Lockdown Alarm Sounds: Listen to All 32 Sounder Tones

A fire alarm means leave the building. A lockdown alert means stay inside and secure the room. Those are opposite instructions, and the only thing separating them for most people is what the alert sounds like.

Under stress, people do not carefully evaluate which of two similar sounds they are hearing. They pattern-match to the most familiar one and act. In almost every British school and workplace, the most practised alarm by a wide margin is the fire alarm.

That is the whole reason this list matters. Selecting a lockdown tone is not an aesthetic decision, it is a safety decision, and the right answer is whichever tone is least likely to be mistaken for the one your site already uses.

The library below contains every tone the sounders can produce. Each entry gives the tone number, the manufacturer’s name for it, the frequency and pattern, and the DIP switch code used to select it on the device.

A practical way to work through it is to identify your existing fire alarm tone first, then play candidates and rule out anything that sits close to it in pitch or rhythm.

The tones split broadly into low frequency, around 800 to 950 Hz, and high frequency, around 2400 to 2900 Hz. The difference is not loudness but how the sound behaves as it travels.

Lower frequencies travel further and pass through structure more effectively, which makes them useful where sound has to reach through doors and around corners. Higher frequencies are more directional and cut through background noise well, but are absorbed more readily by soft furnishings and lose energy faster over distance.

In practice, most sites end up using low frequency for general coverage and high frequency where there is significant background noise to overcome. What matters most is that whatever you choose remains clearly distinct from the fire signal.

Each tone is selected on the device using a five-position DIP switch, and the code column gives the switch positions. D means the switch is down, U means it is up, read left to right across the five positions.

So tone 19, the Slow Whoop, is DUDDU: first switch down, second up, third down, fourth down, fifth up. The device produces that tone until the switches are changed.

Worth noting for anyone maintaining a system: because the tone lives in the switch positions rather than in software, a replacement device will produce whatever its switches are set to. Recording your chosen code somewhere durable saves a lot of confusion when a unit is swapped years later.

Several entries in the list are not arbitrary sounds but recognised national or standard signals, and it is worth knowing which ones carry existing meaning before selecting them.

The Slow Whoop is widely associated with evacuation in the UK. The ISO 8201 pattern, sometimes called the temporal three, is an internationally recognised fire evacuation signal. The Australian Alert and Evacuation signals are defined in Australian standards, and the Swedish, French and Danish tones are national fire signals.

Choosing one of these for a lockdown alert is usually a mistake, because anyone who recognises it will act on the meaning they already know, which in most cases is evacuate. If your site has international staff or visitors, that risk is higher rather than lower.

We do not publish a single recommended lockdown tone, because the right answer depends entirely on what your fire alarm already sounds like. A tone that is ideal on one site is a poor choice on another for that reason alone.

The pattern we see work well is a lockdown alert that differs from the fire signal in both pitch and rhythm, not just one of them. A continuous tone against an intermittent fire signal, or a sweeping tone against a steady one, gives people two distinguishing features rather than one.

It is also worth pairing the tone with a visual difference. Blue beacons where fire uses red gives a second channel that does not depend on hearing or on remembering which sound means what. Where clarity matters most, voice announcements remove the interpretation step entirely.

A tone that sounds obviously distinct through headphones in an office can be far less distinct through a sounder in a busy corridor. Listening conditions matter, and the decision deserves testing in the environment it will actually be used in.

If you are already having a system installed, ask for candidate tones to be demonstrated on site during commissioning. Hearing them through the actual devices, in the actual spaces, is the only reliable test.

Once chosen, tell staff what it sounds like and practise with it. A distinct tone that nobody has heard before the day it matters is only half a solution, and the training is what turns the signal into a response.