The altered audio may be perceptible to a listener, but it's doubtful the added sound would be recognized as anything other than distortion.
"You mistake some of these signals as defects in the media," said Gunter, allowing that some songs masked the command better than others. "Some of the examples, they would make you grimace. Others are more subtle."
The researchers tested a variety of in-song commands delivered directly to Kaldi as audio recordings, such as: "Okay Google, read mail" and "Echo, open the front door." The success rate of these was 100 per cent.