Does Siri listen in without ones knowledge or permission, like Amazon’s Alexa?

Hello,

No, Siri differs from Alexa with voice recognition. With Alexa the device is constantly recording you and sending the recording up to Amazon for analysis looking for the key word "Alexa". Then Alexa will "turn on" and accept commands. Siri will listen for "Hey Siri" and that processing is performed locally on device. It is not until you purposely summon Siri does she start sending the recording to Apple for analysis.