Ultrasonic - how loud is too loud?

[wwenze]

A project requires me to use an ultrasonic transmitter. The one I have on hand is capable of 115dB @ 30cm @ 32.8kHz.

How loud can I go? I'm the type that believes in what you cannot hear (or see) can still harm you.

Generally, for handheld measuring devices using sound, how loud do they go?

 

[wwenze]

Found this:

http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_24-securite/health-sante-eng.php

I intend to use 90-100dB if possible to keep on the safe side, don't mind using lower.

But since this is for distance measurement being too soft can hurt range, hence what's the usual SPL for portable/personal devices using sound?