If you hear an intermittent hissing sound (like white noise) in your projects, this probably indicates you are using a plugin (VST) that is in 'trial' mode. The hissing sound is designed to allow the user to test a trial plugin while still protecting the product with an incentive to purchase the full version.
To disable the hissing sound you will need to either mute or delete the trial plugin or purchase it.
Image-Line plugins do not use intermittent white noise as a trial limitation. Image-Line trial plugins will either not save your plugin settings, or will have intermittent audio dropouts. So, it you hear periodic hissing this will likely be third-party plugin related.
Please note that this hissing has nothing to do with the 'Gibbs phenomenon' as some seem to think.
Image-Line Support Team