Why Your High Notes Crack: The Science of Phonatory Threshold Pressure

Ever wondered why some notes feel effortless while others crack or don’t come out at all? The answer lies in phonatory threshold pressure (PTP)—the minimum air pressure needed to start and sustain sound. In this episode of The Voice Science Podcast, we break down what PTP is, how it’s calculated, and why it matters for singers.

Discover how PTP affects vocal efficiency, vocal fatigue, and even vocal warm-ups. We’ll also debunk common myths about breath pressure, including the idea that “more air is always better” and that pushing harder is the key to volume. Instead, learn smarter, science-backed techniques for singing powerfully without strain.

👉 Try the simple vocal exercise in this episode to explore how little pressure you actually need to sing clearly. Plus, get a sneak peek into next week’s deep dive into ring and twang—two powerful tools for enhancing your voice without overworking your breath.

🔬Phonation Threshold Pressure Formula:
Pth = 0.14+.06(Fo/|Fo)^2 kPa

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📌 Links & References:
Elliot, N., Sundberg, J., Gramming, P., 1995. What happens during vocal warm-up? Journal of Voice 9, 37–44. https://doi.org/10.1016/S0892-1997(05)80221-8

Titze, I.R., 2000. Principles of Voice Production, 2nd printing. ed. National Center for Voice and Speech, Iowa City, IA.

Episode Transcript

Josh (00:04):
Have you ever wondered why some notes seem harder to sing
than others or why your voicecracks under pressure?
The answer might lie insomething called phonatory
threshold pressure or PTP.
Welcome to the Voice SciencePodcast, where we dive into the
science behind all thingssinging and teaching.
Here you'll learn how the voiceworks and discover practical

(00:26):
tips to train it moreefficiently.
I'm Josh, the founder ofVoicescienceorg.
I've been educating singers andteachers for the last 13 years.
In today's episode, we'retaking a deep dive into the
science of phonatory thresholdpressure, a fascinating concept
that explains the minimum airpressure needed to make and

(00:47):
sustain sound.
We'll break down what it means,why it matters and how it
connects to vocal efficiency,vocal warm-ups and vocal fatigue
.
Let's get started.
So what is phonatory thresholdpressure and why should we care?

(01:08):
I first ran across the termphonatory threshold pressure, or
PTP, during my master's whilereading Ingo Tietze's book
Principles of Voice Production.
I read the second printing from2000, but it was originally
published in 1994.

(01:29):
Phonatory threshold pressure isthe minimum pressure required to
start and sustain phonation inkilopascal KPA.
PTP is an important concept forunderstanding vocal efficiency,
something all of us want.
Most people aren't veryfamiliar with Pascal or
kilopascal, so for a little morecontext, 1 psi or 1 pound per
square inch is equivalent to6.89 kilopascal, a small amount

(01:56):
compared to the 45 to 80 psitypically found in residential
water pressure or the 30 to 42psi in car tires water pressure,
or the 30 to 42 PSI in cartires.
But even for the respiratorysystem one kPa is a tiny amount
of pressure.
According to a 1993 study byFiz, trumpet players can

(02:21):
generate 23 kPa of exhalatoryforce.
So we know that PTP is theamount of subglottal air
pressure required to start andsustain phonation.
But how is it calculated?
To calculate PTP we use aformula that considers the note
you're singing and your averagespeaking pitch.

(02:42):
For example, if I want to singA440, my PTP is about 0.9
kilopascal, but for a woman witha higher speaking pitch, it's
almost half of that, around 0.46kilopascal.
This shows how individualfactors, like your natural
speaking pitch, influence thepressure your voice needs to

(03:05):
sing.
Okay, so from this we know thatthe minimum amount of
subglottal air pressure to startand sustain a note changes by
individual and that we can makesome general assumptions based
on that person's averagespeaking fundamental frequency.
If you're curious about yourPTP.
I'll include the formula in theepisode notes.

(03:29):
Now that we know this about PTP,why should singers know
anything about it?
Have you ever tried to sing anote and nothing came out or it
sounded creaky?
That's likely because yoursubglottal pressure wasn't high
enough.
Now, on the flip side, have youever cracked on a high note?

(03:50):
Yeah, yeah, me too.
That's even more common.
In this case you probably hadtoo much pressure and your vocal
folds couldn't keep up, so theyshifted to a partially open
position to release the excesspressure.
A great exercise is to try andfind how little pressure it

(04:10):
takes to sing a note.
Pick any note, a note in aneasier pitch range, for you will
be easier.
But don't let that stop youfrom being bold.
Sing that pitch on the vowel ofyour choosing and try and sing
it where it kind of just creaksout.
Increase the pressure just alittle until that note

(04:31):
stabilizes.
It will be quiet.
Now let's take a moment toaddress some misconceptions
about breath pressure.
The most popular one is moreair pressure is better.
More subglottal air pressurecan lead to increased loudness
and in fact it is even requiredto sing louder.

(04:54):
But while more pressure canhelp you sing louder, it often
leads to tension, vocal fatigueand even injury if overdone, and
with microphones being used inmost genres, the focus should be
less on sheer volume and moreon the quality of your sound and

(05:15):
your vocal health.
While that myth is about moreair pressure, the second myth is
just about sheer volume of air.
Pushing more air is the onlyway to sing louder.
This one seems actually ratherintuitive, since we know that
increased subglottal pressurecan make you louder, but it

(05:38):
turns out this is only one way.
To a pretty reasonable extent,you can increase the intensity
of your singing by increasingbrightness through the use of
ring or twang, which increasesthe intensity of harmonics in
the 2-5 kHz range.
Instead of relying on bruteforce, think of twang as an

(06:02):
efficient amplifier for yourvoice.
It lets you sing with morepower and brightness without
pushing harder.
We'll dive more into ring andtwang in a future episode, so
stay tuned.
A quick mental exercise if youare not driving a car or
operating heavy machinery, Iwant you to think about a time

(06:24):
you were told to use more airwhile singing.
Think about how your voice felt.
Was it easier, was it harder?
It could have been either one.
The point is that more air isnot.
Today, we explored thefascinating concept of phonatory
threshold pressure, or PTP, theminimum amount of air pressure

(06:49):
needed to start and sustainsound.
We broke down what PTP is, howit's calculated and why it
varies between individuals basedon factors like speaking pitch.
On factors like speaking pitch,we also discussed how
understanding PTP can helpsingers avoid vocal fatigue,
improve efficiency andtroubleshoot issues like

(07:10):
cracking or failing to start anote.
We debunked commonmisconceptions about breath
pressure, like the idea thatmore pressure is always better
or that pushing more air is theonly way to sing louder.
Instead, we touched onalternatives like using
resonance and twang to amplifyyour voice efficiently without

(07:33):
overworking your breath support.
And, finally, I shared apractical exercise to help you
experiment with your own PTP anddiscover just how little
pressure it takes to sing astable, clear note.
Thanks for tuning into the VoiceScience Podcast.
If you found today's episodehelpful, share it with a friend,

(07:54):
teacher or fellow singer whomight enjoy it.
Don't forget to subscribe soyou never miss an episode.
Next time we'll dive deeperinto the science of ring and
twang, two powerful tools toenhance your singing with less
effort.
Until then, keep experimenting,keep learning and keep singing,
and check out voicescience.

(08:14):
org for more articles, researchand tips.
We'll see you next time.