brightness/warmth measurement

[jjhturbo]

Is there a tool that can be used to objectively measure a guitar's brightness/warmth? Sorry, this may be a dumb question -- but I am not a sound expert. Just trying to see if I can do a side by side objective comparison of various guitars and/or strings.

Not sure if it's as simple as taking measurements on a frequency meter.

[musicman1951]

I am not aware of a meter that measures warmth. Everyone lands where their ear likes on that continuum. Pick what you like. You don't have to be an expert, you just have to recognize what pleases you. If you're not too fussy, all the better.

[Silly Moustache]

Originally Posted by jjhturbo

Is there a tool that can be used to objectively measure a guitar's brightness/warmth? Sorry, this may be a dumb question -- but I am not a sound expert. Just trying to see if I can do a side by side objective comparison of various guitars and/or strings.

Not sure if it's as simple as taking measurements on a frequency meter.

Hi, firstly there is no dumb questions if you genuinely don't know, and want to know the answer.

There are various similar questions that may be pondered regarding music, musicians, and instruments, not least the questions I see on another forum as to which of two or three musiacians are the best.

Of course, there is no absolute measure of "best".

Similarly, the answer to your perfectly valid question is .... no.

I say that because, surely, brightness and warmth, are subjective judgements?

I guess there could be some sort of audio analysis of the volume of each string and compare them, but is that all there is to tonal quality?

People talk of the "Martin" sound, which only really emerged when they abanded the notion of balanced tone.
Bill Collings decided that he would make guitars that would be evenly balance across the strings.
Many people "conditioned" to the Martin sound hear Collings guitars as bright, or even trebly.

Many ghear Taylors similarly ... I think they sound trebly and thin too, but many love them.

It's just about perception.

[KevinH]

Yeah, you might think it's possible. Out of curiosity, a few months ago I started recording single string plucks and strummed chords on some of my guitars to see if I could see what it was that made them sound different to me. You can use a recording device (your phone, a usb mic plugged into you computer, etc) to make a brief recording, then use free software like Audacity or Sonic Visualizer to plot a frequency spectrum - which basically shows you the amplitude of the signal vs frequency. Or you can plot a spectrogram, which shows the spectrum as a function of time. In either case, comparison of those plots for two different guitars should, in principle highlight the differences and maybe show you warm vs bright.

But it's more complicated than that. There is a whole field of study (physchoacoustics) that considers how humans perceive sound. Perhaps Alan Carruth will chime in. In other threads, he has talked about his experiments where people listen to two of his nominally identical guitars. But due to the unavoidable differences in pieces of wood, people find them to sound different - even though much of their frequency spectrum plots look identical at frequencies below 1 kHz. If you take a few spectra you'll see that things get really complicated above several kHz, where there are many resonances that interact with one another, and it becomes's harder to figure out.

If you like to tinker with things, it's easy enough, and instructive to try. Maybe if you compared what you perceive to be a bright guitar against a warm one you'll see the trebles standing out some. I had a little success when comparing one of my guitars that my ears say has a more articulated sound than another - the peaks in the frequency spectrum of that guitar were generally narrower. But in general, it seems that finding correlations between what you hear and what the computer hears is fuzzy to say the least, and the qualitative terms we have to use to describe sound, like brightness, warmth, boxiness, etc. can mean different things to different people.

[cliff_the_stiff]

I wonder if we are looking at it backward.
maybe sensors in various areas of the guitar body could sense certain measurements of frequency and strength of those vibrations-
Like nodal measurements, and then the scientists can observe the tonal qualities they perceived to be associated with the guitars tone. It would be somewhat subjective, but a large sample group could even that out.
Then look for measurements that are similar between guitars with similar perceived tonal observations.

[Gordon Currie]

The 'how' is certainly doable. Sound level measurement tools could do this easily.

But the elephant-sized problem is defining what bright and warm are.

Are they mutually exclusive, or is there some overlap?

Good luck on that.

[jpmist]

Originally Posted by KevinH

If you like to tinker with things, it's easy enough, and instructive to try. Maybe if you compared what you perceive to be a bright guitar against a warm one you'll see the trebles standing out some. I had a little success when comparing one of my guitars that my ears say has a more articulated sound than another - the peaks in the frequency spectrum of that guitar were generally narrower.

I went down that road a year or two ago, seeing if I could find an objective measurement to confirm what I was hearing. What you're seeing below is the exact same point in time after a strummed E chord. The OO-05 (top) is a small bodied 12-fret Larrivee with spruce/mahogany and the Taylor 322 is a hogtop/blackwood 12-fret. To my ear, the 322 has a much darker tone than the brighter OO-05 which I think the graphic confirms as the 322 has a lower level of higher frequencies. But so much depends on recording methodology as well as interpretation and I didn't get much further with it.

[Alan Carruth]

It does seem to me that what I think of as 'brightness' is a multi-dimensional thing. It involves not just the spectrum, but also how the sound develops over time. Some 'warm' sounding guitars seem to actually have more output in the treble than others that are 'brighter', IMO. Nothing about the guitar is simple.

Some years back, on another list, somebody described an experiment that was done with tone descriptors at a conservatory. They asked people to name terms they would use to describe the tone of a violin, and whittled the resulting long list down to a few of the most common ones. They made careful recordings of the same player performing the same short piece of music on different violins, and played them back to people in random pairs through ear phones. Listeners were asked to rate the two instruments in terms of one of the tone descriptors: " Which is 'brighter', A or B?", and so on. The results were interesting.

A)Everybody seems to use the terms differently. Your 'bright' might be my 'nasal'.

B) People use the terms consistently: if violin 'a' is 'clearer' than 'b', and 'b' is 'clearer' than 'c', they will always hear 'a' as 'clearer' than 'c'. But the most interesting was;

C) If a particular instrument had some quality that a listener did not like, they would be unable to rate it on any other quality. If you don't like 'tubby' sounding instruments, and a particular one strikes you as 'tubby', then you can't say whether it's more or less 'even' than another.

Under the circumstances I don't think it's possible to come up with any objective way to place instruments along a 'brightness/warmth' continuum. You could do that for yourself, but you may not find many people who would agree with your ranking.

[varve]

Hmmm. Well, here goes. There IS a measurement that can be applied to a digitally recorded tone that does correlate with, and thus “measures” brightness. It is known as the “spectral centroid”, and it is really a simple concept. If we add together all of the amplitudes in a spectrum, as if we were numbers, then it can be seen as simply the Average , or “center” value of the spectrum. If the center is weighted toward a higher frequency, then that overall recorded tone is characterized as “bright” a characterization that is broadly agreed-upon by listeners. It gets more complex of course, because Fundamental frequency and intensityalso should be added in, but really it’s all easy to the computer program.

Engineering students and acousticians use a software Package, a language really, called MATLAB, which has housed within it musical analysis sotware that kicks out such measurements. I donÂ’t know whether anyone has ever compared guitar tones with it, however to answer the interesting question you pose. If interested, the acoustical society of America has a musical Instrument wing that dates back to Carleen Hutchins in the 50Â’s. A quick search on Google using terms like guitar and spectral centroid may help. Good luck, let let us know what you find!

[wguitar]

It really comes down to what sounds and feels good to you. Sure, there are scientific ways and tools to measure/compare/evaluate guitar tone, but (as has already been noted) one man's warmth is another person's bright. Not to mention, a guitar's tone will be influenced by multiple variables like humidity, pick and string selection, playing style, flat picking vs. finger picking, and so forth. I enjoy my guitars by not characterizing them but rather appreciating each one for the sound and personal joy (for me) they produce. But that just me. YMMV.

Cheers!

[Gordon Currie]

Verve - interesting about the spectral centroid. It does appear that would work for a rough yardstick of brightness perception.

I think warm is an order of magnitude more difficult to define.

[hamburg325]

My take is that higher output in the mids and lows, along with more overall (2nd order) harmonic overtone content, will create a "warm" tone that takes the bite out of even very bright trebles.

[virob]

Could something be learned from the stereo worlds methods for measuring distortion? Or how a distortion peddle works? Is warmth just another term for a certain type(s) of distortion? Tube amp vs solid state is another example. A guitar is a little different because it is an instrument making the sound vs the above examples that are reproducing a sound, but to principle should still apply I would think. A plucked guitar string includes the fundamental plus overtones/distortion. The amount and type of this distortion determines the amount of warmth. The tricky part is that there are several different types of distortion being created at different levels, the sum of which we hear.

[jjhturbo]

Lots of good points and info.

I agree that the terms "brightness" and "warmth" are subjective...and the interpretation of these words to describe sound may (and do) differ from person to person. But, to phrase my question a different way (and in the same vein as what Silly Moustache and others alluded to)....if we compare the classic Martin tone versus the Taylor tone, without using any adjectives to describe what we hear...the point is they are obviously very different. The question really is -- is there a relatively simple way to objectively measure/quantify what that "different" is? From what I'm reading here...it may not be as simple as I thought. Interesting.

[Alan Carruth]

So basically it's the 'tonal center of gravity': if it's more toward the treble end it's 'bright' and if it's lower it's 'warm'?

I once ran an impulse spectrum of a plywood guitar that a friend had retrieved from the trash with a lifting bridge. He put a new one on, and the sound, although well balanced, was 'flat'. It had more output in the high treble than I'd have expected, but the line itself was also flat: there were no peaks or dips in the output to speak of. I suspect it was due to the high damping of the plywood top: it was light and stiff enough to produce a decent average output in the high end, but the resonant peaks were largely damped down

It seems to me that, aside from such spectral measures, you also need to include some time-domain stuff. In particular, how does a sharp 'attack' factor into 'brightness'? It seems to me that it does: I've seen guitars that had strongly bass-balanced spectra that still had a 'bright' edge. Then again, that may just be my own idiosyncratic take on what 'bright' means.