Play a sound if text field meets criteria

I've had no issues playing sound files through the Action menu. I have several .wav files that are "on focus" and what have you, but I'm having issues with the javascript verifying the textfields.

For an even more basic example, when I use the below javascript "on blur", the alert pops up regardless of the value of the field.

var i = this.getField("Initials");

if (i = "AM")

app.alert("AM");

What am I missing that is causing it to trigger on blur without checking the "if" statement?

I've also tried using validation like:

var n = event.value.indexOf("AM");

if (n == -1) { // substring not found

    app.alert("Not AM");

    event.rc = false;

}

else {

    app.alert("AM");

    event.rc = true;

}

And this will correctly pop the "Not AM" alert, but not the true one.