A 10MHz transducer will be resonant at 10MHz. If you drive it with a square wave at 10MHz, it will naturally respond best at frequencies that are 10MHz, and will very poorly respond to frequencies that are not 10MHz. Thus, a 10MHz square wave driving a 10MHz transducer will produce a pretty good 10MHz sine wave sound signal. This does depend on how sharp the resonance is of the transducer, but it shouldn't be that hard.
Ignoring that, creating a 10MHz RF sine wave isn't that hard using classical analog techniques: wifi chips in modern computers create a 5MHz carrier wave that can be amplified and doubled with some cheap off the shelf parts.
A 10MHz transducer will be resonant at 10MHz. If you drive it with a square wave at 10MHz, it will naturally respond best at frequencies that are 10MHz, and will very poorly respond to frequencies that are not 10MHz. Thus, a 10MHz square wave driving a 10MHz transducer will produce a pretty good 10MHz sine wave sound signal. This does depend on how sharp the resonance is of the transducer, but it shouldn't be that hard.
Ignoring that, creating a 10MHz RF sine wave isn't that hard using classical analog techniques: wifi chips in modern computers create a 5MHz carrier wave that can be amplified and doubled with some cheap off the shelf parts.