Symptoms: Fearful of the sound of a flushing toilet (especially in a public restroom), vacuum, hairdryer or dog barking. Excessively startled by loud or unexpected sounds.

All of the above!  For a long time Kate refused to flush the toilet when she went, and still skips it quite frequently.  But public restrooms are by far the worst.  The hollow sound in multi-stall restrooms seems to echo and amplify the sound, causing her to scream.   

These newer automatic flushing toilets add a whole new element of fear, as she's so small the sensor seems to lose her and they wind up flushing while she's still sitting!  Oh the horror!  The force with which they flush has her convinced she's about to be sucked right down. At the library one day she had to go, but it kept flushing prematurely, so she's hop off and claim to be done, but then still have to go about 5 minutes later, so we'd try again, but she'd get freaked before she was finished, again...after about 4-5 attempts we just had to go home so she could finish going in peace.

Hand dryers in restrooms are another source of panic, primarily because of the noise, but also because of the hot blast of air.  She also hides when I use my hairdryer and the vacuum.

We got a beagle a year ago, and thankfully she's not too much of a barker, because Katie screams and practically jumps out of her skin at every little yelp, and nearly hyperventilates if Tess actually barks.  This extreme reaction to loud sounds was one of the first things that got me thinking of SPD.  Sometimes it's not even that a sound is too loud as much as if it's unexpected.  Where another kids might jump, Katie's whole body convulses and she's in tears.