# Superpositon and Standing Waves problem

1. Feb 6, 2010

### weezer13578

1. The problem statement, all variables and given/known data
A child has an ear canal that is 1.3 cm long. At what sound frequencies in the audible range will the child have increased hearing sensitivity?

2. Relevant equations
for open-closed tube, f= m(v/4L)

3. The attempt at a solution
I need two frequencies since the question is asking for a rage in which the child has increased hearing sensitivity. So I thought for an open-closed tube, I could use f= m(v/4L) where m=1 and 3. But my answer does not work. How do I know what nodes (m) to choose? Please help.

2. Feb 6, 2010

### weezer13578

I have previously found 6600 and 2.0*10^4 using m=1 and 3, and this range didn't work.
Could anyone help?

3. Feb 6, 2010

### Stonebridge

The question is asking for specific frequecies in the audible range; not a range of frequencies.
The method is correct. 6600Hz is in the audible range (quarter wavelength). The next resonance should be at 3 times that value. (3/4 wavelength)
Audible range goes up to 20000Hz typically.