Compare individual pieces before the build begins.
Standardize dimensions where practical, tap the board, and compare modal frequencies alongside stiffness to weight, density, species, and the rest of the material record.
AcouSonix™ / FREQUENCY HAMMER / FOUNDERS EDITION
Instrument voicing begins with data collection.
The AcouSonix Frequency Hammer is a purpose built instrument making tool that performs a dominant frequency analysis on whatever you strike. It uses FFT analysis to identify the strongest frequency response, then immediately displays that result in hertz and as the closest musical note.
There is nothing mystical about what the Hammer does. It was engineered around steel string guitar work, but the same measurement has proven useful on violins, archtops, banjo heads, drums, isolated top and back plates, individual braces during tuning, raw tonewood, and other resonant parts. Its value is speed and repeatability. A builder can make the same frequency check throughout the work and keep one more variable attached to the build record instead of relying on memory alone.
DOMINANT FREQUENCY
132 Hz
C3 +1.5 Hz
MEASUREMENT METHOD
How the measurements are collected and interpreted.
The first presentation covers the Frequency Hammer measurement process. The second moves into FFT analysis, overlays, peak information, and the way those observations can be compared as the material or instrument changes.
01ExciteTap the part consistently.
02MeasureRead dominant frequency.
03DocumentKeep the result with the build record.
04CompareChange one variable, then measure again.
FREQUENCY HAMMER WORKFLOW
How to Use the Frequency Hammer
01/06
FFT ANALYSIS WORKFLOW
FFT Analysis in Lutherie
01/09
WHAT THE NUMBER MEANS DEPENDS ON THE CONTEXT
Frequency data is most useful when the context is consistent.
It is easy to treat a single frequency as a target or a verdict, but that is not how AcouSonix approaches the measurement. A frequency reading is one part of a larger material record. By itself, it does not tell you whether a top, back, or piece of tonewood is good. Its value comes from knowing how the reading was collected and what happened to the material afterward.
When support, tap location, dimensions, and measurement sequence are kept consistent, the readings become comparable from one stage to the next. Over time, that record gives the builder a clearer picture of how particular materials and construction choices relate to the sound and feel of finished instruments.
The builder remains the decision maker. AcouSonix is intended to add a repeatable reference to the process, not to replace experience, listening, or judgment.
Track how the top changes as structure and mass are added or removed.
Measure the free plate, braced plate, and later the assembled instrument. The useful information is not one target number, it is how the response moves as you work.
Measure the back with the same consistency used for the top.
Track back-plate resonance and compare it against the top and the assembled body. A consistent process lets you study relationships instead of isolated readings.
Keep a repeatable record of the completed instrument.
Top, back, and air readings become a repeatable signature for the finished guitar, something you can save, compare, and use when the next instrument comes across the bench.
BUILD A RECIPE YOU CAN RETURN TO
A consistent workflow can become a repeatable tonal recipe.
When frequency is collected alongside stiffness, density, dimensions, and the other material information that matters to the build, the measurements begin to form a useful record. If you also support plates the same way, tap them in the same locations, and carve braces toward repeatable frequency relationships, you can reduce variables from one instrument to the next and learn which combinations consistently produce the response you want.
The goal of the Frequency Hammer is not to assign one correct sound to every guitar. It is to help you identify your own voice, understand the measurements associated with it, and make that result easier to reproduce. Your instruments stop being a moving target, and players who respond to your work have a better chance of finding that same character again.
USING THE FREQUENCY HAMMER
Keep it ready, then measure without interrupting the work.
Initial setup is intentionally simple. Take the Hammer out of the box, connect it to USB C, and begin using it. There is no power button and no measurement menu to work through. The Hammer is designed to be stored on charge, with overcharge protection built in. When you need a reading, take it off the charger and start tapping. It can also be used while it is plugged in.
For a normal reading, use a quick controlled double tap. The taps should be close together, light enough to avoid driving the part unnecessarily, and delivered at the same location each time. On tops and backs, a repeatable voicing jig makes the information far more useful because the support condition stays the same from one reading to the next.
During brace carving, return the plate to the same jig, tap it in the same place, and watch how the dominant frequency moves as material is removed. The same approach can be used to vet raw material before a build by comparing boards under controlled dimensions and support conditions. The value is not in promising a better sounding guitar from a number. It is in removing variables so the results you consider your best work become easier to obtain again.
Charge Leave it on USB C between uses if that fits your bench.
Support Use the same jig, support points, and tap location.
Tap Use a quick, controlled double tap.
Adjust Carve, remeasure, and watch the dominant frequency move.
Record Keep the reading with the material or build record.
WHAT THE HAMMER DISPLAYS
Frequency and the closest musical note.
The display gives you the dominant frequency in hertz and the closest corresponding musical note at the same time. That makes the result useful whether you prefer to work numerically, by pitch reference, or by keeping both in the build record.
C3 +1.5Hz
132Hz
Closest noteC3, with the offset shown beside it.
Dominant frequency132 Hz, shown as the primary measurement.
ACOUSONIX FFT
Try the AcouSonix FFT.
Dominant Frequency
--- Hz
Overlay Manager
RAW PLATES BECOME MORE INFORMATIVE WHEN THE MODES ARE MEASURED SEPARATELY
Long, cross, and twist modes.
On raw plates, one frequency is not enough to describe how the material behaves. The long and cross modes are excited separately, and the twist mode appears as its own lower frequency response. The support method, dimensions, tap location, and technique need to remain consistent if those measurements are going to be compared with confidence.
LONG / O,2CROSS / 2,0TWIST / 1,1
A LONG HISTORY OF MAKING VIBRATION EASIER TO OBSERVE
The Frequency Hammer is another step in the evolution of useful voicing tools.
Instrument makers have always needed practical ways to understand how a structure responds. Long before electronic analyzers, builders flexed plates, tapped them, listened to pitch and decay, removed material, and listened again. The method was hands on and effective, but much of the information lived in the maker's ear and memory.
The tuning fork added a stable pitch reference to acoustic work. John Shore is credited with inventing it in 1711, and precision forks later became useful as both musical references and scientific frequency standards. Ernst Chladni made vibration patterns visible in the late eighteenth century by using particles on resonating plates to reveal nodal lines. That work eventually became part of the scientific language used to study plates and resonant structures.
In the twentieth century, Carleen Hutchins helped establish systematic modal testing as an important part of violin acoustics research. Guitar making followed its own path of structural refinement. Antonio de Torres became a defining figure in the development of the modern classical guitar, particularly through soundboard proportions and fan bracing that influenced generations of makers.
The Frequency Hammer belongs to that same practical lineage. It does not replace the builder's ear or judgment. It simply takes a familiar action, striking a resonant object, and uses FFT analysis to identify the dominant frequency immediately. That makes the observation easier to record, compare, and repeat throughout material selection, plate work, brace carving, and completed instrument analysis.
1711 · Tuning forkThe Whipple Museum documents John Shore's tuning fork and its later use as a musical pitch reference and precision scientific instrument.Whipple Museum source ↗
1787 · Chladni platesThe Smithsonian describes Chladni's method for revealing nodal patterns on vibrating plates and the later use of these figures in violin making and acoustics.Smithsonian source ↗
20th century · Modal plate researchCarleen Hutchins helped formalize free plate tuning and modal testing within modern violin acoustics research.Acoustics Today source ↗
Antonio de TorresThe Metropolitan Museum of Art describes Torres as a defining figure in the development of the concert guitar, including influential soundboard design and fan bracing.Metropolitan Museum source ↗
Modern handheld FFTIn Premier Guitar, Bryan Galloup describes FFT analysis as indispensable in tonewood and guitar work and explains how the AcouSonix Hammer brings that analysis into a handheld tool.Premier Guitar source ↗
BRYAN GALLOUP / ACOUSONIX PARTNER
Developed with Bryan Galloup and used in his working voicing process.
The Frequency Hammer is an AcouSonix product, and Bryan Galloup has been closely involved in its development as an AcouSonix partner. He approved the direction of the device, oversaw its development, and helped keep the measurement focused on the realities of instrument building. In his own work, Bryan uses the Hammer regularly while voicing guitars, including measurements of tops, backs, and completed instruments.
Bryan also takes the Hammer with him on European tonewood selection trips. A Galloup School account of the tool's development describes him using it in Italy and Switzerland to evaluate hundreds of tonewood samples more quickly than with older analysis setups. That field use matters because the same tool can move from a supplier's stack of wood to the voicing bench and then to the completed instrument without changing the basic measurement.
In a 2025 Premier Guitar column, Bryan wrote that he helped develop the handheld device and described how top, back, and air resonance readings can be used together to build a clearer tonal fingerprint of an instrument. His role with AcouSonix is practical as well as developmental: the Hammer is part of his own workflow, not simply a product he endorsed from a distance.
“This handheld device detects and displays the primary resonant frequencies of almost anything you tap.”
Read Bryan's article ↗
DevelopmentApproved the direction of the device and oversaw development as an AcouSonix partner.
Bench useUses the Hammer as part of his regular top, back, and instrument voicing workflow.
Tonewood selectionTakes the Hammer to Europe for on site evaluation of individual soundboards and tonewood sets.
Development and Europe field use ↗
A COMMON WAY TO DESCRIBE MATERIAL BEHAVIOR
A common language for material behavior.
One of the larger objectives behind AcouSonix is to make useful material information portable. Species and visual grading still matter, but repeatable measurements add another way to describe the behavior of an individual piece of wood and to communicate why it may be suitable for a particular use.
The point is not to replace selection by an experienced builder. The additional data gives that judgment a record that can be communicated, revisited, and compared with the results of later instruments.
Explore the AcouSonix Community →FOUNDERS EDITION
Designed specifically for tonewood and instrument work.
The Founders Edition was built around the practical needs of repeated instrument measurements. The body, striking tip, filtering, charging system, and OLED interface are all intended to keep the measurement fast enough to use throughout normal bench work.
- Filtering developed around tonewood and acoustic instrument response
- Integrated striking tip engineered to excite the surface
- Wooden hand-finished body and OLED readout
- USB C charging with solid overcharge protection, designed to remain on charge between uses
- No power button or setup sequence. Take it off the charger and begin tapping, or use it while plugged in
DIRECT PRODUCT SUPPORT
Questions can go directly to a co inventor.
Frequency Hammer owners have direct access to Cooper Wentz, co inventor of the device and a Galloup School instructor. Cooper has built hundreds of guitars alongside students, attended roughly fifty of Bryan Galloup's voicing lectures, tuned hundreds of guitar backs with students, and helped voice many guitar tops under Bryan's supervision. If you have a question about measurement technique, voicing jigs, material testing, brace carving, or how to interpret what the Hammer is showing you, reach out directly.
COOPER WENTZ
Co inventor / AcouSonix Frequency Hammer
Product use, measurement technique, voicing workflow, and shop application.
[email protected]FROM BUILDERS USING IT
What builders are saying.
★★★★★“I'm a retired Engineer from Texas Instruments, a split cane bamboo fly rod designer and builder and a guitar player for the past 63 years as well as an amateur acoustic instrument builder I have always been interested in the physics of acoustic instruments. I actually employ a process to frequency tune my bamboo fly rod tip sections on the rods I…”
★★★★★“The frequency hammer is indispensable. I use it on the top start to finish . I discovered a frequency my frequency analyzer did not pick up 35 Hz between the braces .”
★★★★★“This tool is a must-have if you care about resonance frequencies in your builds. It complements an FFT frequency response graph, enabling builds to be both better and more efficient. I use this hammer for four distinct purposes: 1) When examining raw tonewood, the hammer quickly reveals the long, cross and twist frequencies without guesswork. When coupled with the Acusonix software, these…”
★★★★★“The Accusonic Frequency Hammer has changed the way I voice guitars and evaluate wood. As a luthier, I have always relied heavily on experience, feel, and listening when selecting materials and voicing an instrument. The Frequency Hammer gives me a way to measure those observations and attach useful data to them. I can compare pieces of wood, document their resonant behavior, and…”
ACOUSONIX FREQUENCY HAMMER
Make your best results easier to repeat.
The Hammer is not intended to promise that a particular number will make a better sounding guitar. Its value is in controlling the measurement, reducing unknowns, and keeping a record of what happened. When a material choice or voicing approach produces the result you want, you have a clearer path back to it on the next instrument.
$450.00View / Purchase
FREQUENCY HAMMER FAQ
Practical answers before you purchase.
What does the AcouSonix Frequency Hammer measure?
It performs a frequency analysis after a strike and immediately displays the dominant frequency in hertz and the closest musical note.
What is included with the Frequency Hammer?
The product includes the handcrafted Frequency Hammer and a USB-C charger.
Does the Frequency Hammer replace a full FFT analyzer?
No. The Hammer is designed for a fast dominant-frequency reading at the bench. A full FFT shows the broader spectrum, multiple peaks, overlays, bandwidth, and additional detail. The two tools support different parts of the same measurement workflow.
Is it only for acoustic guitars?
No. It was developed around steel-string guitar work, but it can measure other resonant materials, instrument parts, violins, archtops, banjo heads, drums, and completed instruments.
Does it require a complicated setup?
No. Charge it by USB-C and begin tapping. There is no power button or measurement menu. Consistent support, tap location, and technique make comparisons more useful.
Where is the Frequency Hammer made?
Its components are handcrafted and designed within the Galloup School, with software developed under luthier Bryan Galloup’s approval and oversight.