How a note works
PHY-01How does a single tone field produce a pitch?#
beginner
Short answer. A tone field is a small area of the shell that has been hammered into a shallow dished shape, thinned and put under carefully controlled internal stress so that it behaves like a semi-independent plate. Strike it and it flexes at its own natural frequencies, and the lowest and strongest of those is the pitch you hear.Nothing is attached and nothing is tensioned in the way a string or a drum head is. The tuner is working with three variables in the metal itself: the area of the field, its thickness, and its curvature together with the residual stress locked into it. Larger and thinner lowers the pitch; more curvature and more prestress raises it. Every hammer blow moves some combination of the three, which is why tuning a handpan is a slow iterative process rather than a single adjustment.
When you strike the field, you deform it briefly. The steel’s elasticity pushes it back, it overshoots, and it oscillates. Because it is a two dimensional plate rather than a one dimensional string, it can oscillate in many different spatial patterns, called modes. Each mode has its own frequency and its own map of where the steel moves most and where it barely moves at all.
The untuned steel around the field is what makes this work. It is thicker, stiffer and differently curved, so it presents a large impedance mismatch at the edge of the field. Vibration reaching it is largely reflected back into the field rather than escaping across the shell. Without that boundary you would have one enormous ringing dome, not nine separate notes.
The dimple or small dome at the centre of the field plays into this too. It stiffens the middle of the plate, which changes the shapes the field can vibrate in and helps suppress some high, harsh modes. Makers differ on exactly how they use it.
Finally, the field is not radiating in free air. It is the skin of a closed cavity with a port, and that cavity pushes back. See PHY-09.
See also: PHY-02
PHY-02What are the three tuned partials?#
beginner
Short answer. On a properly built handpan each tone field is tuned so that three of its vibration modes line up: the fundamental, an octave above the fundamental, and a compound fifth, meaning a fifth above that octave. If the fundamental is D3, the other two are D4 and A4.This is the defining trick of the instrument and it comes straight from the Trinidadian steelpan tradition that PANArt came out of. Wikipedia’s description of the Hang puts it plainly: each tone field contains a fundamental tone, an overtone tuned to an octave above that fundamental, and an additional overtone a perfect fifth above that octave. PANArt’s own writing uses the same three: the fundamental note, its octave, and its fifth above that octave.
In interval terms the three partials sit at frequency ratios of roughly 1 : 2 : 3. That matters, because 1 : 2 : 3 is the beginning of the natural harmonic series, the same series a vibrating string produces. A plate does not naturally do this. Left alone, a flat plate’s modes fall at ratios that are not simple whole numbers at all, which is why an unshaped sheet of steel sounds like a crash rather than a note. The tuner’s job is to force three of those inharmonic plate modes into a harmonic relationship by shaping and stressing the metal.
Because the three partials line up with the harmonic series, your ear fuses them into a single pitch with a rich timbre rather than hearing three separate tones. That fusion is what makes a handpan note read as a note.
Higher modes exist and are not tuned to anything in particular. PANArt described up to a dozen further natural harmonics distributed across the higher frequency regions, and these contribute the shimmer and complexity above the tuned three. A tuner will suppress the ugliest of them but will not try to place them precisely.
Variations exist. Some makers and some instruments use a fourth rather than a fifth as the third partial, or aim at fundamental plus two octaves. These are deliberate design choices, not errors, but the octave plus compound fifth arrangement is overwhelmingly the standard.
PHY-03What happens when the partials drift?#
intermediate
Short answer. The note stops sounding like a note. Instead of one fused pitch you hear a wobble, a beating or a metallic clang, and the field loses sustain because the modes are no longer reinforcing each other. Small drift is common and tolerable; large drift is what people mean when they say an instrument has gone out of tune.Alignment is what makes three modes read as one sound. When the octave partial sits, say, fifteen cents sharp of a true octave, it no longer coincides with the second harmonic your ear expects from the fundamental. The two beat against each other, producing a slow pulsing that you hear as instability rather than as two pitches. Drift the fifth as well and the fusion breaks down further and the note takes on a clangy, gong like quality.
Sustain suffers too. When modes are harmonically related they share energy coherently; when they are not, the energy exchange becomes messy and the note dies faster and less smoothly.
Drift has several causes, and they behave differently:
- Playing too hard, especially with mallets or sticks, gradually deforms the tone field and moves the partials. This is the most common cause and it is permanent until retuned.
- Impact damage from a drop or a knock can move a note dramatically in one event.
- Repeated temperature extremes stress the steel and the seam over time. Ordinary daily temperature variation is not a concern.
- Poor original tuning. An instrument rushed through its final tuning has stresses that have not been properly relieved, and it will settle and drift much sooner than a patiently built one.
Note that not all wobble is drift. Crossover, the wave interference in the air cavity, produces a wobble on specific notes that is a property of the shell geometry and cannot be tuned out. Saraz measured typically 20 to 50 cents of wobble on B flat 4 in the sustain of their 21 inch instruments, and stated plainly that this happens no matter how well the note is tuned. Before concluding an instrument is drifting, check whether the affected note sits in that band for its shell size.
Handpans can be retuned, by the original maker or by a specialist. It is skilled work and not every instrument is worth it.
See also: PHY-13, TRB section
PHY-04Why does a handpan note sound harp-like or bell-like?#
beginner
Short answer. Harp-like because the tuned partials sit in a harmonic 1 : 2 : 3 relationship, exactly as a plucked string’s do. Bell-like because the untuned higher modes above them are inharmonic, exactly as a bell’s are. A handpan note is genuinely both at once, which is most of why it is so distinctive.Break the spectrum into two layers and it becomes clear.
The bottom layer is the three tuned partials. Fundamental, octave, compound fifth. That is the opening of the harmonic series, and it is what a string does naturally. Your auditory system is superbly good at recognising that pattern and collapsing it into a single fused pitch with a warm, singing character. This is the harp, or the plucked string, in the sound.
The top layer is everything above those three. Plate modes that have not been forced into any particular relationship, spread across the higher frequencies. That is what bells, gongs and cymbals produce, and it gives the shimmer, the metallic sparkle, and the slight sense of a cloud of sound hovering above the pitch.
Two more ingredients thicken it further. The Helmholtz resonance of the cavity, typically somewhere around C2 to G2 and measured at about 85 Hz on the Hang, sits underneath everything and adds a low breath. And every strike also excites the neighbouring tone fields, which answer at their own pitches. PANArt catalogued seven distinct contributors to the Hang’s sound: contact noise from the hand, the cluster response of the whole resonator, hammered vibration modes, coupling between harmonically related fields, the overtones of each field, the indirect stimulation of neighbouring fields, and the Helmholtz resonance of the cavity.
The proportions between these layers are what you are actually judging when you compare instruments. A very bright instrument has a strong inharmonic upper layer, which reads as metallic or, unkindly, tinny. A very dark one has it suppressed, which reads as warm but can sound dull. Good makers place it deliberately.
The attack transient matters too. The first few milliseconds, before the modes settle, contain a burst of broadband noise from the hand meeting the steel. That is a large part of why fingers, fingertips and thumbs all sound different on the same note.
See also: PHY-07
PHY-05Why do neighbouring notes ring when I strike only one?#
intermediate
Short answer. Two paths. Mechanically, vibration leaks through the shared steel of the shell into the surrounding fields. Acoustically, the sound in the air and in the cavity drives them. Fields whose frequencies are harmonically related to what you played respond most strongly, which is why the effect usually sounds pleasant rather than muddy.This is sympathetic resonance, the same phenomenon that makes an undamped piano ring when you sing into it. A tone field is a tuned oscillator, and any oscillator will pick up energy from a driving force close to one of its own frequencies.
The mechanical path is the shell itself. The interstitial steel is a good boundary but not a perfect one, so a small fraction of the struck field’s energy travels outward as bending waves and arrives at other fields. PANArt named this explicitly as one of their seven sound sources, distinguishing coupling, meaning energy transfer between harmonically related fields, from neighbours, meaning the indirect mechanical stimulation of adjacent fields.
The acoustic path runs through the enclosed air. The struck field radiates inward as well as outward, the cavity air carries that energy across the instrument, and it arrives at the underside of every other field. This path is why the effect is stronger with the port unobstructed and why it changes when you sit the instrument on your lap.
The zigzag note layout is designed partly around this. By putting scale neighbours on opposite sides of the circle, makers ensure that the notes which are physically adjacent, and therefore couple most strongly through the steel, tend to be a third, fourth or fifth apart. Those relationships are consonant, so the sympathetic ringing reinforces the harmony rather than clouding it. See ANA-03.
There is a limit to how much you want. Too much coupling and individual notes lose definition, sustain shortens because energy is escaping the struck field faster, and fast playing turns into a wash. This is one of the practical costs of squeezing extra notes onto a shell, and one of the things experienced players listen for when evaluating an instrument: strike one note firmly, and ask whether the answer from the rest of the instrument is a halo or a mess.
See also: PHY-06
PHY-06What is sustain and what governs it?#
intermediate
Short answer. Sustain is how long a note remains audible after the strike, and it is governed by how quickly the vibrating field loses energy. Losses come from three places: internal friction in the steel, radiation into the air, and leakage into the rest of the instrument. Material, sheet thickness, tuning quality and build all feed into it.A struck tone field holds a fixed budget of energy and spends it. Sustain is simply how slowly it spends.
Internal damping. Every flex cycle turns a little of the energy into heat inside the metal. This is a material property and it is why steel choice matters. PANArt listed low energy absorption and high restoring force among their explicit design targets for the nitrided sheet. Stainless instruments are widely reported to sustain longer than nitrided ones, and long controlled sustain is the main selling point of proprietary stainless such as Ember.
Radiation. Energy that becomes sound has left the field, and that is the useful loss. A field coupled efficiently to the air is loud and short; one coupled inefficiently is quiet and long. There is a real trade off here, and it is not one makers can escape.
Leakage. Energy travelling out of the field into the surrounding steel and into neighbouring fields is gone from the note you played. Well isolated fields with generous interstitial steel around them ring longer than crowded ones, which is one of the hidden costs of high note count layouts.
Two more factors:
- Thickness and stiffness. Thicker, stiffer fields store more energy relative to what they lose per cycle, so they generally ring longer.
- Tuning quality. Well aligned partials sustain more smoothly. Misaligned ones beat against each other, and the note both dies faster and dies unevenly. See PHY-03.
Sustain is not straightforwardly a virtue. Very long sustain means notes overlap, which is glorious for slow ambient playing and problematic for fast rhythmic playing. It also gives you more time to hear crossover wobble on affected notes. Plenty of experienced players deliberately choose shorter sustaining nitrided instruments for exactly this reason.
Typical figures vary far too much between instruments, notes and materials for a single number to mean anything. Judge it by ear, on the instrument, playing what you actually play.
PHY-07Why does hitting harder change the timbre and not just the volume?#
advanced
Short answer. Because the tone field is a curved, prestressed shell rather than a simple linear spring. Hit it harder and it deforms further, its effective stiffness changes with amplitude, and energy spills into higher modes that a soft strike never excites. Louder and brighter arrive together, and past a point the pitch itself bends.A linear oscillator scales cleanly: twice the input gives twice the output at the same frequencies. Real tone fields are not linear. Two things break the linearity.
Geometric nonlinearity. A shallow dished shell resists small deflections one way and large deflections differently, because deflecting it far enough starts to stretch the material in the plane of the sheet rather than merely bending it. Stretching is much stiffer than bending. The result is that effective stiffness rises with amplitude, so a very hard strike momentarily sharpens the note before it settles back as the amplitude decays. That downward pitch glide during the first moments of a loud note is audible on most instruments if you listen for it.
Mode coupling. Once nonlinearity is in play, modes stop being independent. Energy pumped into the fundamental can transfer into higher modes, including the untuned inharmonic ones. That is why a hard strike sounds not just louder but brighter, edgier, more metallic and more bell like, while a soft strike sounds pure and flute like.
There is a third, more mundane contributor: the attack transient. The contact between hand and steel is broadband noise, and its spectrum depends on how fast and how rigidly the hand arrives. A relaxed fingertip and a stiff knuckle at the same volume produce measurably different transients.
Practically, this is the whole basis of expressive handpan playing. Dynamics on a handpan are timbral, not merely loud and quiet. Ghost notes played at very low amplitude sound warm and rounded because the upper modes are barely excited; accents sound bright and cutting because they are. Most of what distinguishes an experienced player from a beginner is control over this dimension.
It is also why hitting hard damages instruments. Deform a field far enough, often enough, and the deformation stops being elastic and starts being permanent, which moves the partials. See PHY-03.
PHY-08Why does a handpan note decay so slowly compared with a drum?#
advanced
Short answer. A drum head is light, heavily damped by the air it drives and by the shell it is stretched over, and its modes are inharmonic, so its energy dumps into the room fast. A handpan tone field is stiff steel with very low internal friction, coupled inefficiently to the air, and its main modes are harmonically aligned, so it hoards energy and releases it slowly.Compare the two systems directly.
Mass and stiffness. A drum head is a thin membrane with no bending stiffness of its own, held up entirely by tension. Its restoring force comes from that tension, and it is light enough to be strongly loaded by the air it pushes. A steel tone field a millimetre thick has real bending stiffness and real mass. It is far less affected by the air it is driving.
Radiation efficiency. This is the biggest factor. A drum head is a large, light piston that couples extremely well to the air, which is exactly why drums are loud and why they stop quickly. Good coupling means fast energy transfer, and fast energy transfer means short decay. A handpan tone field is smaller, heavier and stiffer, and it radiates far less efficiently. That inefficiency is why it is quieter than a drum and why it rings for seconds rather than a fraction of a second.
Internal damping. Skin, plastic and the rope or lug hardware of a drum all convert vibration to heat readily. Nitrided or stainless steel is an unusually low loss material, and makers select and treat it specifically to keep those losses low.
Harmonic alignment. Because the three tuned partials sit at ratios near 1 : 2 : 3, they do not beat destructively against each other. Inharmonic partials, which dominate most drums, interfere and smear the sound into a short, noisy burst.
Termination. A drum head is clamped at its rim to a shell that absorbs energy. A tone field is bounded by a stiffness mismatch that reflects energy back into it rather than absorbing it.
There is one more contribution unique to this instrument: the cavity. Energy that leaves the field is not immediately lost to the room. Some of it circulates in the enclosed air and in the other tone fields, and comes back. That recirculation extends the audible tail even after the struck field itself has quietened.
See also: PHY-12, REL section