Cirrus Research on a rescue mission. When paramedics race through the streets on a call-out, the siren is a very familiar and omnipresent sound. The acoustic warning signal is indispensable for rescue teams, police and the like to get to the scene of the emergency as quickly as possible. But just how loud is the siren? In collaboration with Thorsten Staarmann, Operations Manager of the Frankfurt and Main-Taunus district ambulance service of the Malteser Hilfsdienst, and using our Optimus sound level meter, we took a closer look.
What you should know about the use of the siren:
- Das Martinshorn darf nur in Verbindung mit dem Blaulicht genutzt werden.
- In diesem Fall darf der Fahrer des RTW nach §38 StVO das sogenannte „Wegerecht“ in Anspruch nehmen. Das heißt, dass Verkehrsteilnehmer dem Rettungswagen Platz machen müssen.
- Das Wegerecht ist aber nicht mit dem Sonderrecht gleichzusetzen, das die Abweichung von der Straßenverkehrsordnung erlaubt (wie beispielsweise eine rote Ampel überqueren). Fahrzeugführer des Rettungsdienstes dürfen sich nur über die Regeln der StVO hinwegsetzen, wenn höchste Eile geboten ist, um Menschenleben zu retten oder schwere gesundheitliche Schäden abzuwenden. Selbiges gilt beispielsweise auch für Privat-PKWs, sollten diese einen bedrohlich Verletzten oder eine Gebärende ins Krankenhaus befördern.
- Trotzdem müssen sich Fahrer eines RTW weitestgehend an die Straßenverkehrsordnung halten. Polizei und Feuerwehr dürfen beispielsweise in bestimmten Situationen zusätzlich zum Wegerecht das sogenannte „Sonderrecht“ in Anspruch nehmen. In diesem Fall sind die Fahrzeuge nach §35 StVO von den Vorschriften der Straßenverkehrsordnung befreit.
- Auf dem RTW des Malteser Hilfsdiensts steht das Wort „Rettungsdienst“ spiegelverkehrt auf der Motorhaube, damit vorausfahrende Fahrzeuge im Rückspiegel lesen können, welches Fahrzeug angefahren kommt.
An ambulance siren – two sounds
What many people don’t know is that the siren produces two different sounds: every Malteser Hilfsdienst ambulance has an electric horn and a compressed air horn (the Martin horn), each of which plays signals of a specific fundamental frequency (standardised according to DIN 14610).
The sound of an electric horn
When paramedics race to an emergency, the electric horn is a very present noise and warning for the rest of the traffic. The acoustic warning signal is indispensable for rescue teams, police and the like to get to the scene as quickly as possible.
The air horn
The siren is not always used: the Malteser Hilfsdienst uses the siren on the way to the scene depending on the situation and on the instructions of the control centre or the medical officer.
Measuring noise levels in ambulances – the peak values of the measurements
Sound pressure level of electric siren and siren from a distance of 1.5 metres
First, the electric siren of the Malteser ambulance was measured from a distance of 1.5 metres. This resulted in an average noise level of 109.45 decibels (dB), which is roughly equivalent to the noise of a chainsaw. The maximum value measured was 120.73 dB. This is the noise level at a rock concert, for example. In combination with the siren, the average noise level was slightly quieter at just 107.65 dB. This is because a compressed air horn diffuses the sound differently and is therefore more effective at a greater distance. Nevertheless, the noisy combination still reached a peak value of 126.91 dB.
Maximum values of the measurement
- Electric horn – 120.73 dB
- Electric horn and siren – 126.91 dB
Siren volume from a distance of 20 metres
From a distance of 20 metres, it was a few shades quieter: the electric horn reached 97.55 dB – the noise level in a sawmill, for example. Together with the air horn, the hundred-decibel mark was exceeded again, and at 103.54 dB, the noise level was roughly comparable to a disco. The peak values here were 109.39 dB and 119.53 dB.
Maximum values of the 20-metre measurement
- Electric horn – 109.39 dB
- Electric horn and siren – 119.53 dB
Sound level measurement in the driver's cab
Last but not least, the noise level in the driver’s cab of the ambulance was measured. The well-insulated interior reduced the noise level to an average of 83.33 dB (E-Horn only) and 85.73 dB (E-Horn and siren).
Maximum values of the measurement in the driver's cab
- Electric horn – 99.92 dB
- Electric horn and siren – 104.85 dB
Conclusion: noise level measurement in ambulances
The measured values all lie between 85 and 127 decibels, which can be compared to a heavily travelled road versus a jet aircraft. A siren in operation poses no risk to pedestrians or road users. Although the warning signal reaches an immense noise level, it would only be harmful to health if it were to be exposed to over a long period of time. Furthermore, paramedics, police and fire brigade only use the siren in emergencies or on the instructions of the emergency doctor.
