Tina is waiting at the bus stop. she sees and hears an ambulance as it approaches and passes by her. which two changes in the loudness of the siren does tina hear?

When ambulance approaches her, the loudness increases and when it passes by, the loudness decreases.

Explanation:

Loudness of the wave is determined by the amplitude of the wave. More the amplitude, louder will be the sound and vice-versa.

As, the ambulances reaches Tina who is standing at the bus stop, the amplitude of the sound increases which increases the loudness.

And when the ambulance passes by, the amplitude of the wave starts to fade away and the loudness of the sound decreases.

These two changes were experiences by Tina when she heard the loudness of the siren.