Whenever i play the open string it sound good, but when i put my finger to play a note, it squeak or whistle. I tried to play twinkle twinkle little star, when i got to the part when you put your finger to play a specific note, the squeaky and whistle sound appears. I'm new here and my english is not so good, but i'll try my best to communicate to you guys, thanks.
Welcome to the forum. When you play the notes, do you push the string firmly onto the fingerboard?
If you touch the string and then use the bow, the string will squeak.
If you push the string onto the fingerboard and then use the bow, the string will sound correctly.
"It is vain to do with more that which can be done with less" - William of Ockham
"A crown is merely a hat that lets the rain in" - Frederick the Great
Hi Ken and welcome to the forum! It's nice to have you with us.
I agree with what Peter says, but I also notice in myself that it is far easier to play open strings with little to no squeaking and whistling than it is once you start playing other notes, especially in a song, even a simple one like Twinkle Twinkle Little Star because you are now concentrating on hitting the right notes and it is easier to NOT to concentrate on proper bowing technique (i.e. alignment, pressure, etc.) which will produce squeaking and whistling. I am coming up on one year since I started. I just wrote a post on my blog called Back to Bowing Basics. Take a look; it might be of help, too.
Make sure you press the string down firmly BEFORE you start moving the bow. If your bow starts moving too early, it can cause strange sounds. Start by pressing, pause, then move the bow. Over time, you can shorten the pause until it disappears.
Another thing I noticed in my own playing is that the more I concentrate on the left hand, the more my bow hand does strange things. If the bow is moving sideways (even a little), it will affect the sound. If it moves too close to the bridge (which happens far too often to me), it can have a squeaky sound.
Good luck. It gets better!