Is the Air Resonance Frequency of a guitar of any significance to you as a player?

[TRose]

I’ve recently become aware of the “Air Resonance Frequency” (ARF)of guitars. I’ve seen the ARF listed as one of the specs of some guitars that are for sale.

Do any of you consider the ARF of a guitar when purchasing or do you desire a particular ARF over others? Is it more commonly considered of significance in finger style or classical guitars? Or is it just of academic interest?
Asking the Luthiers: Is there a target ARF for any particular build and does it change with varying desired end result characteristics?
Thanks,
Tom

[ljguitar]

Originally Posted by TRose

…Do any of you consider the ARF of a guitar when purchasing or do you desire a particular ARF over others?

Hi Tom

Never entered my mind before nor after purchasing my guitars.

I have played amazing guitars, and own three which please me (and others) immensely.

[TRose]

It never entered my mind ,as well. But then I was unaware of it all together.

I do wonder if guitars I find pleasing have a particular ARF. But just a curiosity. If they do then that could be one more thing to add to the list of desired “specs”, I presume.

Since some guitars have them listed in their specs I assume someone wants to know that information on the front end. If so, why? What’s the practical significance?

[Mark Stone]

I've never heard of ARF -- This thread is gonna be an interesting read!

[Beakybird]

I've never heard of this spec. What is a desirable ARF?
I've heard of BARF. That's the frequency at which the audience gets sick of hearing you play.

[Marcury]

I only care about ARF when the guitar's a real dog.

[Italuke]

It's another name for the Helmholz frequency, the natural frequency of the air mass of the body of all hollow stringed instruments (as I remember, someone else can look it up...).

[Mark Stone]

Originally Posted by Marcury

I only care about ARF when the guitar's a real dog.

Lol we got all the way to post 6 before the barking joke! I had expected it earlier

[Tico]

FWIW, I found this on the FAQ section of Kent Guitar Classics.

13) What is ‘Body Air Resonance’ in a guitar?

Guitars, like many other stringed instruments, are a box of air with an air column at the soundhole. Such a construction has a musical pitch /a frequency at which, as a whole, it will vibrate. The typical, or let’s say, many, modern-day classical guitars tend to have a pitch somewhere around G to G#. To test this, if you hum quite loudly into the soundhole, starting at the pitch of the open 5th string – A, and then drop the pitch of your humming, sliding chromatically down, you should feel a pitch or note at which you can feel and hear the body, back and sides vibrate – and as you go down further, you will go past that pitch and it will stop again. This is what I refer to as the body air resonance frequency.

Where this pitch lies, depends on many factors including, the woods the guitar is made from, the area and depth of the body, the stiffness of the back, the stiffness of the sides, the diameter and precise location of the soundhole, the stiffness of the edge of the soundhole, the shape of the back bars, top bars and fan-struts, the construction type of the soundboard, the weight and shape of the bridge … and many, many more things. In my view, the air resonance frequency tells a lot about the sound character of the guitar. Many older guitars, like Torres, Enrique Garcia and Simplicio, have a deep, old-world sound – and commonly have an air resonance down at E or F. Many guitars of Herman Hauser I & II had resonances around F to F#; sounding much deeper than many guitars pitched at G or G#. A few Hauser I’s, made in 1940 had a resonance down around E flat; much deeper than most and perhaps untypical. On the other hand, some guitars that are more stiffly-built have air resonances up at A or B flat – and therefore tend to be trebley, bright and probably lacking depth of bass. Do note that many guitars will have a resonance pitch that is not exactly on the note of a scale; it may be halfway between G and G#, or just below or just above a particular note – this can be advantageous.

The body air resonance is different from the guitar’s tap-tones – of which there are many. If you tap the guitar top at the bridge or just an inch or 25 mm below the bridge – using a tambora with the fleshy part of your thumb, you should be able to hear a tone (you need to damp the strings of the guitar at the neck when doing this). You may hear more than one tone, but the more obvious one is usually referred to as the tap-tone of the top. I observe that in 95+% of classical guitars, the body air resonance is usually one semitone lower than the tap-tone of the top (an octave and a semi-tone actually) – so, if the tap-tone is G#, the air resonance is likely to be G. I can’t explain why that should be, but check it yourself; I have done it hundreds of times and it is usually so.

14) Why is body air resonance important or relevant?

There are so many classical and flamenco guitar makes around the world that have different sound character. One of the obvious differences is whether they are deep and rich – or bright and trebley. The deep and rich ones will have a low resonance frequency; the bright, trebley ones a higher resonance. So when buying a guitar from a long way away, if I know where the resonance is, it tells quite a lot about the general sound character. Some makers go through periods when their instruments are lighter and deeper in sound – and periods when the opposite is true. I believe this can be said of Fleta, Friederich and Hauser guitars. Some people like deep-voiced guitars; some prefer brighter instruments. If you know where the air resonance is, it tells you a lot straight away.

Another example – as a player, I prefer to avoid guitars that either have a strong tap-tone on A or an air resonance on or too near A. I find them usually to have an unpleasant open 5th string because when you play that note, the guitar body reacts explosively and produces a ‘wolf-note’ on A – which is such an important and frequently-used, open string bass note. Also preferring deeper-voiced guitars these days, I feel guitars with an A-resonance are generally too bright for my personal preference – that is not to say they are bad or worse than something else; it is just what I prefer – and others may prefer something different from me.

Another aspect relates to buzzes. All guitars buzz somewhere; particularly when new. They are more likely to buzz on those notes that relate to the soundboard tap-tone or the air resonance. Many guitars are a bit rattley when you play the 6th string G or G# strongly (if they have an air resonance on G – G#) – and the same thing, often more annoying, can be the equivalent notes on the 4th string, where the action may be slightly lower if there is curvature in the frets or fingerboard. Again if you understand where the air resonance is on your instruments, it can guide you to understand on which notes you may need to play less forcefully and why.

[printer2]

Not going to complain about the Kent explanation, some of it is ok, some not sure if I agree. As a player, if you like the sound of the guitar that is all you need to know. It really does not tell you that much, varies with the size of guitar, I have thought it useful to know as a builder, but then there are other resonances that you would want to know along with it.

[TRose]

Thanks, Tico!
Printer, I agree that if a guitar sounds good then all is well. I’m just on the steep part of the learning curve when it comes to guitars and enjoying lots of rabbit holes.

[Rick Jones]

If my Avalon L32 is in its stand in my den and I have doors and windows open, the strings start singing harmonics if anyone or anything outside of the house makes a D note of any kind that it can ‘hear’.

As I am so fond of it, I’d sing a D into any potential new guitar and if it did similar — and to a similar degree — I’d be more likely to buy it.

Not sure if that qualifies.

[Michael Watts]

it matters to me to know what the top, sides and back have been tuned to and what frequencies the instrument is most sensitive to.

[Peter Z]

Tico, thank you for posting this very interesting stuff. I always wondered why there is so much talk about 'tap tuning' and almost nothing about this Helmholtz effect, that must have at least as much influence on the sound like the resonance frequency of single elements, even the top.
If you ever treated a room acoustically you know exactly how huge the Helmholtz effect can be.

For a player, all that is meaningless, he/she likes a guitar or she/he doesn't.

But that is for already existing instruments. A builder, creating an instrument, can use that knowledge to his, and at the end, the players advantage.

To me, it's just a bit additional knowledge. Not important but nice to have. :-)

[Bob Womack]

Well, considering that an acoustic guitar is a combination of a Helmholtz resonator and a sympathetic planar resonator (the top), the ARF of a guitar is of infinite concern to me. However, I have never once in my fifty years of playing an buying guitars been offered that data on a guitar, so my interest has been confine to a certain detached scientific curiosity* and the intuitive world of perception.

Bob

* My father was a scientist and a very, very curious man who loved to study, well, everything. I'm afraid I inherited his curiosity. It drove my late in-laws to the edge at times.

Speaking of which, what is the airspeed velocity of a laden African swallow?