School Lockdown Alerts: Why Audio Alone Is Not Enough

An audio lockdown alarm tells staff that something is wrong. A visual alert tells them what is wrong and what to do. As schools, colleges and MATs prepare for Martyn’s Law, the most effective school lockdown alerts use both sound and visuals.

What Martyn’s Law means for school lockdown procedures

The Terrorism (Protection of Premises) Act 2025, known as Martyn’s Law, received Royal Assent in April 2025. It has an implementation period of at least 24 months, so duties are expected to take effect from spring 2027. Schools and colleges sit in the standard tier, even if they expect 800 or more people on site. That tier requires procedures for evacuation, invacuation, lockdown, and communicating with people on site during an incident.

A lockdown procedure only works if everyone on site knows it has started, and knows which procedure applies. For a full overview, see our Martyn’s Law page.

Where an audio lockdown alarm falls short

Audio alarms are fast at getting attention. In a school, they also have clear limits:

• One tone, several meanings. British Standard BS 5839-1 states that fire alarm evacuation tones should not be used for anything other than fire. The Fire Industry Association guidance confirms that a lockdown alarm must use a distinct tone. But even with distinct tones, staff still need to recognise each one and remember what action to take, often under pressure.
• Spoken announcements are slow and easy to miss. Speech arrives one word at a time. Miss the first few words, or stand in a room with poor acoustics, and the message is lost.
• Not everyone on site hears the alarm. There are more than 53,000 deaf children and young people in the UK, and 78% of school-aged deaf children attend mainstream schools. Sports halls, music rooms, workshops and dining halls are loud. Some students and staff are deaf or hard of hearing. Some students with SEND, including many autistic pupils, find sudden loud sounds distressing.
• A tone carries no detail. A lockdown alarm cannot tell a supply teacher what to do or confirm if an alert is a drill.

How visual alerts speed up staff response

People take in visual information very quickly. Researchers at MIT found that people could identify the content of an image seen for as little as 13 milliseconds. A colour-coded screen with a clear instruction, such as “Lockdown: close doors, stay out of sight”, gets its meaning across in a single glance.

That is the difference between being alerted and being informed. Visual alerts on classroom displays and staff devices deliver both at once, in every room:

• Staff respond with confidence, including cover and supply staff who don’t know the site’s alarm tones.
• Each procedure looks distinct, so lockdown is not mistaken for evacuation or invacuation.
• The alert reaches people who can’t hear it, including anyone in a noisy space.
• An all-clear or updated instruction reaches every room at the same time.

Why audio and visual lockdown alerts work best together

Research on the redundant signals effect shows that people respond faster when the same signal arrives through sight and sound together. In one 2019 study, average reaction times were 321 milliseconds for combined audio and visual signals, compared with 371 milliseconds for audio alone and 382 milliseconds for visual alone. The sound gets attention. The visual confirms the message and adds the detail.

For Martyn’s Law readiness, this layered approach makes sure every person on site receives the alert and knows how to act on it.

Four questions to test your school lockdown alerts

1. Can every space on site receive a lockdown alert, including halls, fields and workshops?
2. Can staff tell lockdown, invacuation and evacuation apart straight away?
3. Does the alert reach people who can’t hear it?
4. Can you send an all-clear or updated instruction to every room at once?

How Vivi supports active crisis resilience

Vivi is the campus operating system for schools, bringing crisis response, communications and instruction together on the screens already up in your school. For crisis response, Vivi provides three layers:

1. Visual alerts on every display, triggered in seconds.
2. Vivi Device Alerts, which take over the full screen of every staff laptop and require staff to acknowledge the alert, so you know who has seen it.
3. An auditable record of every incident, for post-incident review and for showing how your lockdown procedures work in practice.
4. Audio alerts (coming soon!) designed to bring sight and sound together on one platform, without a separate PA system

Reviewing how your school alerts people on site is one of the simplest places to start preparing for Martyn’s Law, and one of the most important. Combining audio with visual alerts on the screens already up in your school means every member of staff gets the alert and knows exactly what to do.

See how Vivi can help you support Martyn’s Law readiness.