If you have the Schlage BE469 lock installed, it has a special Alert mode with an adjustable sensitivity. With the highest level of sensitivity it can detect a knock on the door and chimes the lock (it’s got a loud chime / 85db siren built into it). The neat thing is that it only chimes when the locked is locked, so when you unlock the door to open it, it wont’ chime (which is what you had wanted).
The lock reports triggers over Z-Wave which can be captured by a DTH so it can be used to trigger other alarms, chimes etc, however if I remember correctly it only reports Tamper and Forced entry triggers and not the Alert triggers, so if you’re okay with the build in Chime it’ll meet your needs.