You're not able to alter the Subsound sensitivity on Cocoon simply because you don't need to!
Cocoon will learn what is normal in and around your home within the first few weeks of being installed but is always learning.
Cocoon listens and learns your home's Subsound generated when you are away (armed), and in the first 15 minutes after you return home (disarmed).
This way Cocoon understands what is normal for an empty home, and what Subsound is generated during entry, and by comparing the two can decide what to alert you about.
Cocoon ships with a blank brain with a default 'worry' level. For some homes, this could initially be a little too sensitive, and for others may be a little less sensitive, but this will adjust as Cocoon learns your Subsound.