An alternative to audioBoom, SoundCloud allows private storage. Publish up to 3 hours of recordings for free.

SoundCloud works in a similar way to one of our long term favourite apps - AudioBoom - there is an app or you can record / upload audio from your PC.  The difference is that you can opt for your audio to be public or private and with the private setting - you can still share with specific people, it just won't be visible / searchable generally. You can even try transcribing your audio with SpeakerText