Previously, whether your iPhone was muted or not, Siri's voice would loudly chime. With iOS 9, you can set Siri's voice to mute when your phone, too, is muted. This is easily changed in Settings and convenient when asking the new and improved Siri questions in quieter locations.
Open Settings and tap General.
Select Siri.
Scroll down to Voice Feedback and select Control with Ring Switch.
Now, when your ring switch is on mute, Siri will reply only in text.
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