Does low humidity affect tone?
 

It is well known that HIGH humidity can make most guitars sound like they have socks stuck in the soundhole; muffled, lifeless and uninspiring. As someone that lives in a high humidity area, I know this too well.

But what about the other end of the spectrum, low humidity? Does it impact tone when it gets too low?

I've heard it said to be so. The "action" becomes lower as the humidity lowers. Many guitars that were set up in more humid conditions will develop a buzz. I've heard it said that guitars sound best -- loud and sparkly -- when they are almost too dry.

I hear my guitars sounding their best after being in about 42% to 45% Relative Humidity for a few days. I don't like the tone of my guitars when they've been in 50% to 55% RH for a few days. From my experience, 42% to 45% RH is still a safe RH range in which no damage to guitars will occur and I endeavor to keep my RH at about 45% which, depending on the season, is easy to do with a full-room humidifier and a full-room dehumidifier.

Above 55% for even a day makes mine sound awful.
I’ll go with the 42-45% range, but I’ve never had any issues with it being as low as 35% for a few days.

There are so many things that affect tone that I doubt I could single out humidity as the single culprit. But some have extremely sensitive hearing and can read the tone of a guitar like a book. That's not me. Any changes in tone I generally attribute to me, and that includes buzzing. I can usually take care of buzzing by paying more attention to my fretting.

I would not argue though that humidity isn't one factor. I believe that temp and humidity often times join together. I have a wall hanger right below a widow in my basement and in the winter it is ten degrees colder right there. Whatever guitar happens to be hanging there will be wonkier than the one two foot over when I first pick it up. Also, if I measure the humidity right there it is different than three feet to the left of it. But that is what relative humidity is, isn't it, humidity relative to temperature?

Yes. They sound amazing!

I’ve heard luthiers say that a guitar will sound it’s best right before failure.

I’m not going to test that theory, but keeping them in the low 40’s is where it’s at for me.

I've played a few guitars that suffered from low humidity. My personal experience was that they sounded thin and metallic. It was almost as if the tone of the wood had been stripped away to some extent and you were just getting the metallic sound of the strings.

I 2nd Kriso's comment - If I let my acoustic dry out during winter it sounds terrible till I put it in a case with something damp for a week or so. On the other hand my plywood Godin Kingpin does not seem to mind being left out on a stand all winter.

I like the way my guitars sound at about 42% humidity. They are sort of bright and ringy and very responsive.

Bob

My violin making teacher used to say that there were two kinds of violinists: the ones who cussed violin makers in the summer, and the ones who cussed them in the winter.

Although there are things about high humidity itself that tend to hurt the sound, much of the way an instrument sounds depends on how everything works together. High humidity tends to alter 'wood' resonances and 'air' resonances in opposite ways, so if they line up right at one humidity they will not be lined up when it changes.

Traditional makers often stopped work, or did things like make trim and put on finish, when the relative humidity was not right. These days many makers pay pretty close attention to humidity, and work hard to control it so that they can be productive all year 'round and have fewer warranty returns. My understanding is that wood tends to be most stable at around 50% relative humidity, and since structural issues are more problematic at lower humidity, many makers try to keep it a bit below 50% most of the time. So that's likely to be the humidity level that will sound best, more or less.

Lower humidity does reduce the density of the top a bit, make it a bit stiffer and reduce the 'damping' of the wood. All of those are considered to be 'good' for sound, so it's likely that many guitars would sound better when the humidity is on the low side. OTOH, back when I did more repair the busy season for things like top cracks and lifting bridges was late winter, after the central heat had had plenty of time to dry things out. A guitar with the bridge hanging off it by the strings tends to lose much of its tone and response.

I think the humidity effect on tone is far worse for archtop players. The tops on archtops are much thicker and more stiffly braced to begin with, than flat tops. Of course, from the on-set, archtops get their distinct tone and rapid note decay from this design, but man, when the humidity gets high in the Summer, tone really suffers :(.

I'm often amused at what people can get funded to study. I was reading a paper this morning that describes some controlled experiments in which the authors looked at how the sound of a guitar changes with relative humidity. They impulsively, and remotely, struck the 3 lower bass strings of a steel-string guitar over a period of 3 days while the RH varied (50% to 70%) in the chamber the guitar was in. They periodically measured the mass of the guitar and recorded the sound. They found a consistent difference between the sound of the "wet" guitar and the "dry" one - both from analysis of the sound spectra, and from perceptual tests using both musically-trained and non-trained subjects. Interestingly they found a roughly 9 hour lag between a change in RH and the sound and mass of the guitar (the mass only varied by 2 gm and it appears the resolution of the scale was only 1 gm, so that's a bit sketchy). I've often wondered how long it takes a change in RH to show up in the guitar. So that's one data point. This doesn't tell anything about how "good" the wet vs dry guitar sounded, since they only hit the open D, A and E strings, but at least says there is a difference that can be detected by computers and we humans.

I never notice any humidity-related differences in my guitars. My music room was at 38% when I went up there today - the one guitar I played sounded the same as it always does to me. I'm not going to turn up the humidifier unless it goes down a few more notches.

Yes humidity affects the sound especially on a solid wood guitar. On a guitar with laminated B/S it's much less apparent.

I think they sound a bit better and more resonant when a bit dry - say 40% to 45%. I don't really let my guitars get below 40%, and usually not below 45% for long, so I can't say how a chronically dry guitar would sound. I'd imagine if you started to get into the buzzing and low action range that it would sound pretty bad.