A whistle or horn is used to give the acoustic signal.
A long sound is 2 to 3 seconds, a short sound is 1 second or shorter.

The following acoustic signals are used:

Signal g1: Acoustic signal emergency
Minimum of 5 short tones after each other
Workers need to leave the tracks immediately.

Signal g2: Acoustic signal attention
One long tone
A vehicles will pass in adjacent track

Signal g3: Acoustic signal interrupt activities
Long tone, short tone, long tone
Interrupt the activities. Workers need to leave the tracks.

Signal g4: Acoustic signal resume activities
One short tone
Workers can enter the tracks and resume their activities.