Ambient sound, also called natural sound, is basically the background noise in a given context.

For example, a person is walking through the busy streets; in that case, the person will hear the buzz of traffic and the chattering of the crowds among many other noises. All these noises make up the ambient sound.

In another scenario, if it is raining heavily, the sound of the rain and the sound of the passing water, and the sound of the lightning will compose the ambient sound.

So, the sound of the crowd, the rain, vehicles honking on the street, birds chirping on the trees, sound of the waves on the shore and others such are considered as ambient sound.