Try recording your phrase holding the phone in slightly different positions. First, hold it like you were speaking to someone on the phone using the speakerphone. Then in the same position, but rotate the mic away from your mouth. Then, with the mic still away from your mouth, do it again at arm's length.
Obviously, a silent room is critical.
I've done that and had very good luck with it launching when I wanted it to. It has never once launched due to ambient noise. If that persists, take it back.
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