That shouldn't happen. Would you be so kind as to tell me your OSX version and Mac/MacBook model? I probably won't be able to spot and fix the bug right away (it's new years tomorrow, after all) but on the long term I of course want to squash this kind of bug.
Ouch you're right. There's a case where I skip zero-ing out the history buffer. That means you hear the echo simulation for white noise... for a few ms. Sorry about that, will fix and report back.
OK I just replaced the installer on the website with a fixed version. When you re-install, please choose custom and deactivate installation of the kernel driver (otherwise you need to reboot afterwards, which can be avoided).
After the update, the app should be version 1.6.7 :)