I actually use two things. A sound machine to block out the little noises that will get the ones sleeping with me in bed going. It helps so they don't hear all the little noises that a normal house creates. Also, the Lentek Bark Free
Amazon.com: Lentek Bark Free: Kitchen & Dining
Used on the ultrasonic it's amazing. I have one girl who won't even come upstairs if it's on. I guess she has sensitive ears.

So I unplug it if I need her upstairs but most of the time I have it plugged in until my younger ones understand they don't need to bark their heads off.