Sources of Error in a Speed of Sound Experiment

[mitchy16]

Homework Statement

Determine sources of error which could have affected the results.
Some background information: The lab consisted of playing a tone generated by a tone generator above a standing open-closed tube which had water in it. The first harmonic was measured through a computer system, by determining when the loudest volume was and the tube length where it occurred was recorded.
The experimental setup was a long tube was placed standing up which had water in it, and it was connected to another water cup through a tube, and the water cup was moved up and down in order to determine the L at which the highest volume occurs. There was a tone generator at the top of the tube. The top of the tube was open.
The percent error I obtained was 76% (very high I know, but the TA said it is expected to be that large).

Homework Equations

The Attempt at a Solution

First source of error: measurement increments on the tube are inaccurate
Second source of error: due to human hearing, maybe I didn't hear the highest volume and it resulted in the results being altered.
My TA said the sources of error have to well thought out and not the generic ones, like my first one. I'm not too sure what else I can include. Any help is appreciated!
EDIT: Could one be that there are alternate particles (such as water) in the air and that could cause discrepencies in the speed of sound?

 

[mfb]

The first harmonic was measured through a computer system, by determining when the loudest volume was and the tube length where it occurred was recorded.

Second source of error: due to human hearing, maybe I didn't hear the highest volume and it resulted in the results being altered.

Did you use a computer or your ears to find the loudest point?

The tube will contain some water vapor, but that shouldn't have a large effect. Can the experiment be done with other gases as well? Might some of that still have been in there when you started the experiment?
76% error is huge. I can easily see where 5% to 10% would come from, but 76% basically means you could have guessed randomly.

Technically there is an uncertainty associated to the frequency but that should be negligible.

How did you define the end of the tube? Could this be an issue?To understand your setup better it would help to have some numbers. What was the diameter of the tube? What was the length of the tube at the loudest point? Which frequency did you use? Did you repeat the experiment? Or test other nodes?

 

[mitchy16]

Did you use a computer or your ears to find the loudest point?

The tube will contain some water vapor, but that shouldn't have a large effect. Can the experiment be done with other gases as well? Might some of that still have been in there when you started the experiment?
76% error is huge. I can easily see where 5% to 10% would come from, but 76% basically means you could have guessed randomly.

Technically there is an uncertainty associated to the frequency but that should be negligible.

How did you define the end of the tube? Could this be an issue?To understand your setup better it would help to have some numbers. What was the diameter of the tube? What was the length of the tube at the loudest point? Which frequency did you use? Did you repeat the experiment? Or test other nodes?

Yes, human ears were used to hear the loudest volume.
The tube was approx. 1 metre long and the diameter was approx. 10cm.
The bottom of the tube was closed, and the top was open.
There were 4 different frequencies tested, 400, 800, 1200, 1600, 2000 Hz. Also, it was assumed that it was the first harmonic which was being listened to.
Thanks!

 

[haruspex]

human ears were used to hear the loudest volume.

The background environment could be significant. At a pure frequency, echoes from walls will produce static interference patterns. A small displacement in the position of the ear could lead to a significant change in loudness. Maybe ok if the ear is held very close to the source.

the top was open

At the open end, the tube is effectively longer by about 60% of the radius. See https://en.wikipedia.org/wiki/End_correction.
Please post your data.