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Hear what the Doppler effect does

For these links, imagine here that the sound is being generated by a speaker, which is not moving, and you are moving either towards or away from the speaker at a certain speed.

The speaker plays a 500 Hz sound. Hear it.

 If you move towards the speaker at... If you move away from the speaker at... ...10 miles per hour, you would hear this instead. ...55 miles per hour, you would hear this instead. ...100 miles per hour, you would hear this instead. ...10 miles per hour, you would hear this instead. ...55 miles per hour, you would hear this instead. ...100 miles per hour, you would hear this instead.

The speakers plays a 1000 Hz sound. Hear it.

 If you move towards the speaker at... If you move away from the speaker at... ...10 miles per hour, you would hear this. ...55 miles per hour, you would hear this. ...100 miles per hour, you would hear this. ...10 miles per hour, you would hear this. ...55 miles per hour, you would hear this. ...100 miles per hour, you would hear this.
(Hint: The goal here is to compare the sound the speaker is playing versus the sound you would hear. For a given speaker, rapidly click back and forth between its Hear it link and a you would hear this link.)