At first glance, one soundboard may appear identical to another in terms of grain, color, and density.
But once a string is stretched across it, the truth reveals itself.
Two boards, even from the same tree, can behave differently. One comes alive with rich, resonant tone; another may fall silent, missing the resonance a musician feels more than hears.
This kind of variability is what makes luthiery as much an art as a science.
Traditionally, guitar makers have relied on instinct, touch, and ear to separate ordinary wood from true tonewood. They’d tap, flex, and listen.
That intuition remains invaluable, of course. But if you’re looking for consistency across multiple instruments, data can add a new layer of confidence.
At Pacific Rim Tonewoods (PRT), we believe intuition and science aren’t opposites; they’re partners. By adding measurable acoustic data to what luthiers already know, we help ensure that the “feel” of a board aligns with its performance, giving instrument builders greater control over their instruments’ final voice.
Sonically graded wood does just that.
What Is Sonic Grading?
The BING machine used for sonic grading
Put simply, sonic grading measures a board’s acoustic properties. Instead of relying solely on looks or instinct, guitar makers gather data on how the wood will perform once it’s strung up.
Before a board can be sonically tested, it must meet specific visual and dimensional criteria: it has to be free of obvious defects and thick enough for further processing. If it passes, it’s then acclimated, dimensioned, and tested using a system called BING—short for Beam Identification for Non-Destructive Grading.
Developed in France, the BING system drops a small steel ball onto the wood surface. Sensors record how the board responds to that impact, analyzing its vibrational behavior in real time. From that data, we measure three key acoustic traits:
-
Density: The mass of the wood per unit volume, which influences resonance and responsiveness. At PRT, only boards within the 350–500 kg/m³ range are accepted. Light enough to vibrate freely, but dense enough to support projection and structural integrity.
-
Stiffness (MOE): The modulus of elasticity, or how well a board resists flexing. It’s a key factor in projection and strength. We only accept pieces that fall within ±10% of the average stiffness for their density, ensuring consistent performance and predictable response for luthiers.
-
Damping (Q value): The measurement of how quickly a sound signal decays when we induce a board to vibrate. When a guitar string is plucked, its energy transfers to the soundboard, causing the wood to vibrate and radiate sound. That movement is opposed by the wood’s internal friction; we call it damping.
Scientists express damping as a Q factor, which is the inverse of damping. Basically, low damping is equal to high Q. Low-damping wood tends to radiate sound quite efficiently, all other factors being equal.
The result is an acoustic fingerprint—a precise profile that tells us how a soundboard is likely to behave—before the first cut.
Boards that meet our sonic standards are sorted into Low, Medium, or High density groups. If a board doesn’t make the cut, it’s returned to the general wood stream for other uses.
More than half the wood we test doesn’t qualify as a sonically graded top. That’s how selective the process is.
The above is a sample of 1,700 sonically tested boards, of which more than 50% have been rejected based on our sonic grades. Note the consistency of the blue data points.
The Science Behind the Art
This isn’t just a clever gadget or marketing phrase. Sonic grading is the result of years of careful study, designed to take something as intuitive as tonewood selection and ground it in data without losing its artistry.
Over a five-year period, Pacific Rim Tonewoods partnered with researchers across six labs in Europe and North America to better understand how wood actually behaves acoustically.
The process involved building eighteen guitars under controlled conditions. Each instrument was constructed to identical specifications, with the only variable being the properties of the soundboard. These guitars were then tested in places like Germany’s renowned anechoic chamber. This offered a specialized environment where every vibration could be measured with scientific precision, free from outside noise or interference.
Through this work, researchers isolated three key factors that determine how a top will sound, which we discussed earlier: density, stiffness (MOE), and damping (Q value).
By quantifying the interaction of these traits, we saw that not every spruce top is created equal, and small differences can produce dramatically different voices.
Sonic grading provides a clear starting point. By front-loading the bench with known acoustic values (density, stiffness, and Q), you can select tops that align with the tonal goals of the instrument before carving or tuning begins.
For luthiers, this doesn’t mean artistry is replaced by science. Quite the opposite. It means that intuition gains a foundation in reliable information.
Why Sonically Graded Wood Matters for Luthiers
Sitka spruce (L); Lutz Spruce (R)
So what does this mean when you’re at the bench? Quite a lot, actually.
-
Predictable Tone for Your Personal and Professional Guitar Building:
With knowledge of density, stiffness, and Q, you can choose a board that matches your tonal goals.
Want projection and brightness? A high-density Sitka may be the perfect match for you. Looking for warmth and a quick response? Medium or low-density Lutz could be ideal. Sonic data helps you make intentional selections.
When a client describes the tone they want, sonic data gives you a tool to match their expectations more closely.
-
Consistency Across Builds:
For series instruments or commissions, sonic grading enables you to order boards with similar profiles repeatedly, reducing guesswork and ensuring your builds remain reliable.
The Future of Tonewood Selection
For nearly 40 years, Pacific Rim Tonewoods has been manufacturing spruce into guitar tops for luthiers around the world. Our focus has always been the same: to provide the best product possible. We’re the only tonewood supplier in the US with a deep inventory of sonically graded wood, also available directly to luthiers.
With sonic grading, that mission has reached a new level.
By combining craft with science, we can now give luthiers not only exceptional material but verifiable data about how each piece will perform. It’s the next step in ensuring that every soundboard we ship has the tone, strength, and responsiveness that great guitars demand.
For centuries, luthiers have shaped wood into instruments that sing with a human‑like voice. That art will always remain. Sonic grading tonewood helps luthiers by bringing more consistency and reliability to the process.
Because when science supports craft, the music only gets better.
You can check out our range of Sonically Graded Soundboards here.
