Medium conveyance apparatus with a plurality of sound wave sensors driven by single drive signal and outputting sound wave signals at different timings

A medium conveyance method comprising:

• determining a state of a medium based on a first sound wave signal outputted according to a received sound wave by a first sound wave receiver located to face a first sound wave emitter with a conveyance path in between, wherein the first sound wave emitter outputs a sound wave including an audible sound or ultrasonic wave, and a second sound wave signal outputted according to a received sound wave by a second sound wave receiver located to face a second sound wave emitter with the conveyance path in between, wherein the second sound wave emitter outputs a sound wave including an audible sound or ultrasonic wave, wherein
• a distance between the first sound wave emitter and the first sound wave receiver differs from a distance between the second sound wave emitter and the second sound wave receiver, and wherein
• the first sound wave emitter and the second sound wave emitter are located spaced apart in a direction intersecting with a medium conveyance direction, or the first sound wave receiver and the second sound wave receiver are located spaced apart in the direction intersecting with the medium conveyance direction.

A computer-readable, non-transitory medium storing executable instructions for conveying a medium, the executable instructions comprising:

• determining a state of a medium based on a first sound wave signal outputted according to a received sound wave by a first sound wave receiver located to face a first sound wave emitter with a conveyance path in between, wherein the first sound wave emitter outputs a sound wave including an audible sound or ultrasonic wave, and a second sound wave signal outputted according to a received sound wave by a second sound wave receiver located to face a second sound wave emitter with the conveyance path in between, wherein the second sound wave emitter outputs a sound wave including an audible sound or ultrasonic wave, wherein
• a distance between the first sound wave emitter and the first sound wave receiver differs from a distance between the second sound wave emitter and the second sound wave receiver, and wherein
• the first sound wave emitter and the second sound wave emitter are located spaced apart in a direction intersecting with a medium conveyance direction, or the first sound wave receiver and the second sound wave receiver are located spaced apart in the direction intersecting with the medium conveyance direction.