Abstract: A gas concentration measurement device comprises: a transmission circuit and a transmission oscillator for transmitting first ultrasonic waves in a concentration measurement space and transmitting second ultrasonic waves, which continue temporally from the first ultrasonic waves in the concentration measurement space; a reception oscillator and a reception circuit for receiving the ultrasonic waves that have propagated through the concentration measurement space; and a propagation time measurement unit for determining, on the basis of the times at which the first ultrasonic waves and the second ultrasonic waves were transmitted and the times at which the first ultrasonic waves and the second ultrasonic waves were received, the time in which ultrasonic waves propagate through the concentration measurement space.

Abstract: A processor is configured to include a correlation object determination unit for establishing: a first to-be-correlated signal established on the basis of a first upper-limit rate of change, which is the rate of change of an upper-limit envelope of a direct wave signal, and a first lower-limit rate of change, which is the rate of change of a lower-limit envelope of the direct wave signal; and a second to-be-correlated signal established on the basis of a second upper-limit rate of change, which is the rate of change of an upper-limit envelope of a round-trip-delayed wave signal, and a second lower-limit rate of change, which is the rate of change of a lower-limit envelope of the round-trip-delayed wave signal. The processor is also configured to include a correlation processing unit for establishing a correlation value between the first to-be-correlated signal and a signal based on the second to-be-correlated signal.

Abstract: A gas concentration measurement device comprises: a transmission circuit and a transmission oscillator for transmitting first ultrasonic waves in a concentration measurement space and transmitting second ultrasonic waves, which continue temporally from the first ultrasonic waves in the concentration measurement space; a reception oscillator and a reception circuit for receiving the ultrasonic waves that have propagated through the concentration measurement space; and a propagation time measurement unit for determining, on the basis of the times at which the first ultrasonic waves and the second ultrasonic waves were transmitted and the times at which the first ultrasonic waves and the second ultrasonic waves were received, the time in which ultrasonic waves propagate through the concentration measurement space.

Abstract: A processor is configured to include a correlation object determination unit for establishing: a first to-be-correlated signal established on the basis of a first upper-limit rate of change, which is the rate of change of an upper-limit envelope of a direct wave signal, and a first lower-limit rate of change, which is the rate of change of a lower-limit envelope of the direct wave signal; and a second to-be-correlated signal established on the basis of a second upper-limit rate of change, which is the rate of change of an upper-limit envelope of a round-trip-delayed wave signal, and a second lower-limit rate of change, which is the rate of change of a lower-limit envelope of the round-trip-delayed wave signal. The processor is also configured to include a correlation processing unit for establishing a correlation value between the first to-be-correlated signal and a signal based on the second to-be-correlated signal.