Cold Guitar - Strings go Sharp

[mjones32]

So if I leave my steel strung guitar overnight in my cold basement, it goes out of tune on the sharp side.

Now if I want to manually tune my guitar sharp, I have to tighten the strings = i.e. put energy into the system and do work.

So where does the energy come from to do this in a cold room ? What energy is being converted from what to make the strings tighter ?

 

[mack_10]

"sharpness" is due to diffference in contraction rates of steel strings and body of the guitar, steel contracts more increasing tension raising pitch.

It is not so much energy coming from the room as thermal energy leaving the guitar.

 

[Astronuc]

So if I leave my steel strung guitar overnight in my cold basement, it goes out of tune on the sharp side.

Now if I want to manually tune my guitar sharp, I have to tighten the strings = i.e. put energy into the system and do work.

So where does the energy come from to do this in a cold room ? What energy is being converted from what to make the strings tighter ?

Thermal contraction of the metal (steel) strings leads to an increase in tension in the strings. The pitch is slightly higher - much the same as if one turned the tuning key to increase the tension. As the string warms, the tension decreases, and so does the pitch/frequency.

 

[Andy Resnick]

So if I leave my steel strung guitar overnight in my cold basement, it goes out of tune on the sharp side.

Now if I want to manually tune my guitar sharp, I have to tighten the strings = i.e. put energy into the system and do work.

So where does the energy come from to do this in a cold room ? What energy is being converted from what to make the strings tighter ?

As everyopne else said, it's due to thermal contraction- specifically, that the thermal contraction of the strings is greater than the contraction of the guitar body/neck/pegs, etc.

This could be an interesting experiment, if you have decent temperature control- can you precisely measure how much the pitch changes? Does it change the same relative amount in each string? etc. etc.

 

[Andrew Mason]

So if I leave my steel strung guitar overnight in my cold basement, it goes out of tune on the sharp side.

Now if I want to manually tune my guitar sharp, I have to tighten the strings = i.e. put energy into the system and do work.

So where does the energy come from to do this in a cold room ? What energy is being converted from what to make the strings tighter ?

Similarly, ice expands moving rocks on shores, bursting beer cans etc.

The answer is not as easy as it might seem. The energy stored in the string increases as the tension increases. This is because, as others have said, the natural length of the steel string decreases with temperature at a greater rate than the guitar, so there is an increase in the stretch of the string ie. actual - natural length. Assuming the string follows Hooke's law, the energy stored in the string is .5kx^2 where x = stretch (actual - natural length) and k is the spring constant of the string.

The answer must be that some of the internal thermal energy in the string is converted into mechanical potential energy in the stretched string.

AM

 

[yungman]

I think the contraction cause increase tension is well covered by everybody. My comment is...


Don't leave the guitar in the cold!...Unless it is a cheapy that you don't care! I was a serious guitarist for over ten years in my younger days and I still have my Les Paul from the older days and two Strats. I never subject them to extreme temperature. You might ruin the body.

Another possibility and likely is the trust rod in the neck contract in cold temperature. When you tighten the strings, they tend to pull the neck forward and bend the neck forward. So they put in a trust rod with a nut at the end to bend the neck back by tightening the bolt of the rod. This rod pull the neck the other way. This is how you adjust the straightness of the neck when you change strings' gauge. When the rod contract, it bends the neck the other way and cause the string to go sharp. The strings are exposed to air, as soon as you take it back into the warm room or start playing, the strings will warmup to normal temperature in no time. But the trust being inside the wood neck, still remain cold for a long time and you notice the strings are all sharp.

In fact I just adjusted my guitar trust rod a week ago and notice the strings went sharp without change of temperature. Look at the head of you guitar, you usually see a plastic cover. Removing that will expose the trust rod adjustment. Fender is a little different, there is a hole and you stick the Allen wrench into adjust it.