Your dog will come running to you when you power up yor K-7!
All kidding aside, this is apparently normal. Pentax Europe GmbH addressed this concern in a FAQ media release:
http://media.pentax.de/downloads/photo/de/17531/Fragen%20und%20Antworten.pdf
Translation:
"When you turn the camera the camera makes a strange noise. A strange "noise and beep" is heard.
In the K-7, the aperture control is provided with a motor. Once powered up, it goes into the standby position. The difference between old/new and mechanically/electronically is especially audible using old K-lenses and the Low Beam key is engaged. Ultrasonic sensor cleaning in the K-7 is done on start-up. This process can be perceived as a high frequency sound."
I have no idea what the reference to a "Low Beam Key" means.