# Pressure/standing waves

1. Oct 12, 2006

### physics_06er

Hi there

A helmholtz resonator has a resonant freq. of 100Hz. draw graphs showing how the pressure and displacement of the air in the neck vary with time. how would these be different at the position of a listener some distance away...

i can draw the graphs but I'm unsure of the part about the listener being some distance away...??

and the 2nd one is ....explain how a standing wave can be formed by travelling waves, and hence how the frequencies of standing waves on a stretched string are related to the speed at which waves travel along the string?

all i know is that waves would be travelling in opposite directions..canceliing out..? is this even right?...any help much appreciaited

Thanks
physics_06er

2. Oct 12, 2006

### Staff: Mentor

-1- The resonator will have a partial standing wave in it (partial because some of the sound energy has to get out the open end to propagate to the listener.

-2- What is the equation for a travelling wave? What do you get if you combine a left-travelling wave and a right-travelling wave? Also, what is the relationship between the velocity of propagation of a wave on a string, in comparison to the tension of the string and the linear mass density of the string?