MatSnackBar and MatLiveAnnouncer: reducing notification noise in Angular Material alerts

Goal

Determine how to configure Angular Material’s MatSnackBar to deliver timely alerts that are audible‑free yet accessible, while avoiding persistent UI noise.

Constraints and Uncertainty

• Default duration is undefined, causing indefinite persistence.
• Providing an action string renders a dismiss button; omitting or setting config.actions: [] removes it.
• Rapid consecutive open() calls may stack, potentially causing flicker.
• Accessibility relies on MatLiveAnnouncer with polite or assertive modes, which do not trigger audible alerts.

Specific Questions

1. What duration value best balances visibility with noise reduction for brief informational messages?
2. How can we suppress the dismiss button while still ensuring screen‑reader announcements via MatLiveAnnouncer?
3. What is the observed behavior when queuing multiple MatSnackBar.open calls with short durations in rapid succession?