# 2 more problems with sound.

1. Jan 21, 2006

### jrd007

1) An unfingered guitar string is 0.73 m long and is tuned to play E above middle C (330 Hz). (a) How from from the end of the string must a fret (and your finger) be placed to play A above middle C (440 Hz)? (b) What is the wavelength on the string of this 440-Hz wave? (c) What are the frequency and wavelength of sound in air at 20 degree's C by this fingered string? Answers: a) 0.18 m, b) 1.1 m c) 440 Hz and 0.78 m

I am really stuck. All I can figure is that you incorporate L = v/2f.... and f = v/wavelength.... help me, please.

2) How many overtones are present within the audible range for a 2.14-m-long organ pipe at 20 degree's if (a) it is open (b) it is closed. Answers: a) 248 overtones, 249 overtones

What I thought you could do was v/2L and v/4L.... 343/(2 x 2.14) = 80 and 40... not correct.

2. Jan 21, 2006

### Astronuc

Staff Emeritus
See if these examples help - http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l5b.html [Broken]

To get a higher pitch, one has to shorten the length of the string.

Try f1 * L1 = f2 * L2, where f is frequency, and then the finger is place x = L1 - L2, and I think you can handle it from here.

Last edited by a moderator: May 2, 2017
3. Jan 22, 2006

### jrd007

So I would use.

.73 m x 330 Hz = L2 x 440 Hz.

L2 = .547 not the same as the answer 1...

4. Jan 22, 2006

### jrd007

Anyone else have a suggestion?

5. Jan 22, 2006