Answer:
negative informal sanction
Explanation:
An informal negative sanction describes informal sanctions or punishments that take any form and is exerted on an individual or group for going against certain social norms. These sanctions are "non-governmental" and "unofficial" and could take the form of: ridicule, embarrassments, gossip, insults, social ostracism etc. Like we observe in the above case, the lady is hushed(embarassed) for violating a social norm that requires people to be quiet during a classical music performance.
