What is the Siren actually listening to?

The microphone specifically listens for sound frequencies between 3000-4000 Hz which is what the majority of Smoke/CO alarms emit alarm sounds at according to UL 217 certification.  Any other sound that does not specifically fall under that range is filtered out. (human voice is between 60-300 Hz) Furthermore, all of the microphone data is processed locally on the device and is not stored or transmitted anywhere. 

No one, including Kangaroo, has access to any of the sound data.  Kangaroo takes its privacy extremely seriously and strives to build products that focus on their safety and security.