Doppler effect mathematical modeling

I am a high school student and I have decided to do my essay on Doppler effect by gathering my own data and analyzing rate of change in frequency etc. The problem that I’m facing at the moment is that I don’t know how to gather my own data. I am thinking of using a website or an app that produces sound from which I can then measure the rate of change in Doppler effect because if I did measurement outside in the streets it will be difficult to measure rate of change because for example for an ambulance it doesn’t go at a constant speed so it will be difficult to identify rate of change in frequency.

In conclusion, if any of you had done such experiment with sound please let me know what possible website to use to do such measurements or give me some inspiration from which I can carry out this experiment from home or outside that would give me the ability to analyze data.

(Sorry everyone if I am not being clear but I am struggling and anyone’s help would be appreciated)