Congress has passed a bill which will standardize the siren tones used by emergency services across the county for the first time. Rather than use the common Whoop and Wail style siren, a two-tone siren similar to the old sirens used in the UK and parts of Europe is to be adopted.
Extensive testing by independent laboratories has shown that the simple two-tone siren is more effective than whoop & wail. It is far easier to hear and identify the two-tone siren when there is a lot of ambient noise, and it is also easier to recognize the direction the sound is coming from. This contradicts information from previous studies, although it seems that this was not new information to the emergency services themselves. Their adoption of the whoop and wail sirens has often been put down to machismo rather than practicality.
In the UK, the two-tone siren was standard for many years after it was used in place of bells on vehicles. It has only been replaced with whoop and wail over the last twenty years following a massive exposure to our cop shows on UK TV. In fact the UK's recent siren, known as a Wail, Yelp and Piercer, has three modes, including a 'chattery' Piercer tone which is designed to be the most assertive.
The latest research indicated that the two-tone is still more effective than Wail Yelp & Piercer in real emergency situations.
It will be interesting to see what happens in the UK once the US sirens are consolidated on the new two-tone style and this is reflected in our TV shows.