Acknowledging an alarm in Notification Center means ‘I have seen the alarm and I’m working on it’ so that your colleagues know. It does not stop the alarm signal on site.
For the specific alarm that you acknowledge, you and your colleagues will stop receiving notifications. This does not mean that you will never receive notifications anymore for the selected alarm type: when the same alarm is activated again after more than 15 minutes of inactivity, this will appear as a new alarm in the overview and you will be notified again.