Bell with Slash Emoji 🔕 is often to use warn that mobile or other devices must be put on silent or turned off before entering the quiet zone like a library, mosque, etc. This symbol emoji is used in Hospital 🏥 mostly.
NOTE: Bell with Slash was accepted in 2010 as part of Unicode 6.0 and in 2015 added to Emoji 1.0.
🔕 Muted Bell
🔕 Bell with Cancellation Stroke