Pinyin d and w

Define onomatopoeia to describe the sound of police cars, ambulances, etc.

Make sentences, beep, beep, beep, beep, beep, beep, beep, beep, beep.

The siren of the police car is very urgent and there is no interval. The siren of a police car is short, crisp and urgent, and the frequency like "wow, wow, wow ~" is 2~3 times per second. Give people a warning and a sense of oppression against criminals.

Ambulance sounds longer:

Similar to the form of heart rate pulse, the frequency of "no mile ~ no mile ~" is once a second. Mainly highlights the sense of urgency and urgency. The sound of the fire alarm takes the longest time, especially the alarm sound of "meow, meow", the frequency is about three seconds. The voice is very low, which makes people feel that the incident is serious and urgent.

American standard sirens are used in China, but it is stipulated that police cars, fire engines and ambulances must use uniform tones. I can't remember the official name of each sound. The name on the alarm shall prevail! The police car is the most urgent, and the continuous prompt tone indicates that it is urgent. The sound name is Yelp. Some fire engines are similar to air defense alarms. The closer they get, the farther they spread. The sound name is "wailing". The purpose of the ambulance is to create a "sense of drop" through the alternating sound of high and low, reminding traffic participants to make way for the ambulance as soon as possible. Tone names "high/low" and "high and low"