Interpreting stroboscopy – what do you see?


Jeremy Fisher in the voice clinic during a stroboscopy examination

Interpreting stroboscopy – what you see isn’t always the truth. How do you translate what you see as a singing teacher or vocal coach?

A World Voice Day special

Singing and speaking are the manifestations of sound – as a listener, we don’t have to see what’s happening to understand the sounds. After all, it’s possible to have a conversation with your eyes closed. So why are singers, singing teachers and vocal coaches getting so hot under the collar about interpreting stroboscopy and mapping it onto vocal physiology and vocal technique?

I believe some of the heated debate stems from the interpretation of visual cues – interpretations that can quickly become enshrined as a belief system. Putting those visual cues into a broader context can often give the viewer a better, more accurate explanation of what’s going on.

Let’s get practical

Watch this stroboscopy video of me sliding through two octaves (opens in a new tab here.)

Vocal fold vibration

Watch the video again, this time focusing on the vocal folds themselves in the centre of the video. The vocal folds are vibrating pretty consistently. Notice in this stroboscopic view that they seem to vibrate at the same speed throughout the two octaves. In addition, the larynx seems to fall and rise as the pitch gets lower and higher respectively. You could interpret that as “the vocal folds do not change for different pitches”, and “pitch changes are caused only by the height of the larynx”.

What is stroboscopy?

To interpret this correctly, you need a lot of background information. Let’s start with stroboscopy itself. How does it work? Mehta, Deliyski and Hillman in their excellent article “Why laryngeal stroboscopy really works” say:

“Modern clinical videostroboscopy systems automatically estimate the subject’s vocal fundamental frequency from a neck sensor (usually a contact microphone or electroglottograph) as a basis for synchronizing the video capture rate to the flash rate of the strobe light or shutter speed of the camera to record stroboscopic images of vocal fold vibration.”

Notice I’m wearing a black band around my neck – this Electroglottograph band is measuring the speed of closure of my vocal folds and feeding that information in real time to the camera chip in my mouth. The camera then adjusts its strobe light to almost match my speed of vocal fold closure.

Why almost?

Stroboscopy and cycles per second

Well, if the camera matched my speed exactly, my vocal folds would look like they were standing still. So the camera is programmed to adjust to perhaps 2 cycles per second slower, and take a shot periodically. So if I am singing A220 (A below middle C), the camera might be snapping away at 218. This means that each time the camera snaps, my vocal folds have completed a cycle and are fractionally further on in the next cycle. (Incidentally, if the camera snapped 2 cycles per second faster, my vocal folds would appear to vibrate backwards…)

The result of this is that you see my vocal folds apparently vibrating at exactly the same speed throughout the two-octave slide. In reality, the camera is matching its speed to my pitch speed throughout.

Making sense?

Now watch the video again. Notice as I slide to the top note, the space inside my throat gets narrower? The back and side walls of my throat move in, almost covering the arytenoids and leaving very little space.

Interpreting “space”

The first interpretation might be that there is something wrong, based on your current understanding of vocal technique. For example, “the throat should always be wide”, “everything should be relaxed”, and “the pitch changes should happen without anything else moving”. We even had one comment on this video when it was released, along the lines of: “there’s something wrong with the top note, it’s not as rich as it should be”. This is where theoretical beliefs and reality tend to collide.

Moving from the lowest note to the highest note, I am making my vocal folds quadruple their speed of vibration. I’m also staying in a modal vibration and not popping into falsetto. So at the very least I am tensing/stretching my vocal folds substantially to enable them to vibrate at four times the speed of the lowest note. It may be balanced, but it ain’t relaxed!

I’m using the walls of the throat and the raising of the larynx as a supporting mechanism to stabilise my larynx. If I have something vibrating that fast inside my throat (and the larynx is a suspended mechanism), it’s going to start moving around, and the last thing I want when I’m on a full-out top note is to have a shaky larynx.

More context

Also, here’s where you need more context. I’m a bass. That top note is as high as I go in modal voice. I even remember filming this, starting the lowest note and thinking half-way up: “can I actually reach the top note?” Oh, and if you check the beginning of the video again, you’ll see that

a. the camera is in a long metal tube sitting on the very back of my tongue (gag reflex, anyone?), and
b. the surgeon is holding my tongue, pulling it out as far as it will comfortably go, and
c. I’m stretching my neck forwards and “out of line” because it’s the best way to get the clearest picture.

So is it actually bad to have “a tight throat” like this? No, because I’m not tight where it matters, just above the vocal folds.

Where space in your throat matters

Run the video once more and notice the false vocal folds, just to either side of the true (white) vocal folds. Notice that they don’t come in at all during the slide. My false vocal folds stay opened and out of the way, even on my highest note, even under those (tricky) circumstances. My true vocal folds vibrate healthily and in balance for each pitch, and my false vocal folds stay out of the way so I am not constricting. That open-ness at vocal fold level is what really matters.

Now you have more context for the video – bass voice (ie large, heavy vocal folds), vibrating at the highest modal note, an open throat where it’s needed so remaining healthy, and a camera that matches the speed of the vocal folds to give a consistent movement image.

The point of this article? Before you decide what’s happening, understand the context. At Vocal Process, context is everything!



If you want to check your understanding of how voices work, or just try a few things out, book a 1-1 session online or in person with Jeremy or Gillyanne here