Why do violin bows make a pitch when rubbed against a violin string instead of just a rubbing sound?

184 views

[ad_1]

Why do violin bows make a pitch when rubbed against a violin string instead of just a rubbing sound?

In: Physics
[ad_2]

The way a bow works is straddling the line of grippiness with the string so that pulling the bow causes the string to be pulled along with it, up to the point where the tension in the string lets it slip back, where it grips and pulls again, with the process happening hundreds of times a second.

You’d get a rubbing sound (or probably a screech) if the bow wasn’t gripping the string enough, and was allowed to slide more freely.

You can think of it this way: remember those Pantene commercials where they show the close up of the hair, and it has lots of scraggly points? That’s what the hair on the bow looks like. When you put rosin on the bow (basically baked, processed tree sap), it makes those scraggly points sticky.

The strings have some sort of core (the core varies depending on the type of strings you get), and the metal is wrapped around the core. This metal wrapping causes grooves on the strings.

Those sticky scraggly points then connect to the grooves in the strings, and allows the bow to “pull” and “push” the string, so to speak. This then causes the strings to vibrate and produce sound.

If you have a brand new bow with new horsehair that’s never been rosined, you can get a rubbing noise sometimes, because nothing is helping the hair connect with the string.

That pitch is the rubbing sound, which is modulated by the length and thickness of the string.