How do police sirens work and how can you tell where they're coming from?

At 5.40am Emergency services attended a two-vehicle crash on Victoria Street, Auckland Central. At this point in our enquiries, we have established a vehicle has been traveling at high speed on Victoria Street West. It has continued down the hill where it has lost control, colliding with a Police car which was stationary at a red light. The crash has caused extensive damage to both vehicles. Police want to make it clear the vehicle was not being pursued, we are releasing some additional footage

3.6M views · 31K reactions | Combination Vehicle Training @ SSS Advance Driving. Emergency braking on dry road surface. No load driving at 60km/h, after applying emergency braking, vehicle still moving 15 - 20 metres before stopping. | SSS Advance Driving | Facebook