“sorry, I didn't get that...” GVA announcement is triggered by external audio sources in Skype for Business Server 2015

When you have a Microsoft Skype for Business conference call ongoing in a Microsoft Skype for Business Server 2015 environment, participants in the conference call occasionally hear the following Group Virtual Assistant (GVA) announcement:

The GVA announcement is triggered by external audio sources that sound like a dual tone multi-frequency (DTMF) tone.

Note The external audio sources that are identified are as follows:

• A Windows notification sound that's confirmed to technically resemble the audio wave of the * DTMF tone.
• DTMF tones that are played by other phones in speaker mode nearby an audio device that's connected to a meeting.

To fix this issue, install the May 2017 cumulative update 6.0.9319.281 for Skype for Business Server 2015, Conferencing Announcement.