the instrument function at a level of 0.5 of the maximum is 1.2 ± 0.1 mm in this zone.
$^1$Kotel'nikov Institute of Radio-engineering and Electronics (IRE) of Russian Academy of Sciences\
$^2$Federal Research Center The Institute of Applied Physics of the Russian Academy of Sciences"