12/17/08

Post date: Dec 18, 2008 3:23:47 AM

Bell Activity: How do we change the pitch of a musical instrument?

• • Pitch (or frequency) depends on the length of the instrument

    • Longer instrument = lower pitch

    • Shorter instrument = higher pitch

    • True for strings and wind instruments

  • Frequency is determined by boundary conditions

    • Certain conditions at the edge of the string or column of air cause either a node or an antinode in our standing wave at that point

    • Strings - string is held in place at either end, and so must always have a node at both ends of the string

    • Open pipes - air pressure is held in place by all the air around that point, and must have a node at both ends of the pipe

    • Closed pipes - pressure can change the most at the closed end of a pipe, so we see an antinode there and a node at the open end

  • Read 314-318 and do problems 5-10 on 318 (check answers on "handouts" page)