How we think about the noise a phone system should make.
By Cory Schruth · Washougal, WA
The first contact most people have with a phone system is its sound. The ring. The little beep when you press a number. The faint click before someone picks up. The voice that says hello. These get into your bones over decades. You can’t see a phone system, mostly, but you hear it every day.
Most of those sounds were designed before any of us were born. The North American dial tone is a chord of 350 and 440 Hz, established by AT&T in the 1930s. The DTMF tones, the matrix that plays when you press a number on a keypad, were invented at Bell Labs in 1963 and have not been altered since. These were not arbitrary choices. They were engineered to be distinguishable from human speech, easy to detect across noisy copper wire, and hard to reproduce by accident.
We are not going to redesign any of those. They work. They are part of the substrate.
What we are going to do is design everything else. Below are the principles we’re working from. Then Arrival, the primary ring and the sound we think of as the philosophical center of the whole thing. Then the rest of the ring family, the small moments inside the interface, an atlas of identity sounds, and the practical signals built to be heard when beauty isn’t the point. Press the buttons. Tell me what you think.
01
Our root is 432 Hz, not 440.
A deliberate departure from concert pitch. The standard tuning of A=440 Hz was internationally codified in 1955 and has been the reference for almost every commercial sound made since. We use A=432 Hz instead, which is roughly thirty-two cents flatter: a small enough shift that you don’t consciously notice it, large enough that the difference between two systems is measurable.
Why 432? There’s a long tradition of people claiming spiritual properties for it, most of which we are not interested in. The reason we use it is simpler: it sounds warmer. The same harmonic intervals played on a 432 root land a little softer in the ear, a little less brittle, a little more organic. Every interval, ratio, and harmonic on this page is calculated from this root. The 5th above 432 is 648. The octave below is 216. The pentatonic ladder we use for the Arrival ring is 432 → 486 → 540 → 648 → 864.
You’re not supposed to notice this. It’s part of what makes everything else feel the way it does.
02
Every tone carries texture.
A pure sine wave is sterile. It sounds like a hearing test. Real-world tones (bells, voices, wood blocks, kalimbas) all carry small amounts of broadband noise alongside the pitch. That noise is what makes them feel like objects in the world rather than signals in a graph.
Almost every sound on this page has what we call a grain layer: bandpass-filtered noise, mixed in at very low gain, decaying quickly. Enough to feel tactile. Not enough to be audible as noise. Felt, not heard. If we took it out, everything would sound a little colder and you wouldn’t be able to say exactly why.
03
Direction is the meaning.
Ascending means arrival, connection, opening, success. Descending means departure, close, silence, undo. The direction is the meaning, and we use it consistently across every category of sound we make.
Once you internalize this rule, you can tell what happened in a NocTel surface without looking at the screen. A toggle going on ascends; a toggle going off descends. A call connecting rises; a call ending falls. A confirmation lifts; an error drops. It is not subtle, and it is not arbitrary. It is the closest thing we have to a grammar.
Call Connected432 → 648 Hz · ascending two-tone
The moment someone picks up. The 5th above the root.
Call Ended648 → 432 Hz · descending two-tone
The same two notes in reverse. Same materials. Opposite meaning.
04
Brand Territory sounds are portraits, not utilities.
Some of the sounds in our palette aren’t trying to indicate that something happened. They’re trying to indicate who made the thing that’s making sound. These are identity sounds, drawn from the actual world NocTel comes from. The Columbia River Gorge. Buried fiber. The moment a panic button reaches dispatch. The seal on an encrypted file. The terrain we’re literally on.
They’re fixed-frequency, not adjustable. They’re portraits. You’ll see a whole atlas of them further down. We don’t claim every customer will notice them or recognize them as a set. We make them anyway, because they are part of how NocTel sounds when you listen closely.
NocTel Brand SoundThe signature
The whole identity in a single gesture: the sound NocTel makes when it introduces itself. Every portrait in the atlas below is a facet of this one.
05
The center of all of this is the primary ring, a sound we call Arrival.
If you ever want to know what NocTel sounds like in one sound, this is the one. We’ll say more about it just below.
The philosophical center
Arrival.
Five notes, climbing. A pentatonic figure rooted at 432, the same low, warm note everything else is tuned from, rising and opening out, each note ringing a little longer than the one before it, with a breath of grain under the first so it sounds like it’s coming from somewhere real.
It’s the primary ring. The sound a NocTel phone makes when someone is trying to reach you.
Rising means one thing in this system, and it always means the same thing: arrival. Someone is here. The line is opening. Whatever comes next (a voice, a question, a problem, good news) begins the instant this sound does.
Ascending is arrival. This is the half-second before hello.
That’s the whole company, in five notes. Phones, paging, panic buttons, signage, file delivery: every one of them exists to produce this single moment: one person reaching another, and the other person knowing it. Most of what we build is plumbing for that event. This is the event itself.
Ringtones
The rest of the family.
Arrival is the primary ring. These are the other ways to ring, every one tuned to the same 432 root, so the whole set sounds related. Press to hear.
Marimba
Warm mallet · 432 pentatonic
A soft mallet lilt through the 432 pentatonic (432, 648, 540, 864), built additively with a strong fourth-harmonic partial, the overtone that gives real marimba bars their woody ring. Quick attack, gentle decay. A familiar ring, still tuned to the brand’s own note.
Bluebird
Playful · rising chirps
Three quick two-note chirps, each pair leaping upward and each landing higher than the last (648→864, then 720→972, then 864→1080), with a bright tick on every one. Birdlike, but kept in tune.
Sunbeam
Ascending arpeggio · shimmer
A fast major arpeggio climbing the 432 series (432, 540, 648, 864), capped by two shimmer notes an octave higher, over a breath of airy noise. Sunlight breaking, in half a second.
Arabesque
Debussy · wave arpeggio
A pentatonic figure that flows up to 972 and falls back to 432 in one legato breath, the rise and fall of a single phrase after Debussy’s Arabesque. Soft grain throughout. One wave, there and gone.
Pulse
216 Hz · meditative
A six-note melody rooted at 216 Hz, one octave below our standard 432, moving through the harmonic series and back home. Long sustained notes, slow organic pitch settles. More felt than heard on good speakers. The candidate for customers who would rather their phone breathe at them than chime.
In the interface
The small moments.
The sounds you hear inside the portal and on a call: brief, low, and out of the way until you need them.
Voicemail
Descending · three notes
Three tones stepping down from the fifth to the root (648, 540, 432), each held a little longer than the one before, over a low breath of grain. Descending always means one thing here: something set down, left for later. A message, waiting.
Menu Open
Airy rise
Two quiet tones lifting from just under the root, 346 up to 432, carried on a wash of high, airy grain. Brief and upward. Rising means opening. The sound of something making room.
Submit / Save
Committed · forward
A short noise transient, then two tones stepping up and out (389 to 583), firm and fast. Upward, but with weight behind it. A decision sent, not just made.
Brand Territory
An atlas of identity sounds.
Derived from the actual landscape NocTel comes from. These are not utility sounds. They are portraits we’re still drawing.
Signal Bloom
Noise → clean tone
Half a second of pink-shaped noise centered around 432 Hz, dissolving into a clean ascending tone that lands on the root. The NocTel promise made audible: chaos resolved into clarity.
Resonant Stone
Inharmonic partials
A singing-bowl character. The fundamental at 432 plus two inharmonic partials at unusual ratios (2.756× and 5.404×, the ratios real bronze bowls actually produce). Long organic decay. What weight sounds like.
Intro Sting
5 layered harmonics
Five harmonics of 432 layered with overlapping attacks, each lasting longer than the next. An open tail rather than a close. The sound a brand would make if it were entering a room and didn’t want to interrupt the conversation.
Practical
When beauty isn’t the point.
Sounds that have to be heard.
A warm, calm ring is the right default. It is the wrong tool in a machine shop.
Some of these sounds exist to be beautiful and, most of the time, nearly invisible. Others exist to cut through a room full of forklifts, or thirty kids. We built both and kept them apart, because the design rules are opposite.
For a noisy room, the move is to go high and to pulse. The ear is most sensitive between two and four kilohertz, and a loud room has the least competing energy up there. A steady tone gets masked and then ignored; a pulsing one keeps re-catching the ear. So the high-visibility rings sit in that band and repeat, in a short ladder of rising intensity, so an installer can match the sound to the room instead of guessing.
Hard of hearing is the opposite problem, and it’s easy to get backwards. Hearing loss usually takes the high frequencies first, so a piercing high alarm points straight at the range a listener has already lost. The research goes the other way: a low, harmonically rich tone around 520 Hz alerts people with hearing loss far better, and it’s written into accessibility codes. Our accessible alarm sits low on purpose. The accessible ringtone does the same, in a friendlier form.
Emergencies don’t get a brand voice. When something is wrong, recognition beats personality, so we used the signals people already know without being taught: the three-pulse rhythm that means evacuate, the two-tone ambulance call, a real bell with the inharmonic ring of struck metal. They’re built to be unmistakable, not pretty, which for a safety signal is the only thing that counts.
And for anyone who just wants a phone to sound like a phone, there’s a small set of familiar rings (a bell, a ringback, a trill) pulled quietly back toward 432, so even the ordinary options belong to the same family.
A note from Cory
I have been thinking about this for twenty years.
The reference I always come back to is the Cisco Call Manager ringtone from the early 2000s, that distinctive double-pulse that meant the call coming in is on a corporate line. You heard it from across an office and you knew, without seeing the phone, which kind of phone was ringing.
I want NocTel to have that. A sound that, when you hear it, locates you. Not branding in the heavy sense. Just a small audible signature that tells you whose system you’re hearing. Most platforms have given up on this. We’re not in a hurry, but we’re trying not to.
What you’ve heard on this page is the current draft of a system that’s been in pieces in my head for a long time. Some of these sounds will survive to the production palette. Some won’t. Arrival will. That one I’m sure about.
What’s still being figured out.
Whether the ring family needs another voice in a register lower than Pulse. The hold-music question (do we want hold music? do we want hold silence?). The conference-bridge entry and exit sounds: we’re prototyping a version where each participant joining gets a different note ascending the scale, so you can tell from sound alone how many people are now on the line. The small flourish that plays when an Action Editor flow saves cleanly.
There’s a constraint we work inside the whole time: nothing we make can overlap the DTMF tone matrix. If a tone falls on one of the sixteen frequency pairs that operate keypad signaling, such as the 697/1209 pair (the “1” digit) or the 770/1336 pair (the “2”), some routing equipment in the wild will interpret it as a button press and try to act on it. We avoid those frequencies entirely. The 941 Hz row (the bottom of the keypad: *, 0, #) is retired from our palette permanently.
We’ll keep posting drafts here as we work on them. If you have opinions about the ring family, the number is on the home page.