Ultrasonic speaker for Arduino Mega

I am curious if it is possible to generate ultrasonic sounds with the Arduino Mega. The standard piezo buzzer only reaches 10kHz and I need to hit the 50kHz range, and upwards if possible. I have been told that the clock speed is not fast enough to generate such sounds. If that is not true, is there a buzzer I can use to produce these sounds?

Standard 40kHz Murata ultrasonic transducer.

I have been told that the clock speed is not fast enough to generate such sounds.

Who told you that?

I do not see any such component provided by Murata. Can you post a link or maybe an alternative device?

Really?

There is the tone() library which could go in excess of 60kHz, and now there is the improved toneAC() library which is said to go even higher.

http://playground.arduino.cc/Code/ToneAC