General Physics I: Sonometer Lab
Jonathan Laxmi &
Section 14: Monday 5:00-6:50
Experiment Performed: 2/6/12
Lab Report Due: 2/13/12
Objective: The objective of this experiment is to use a sonometer, which is a devic
...
General Physics I: Sonometer Lab
Jonathan Laxmi &
Section 14: Monday 5:00-6:50
Experiment Performed: 2/6/12
Lab Report Due: 2/13/12
Objective: The objective of this experiment is to use a sonometer, which is a device that holds a
single wire under a set tension and detects normal mode vibrations of the wire, to measure how
the normal mode frequencies of metal wires fixed at both ends vary with the length, mode
number, tension, and mass per unit length of the wires.
Description of setup for each part:
We use the sonometer, as pictured below, in each of our four experimental setups. The wire has a
lug with a hole at one end and a cylinder at the other. We use these to hook the wire in and secure
it. We can then turn the knob at the end of the sonometer, which moves the cylinder along the
length of the sonometer. The other end has a tensioning lever used to adjust the tension of the
wire. As shown below, there are five notches to which the string is attached, which can then be
used to adjust the tension. Additionally we can change the hanging mass M with different
masses. To change the points where the wire is fixed, there are 2 bridges which can be moved at
the top of the sonometer. There is also a scale at the top of the sonometer which allows us to
determine the wire length easily.
In each of the four experimental setups, 3 of the 4 parameters (length, mode number, tension, and
mass per unit length) are kept constant with the 4th parameter being varied. In order to measure
the v1’s (lowest frequency mode) most effectively, we placed the detector coil as labeled below in
the middle of the sonometer’s wire.
To setup the FFT display we opened the setup window and changed the number of points from
the default of 128 to 1024. We then changed the maximum frequency to 240 Hz and for the
experimental parts which had frequencies above this, we set the maximum frequency to 480 Hz
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