Sebastian-Terfloth-2280.jpg/jcr:content.jpg?t=1725364674659&height=99999&width=1140 "© Sebastian Terfloth")
Railways simply explained
04. 09. 2024
Everyone is familiar with microphones – on concert stages, on TV or in their own smartphones. A macrophone, on the other hand, is something very few people have at home. But they play a very important role in rail transport. Here's why.
The word 'macro' comes from the Greek 'makros', meaning 'large', 'wide' and 'long'. The macrophone lives up to its name: it is a horn whose loud, powerful sound cannot be ignored at a distance. They are used on ships and emergency vehicles, as well as on railways. Its signal warns railway users of approaching trains, for example on platforms or at unsecured level crossings. The macrophone, also known as a signal horn, is also used in dangerous situations.
Most trains have two macrophones that are controlled simultaneously – high-pitched and low-pitched. This produces a powerful, dissonant warning sound that has a special signalling effect. According to UIC 644 – the standard that regulates the use of acoustic signalling devices in international rail traffic – the sound pressure level at a distance of 5 metres in the axis of the acoustic signalling device must be between 120 and 125 dB. The frequency of this low tone is 370 ± 10 Hz and the frequency of the high tone is 660 ± 15 Hz.
Modern macrophones are air-operated diaphragm sound machines. This means that a diaphragm clamped inside a box is used to produce sound. The sound is amplified by a horn of a certain size.
