The magic of semi-occluded vocal tract exercises

Are semi-occluded vocal tract exercises (SOVTs) new fad? Voice voodoo? Or a set of vocal exercises with scientific support that will prime your voice for singing and ensure vocal longevity? Chris and Steve delve into the world of SOVTs. 

To occlude. From the latin word “occludere” which means to shut, or close. That’s all very nice, but how on earth does it relate to singing? And more importantly, why are all these celebrity pop singers walking around singing through straws?

We are talking about the new wave of sexy vocal exercises that are referred to as SOVT exercises. If you’ve ever had any sort of vocal training, you’ve probably been using SOVTs for years. It’s only in the past 10 years that scientists have started to shed some light on why they work and how we can optimise them to benefit singers right across the land.

What are semi-occluded vocal tract exercises?

To give you some reference, we’re talking about anything that obstructs the airway when singing. Whether that comes from pursing the lips when blasting out your morning lip trill, or from a short piece of plastic (aka a straw), we have a whole host of SOVT exercises at our disposal which all have a differing effect on the vocal apparatus. Before we dig into this tool kit, let’s get a bit geeky and understand what in blue blazes is actually going on behind the occlusion.

The science behind SOVTs

You can take our word for it, or acclaimed voice scientist Dr Ingo Titze’s, but either way there is some crazy acoustic science involved with these exercises. In this instance, we are most concerned with the acoustic (think resonance) and aerodynamic (think airflow) “blockage” that is formed when we change the shape of the vocal tract.

Just in case you’re a bit late to the party, air is constantly flowing through the vocal tract when we are singing. In addition, acoustic energy is also constantly knocking about in the throat and mouth as a result of the vocal cords colliding as we chirp out our tune. Both of these forces are the fundamentals of sound production.

To understand what happens when we do a lip trill, for example, let’s spend some time thinking about a water hose. You know those wonderful family summers when you wanted to soak your little brother with the hose whilst watering the plants for your mum? Then you realised that you could force the water out quicker, thus making it sting a little bit, if you pressed on the end?

The force required for optimal skin sting is created by the water building up behind being the fingers and being forced through a smaller hole. In other words, water pressure in the hose is created from an occlusion.

In your mind, replace the hose with the vocal tract and you can start to visualise the build of acoustic and aerodynamic pressures within the throat and mouth when we pucker up for the lip trill.

What’s the point again?

Helpful pressure – unlike the hose, there are all sorts of other magical processes happening within the vocal tract at this time that can really assist us in creating an amazing sound. Firstly, this build up of oral pressure accumulating above the vocal cords works to counter the increasing air pressure below the vocal cords.

This means that the vocal cords have a helping hand in resisting the air from below, and don’t have to recruit unnecessary tension to handle the sudden gust! Higher oral pressure also increases (sorry in advance) intra-glottal pressure, which is the air pressure in the gap of the vocal cords.

This provides us with a comfy ‘air cushion’ that minimises the blows of each vocal fold vibration. Particularly through a straw, this allows for higher volume training with a massively reduced risk of injury.

The higher pressure also helps to un-press the top edges of the vocal cords, which can become squeezed from long periods of voice use.

Amazing acoustics 

Let’s all get excited about acoustics… please… just look interested ok? Occlusions trap vibrating air particles and keeps them to help the vocal folds to more easily sustain vibration over long phrases and movements. In essence, the vibration of the air particles makes air pressure quickly fluctuate, and it’s this that assists the vocal folds to open and close in every cycle.

Utter boffs like us will know this process as “inertance”. This makes occlusions a very efficient choice in a warm up routine! If you use a straw to do your stuff, then there’s the added benefit of a lengthening of your vocal tract.

The straw is essentially extending the distance between the vocal folds and the outside world. This provides more resonant frequencies (formants for the Vocal Nerd), and hence acoustic energy, to add to the melting pot and assist vibration. Nailed it.

The larynx and the vocal folds – (Oversimplification alert).

A semi-occlusion has a similar effect to stabilising the larynx through the passaggio, or break, and develops better transitioning between registers over time. The air pressures and acoustic energy also enhance our ability to achieve and keep a good tension in the vocal folds for range development. Uber-vocal geeks, we’re talking the tensions in the Thyroarytenoid muscle and the vocal ligament.

And the biscuits goes to…. Phonation Threshold Pressure (PTP)

Yes, that’s another amazingly hardcore bit of jargon. However, as voice teachers, we should be considering this in almost everything we do with our students. It’s simply the amount of breath pressure needed to set the vocal folds in vibration.

It’s different for different vocal qualities, for instance “belt” versus “head voice”. However, if this parameter is lowered in general as part of our training and warm up then we get a great sound for less cost to our voice. Hello, efficiency.

If this isn’t reduced then we can easily burn out faster and potentially cause damage. PTP is reduced through optimal vocal cord coordination and compression along with strong resonance; all of which you have read as SOVT benefits.

Our six top SOVT exercises

These nuggets of gold are listed in order of how slow they release air from the mouth. The slower, the more support and help. Faster is less. And all have their own place, which you’ll no doubt discover when trying them out. Let’s start with the slowest:

1. Straw exercise

The king of all SOVTs. Like any exercise, there really isn’t a one size fits all for optimal straw usage. A lot of this is about using, feeling and adapting. That said, there are some guidelines we can use. Choose your straw! The 3mm cocktail straw is a good starter’s choice. If one straw feels a little resistant or tight, use two, three or four of these at the same time.

First, though, we need to be okay with the random act of singing through a straw. Once that obstacle has been climbed, we can use a number of different approaches. The recommendation is to deliver your sound “forte”, or loud, during this exercise.

Remember that, especially to begin with, it may feel “clunky”, the high notes might be trickier than the low or vice versa and you may not actually enjoy the early stages of straw work. Sad face. We implore you to stick with it as, over time, you’ll start to feel a difference. You can watch this video from the good Dr Ingo Titze himself, to gain more insight into straw usage.

2. Bilabial occlusion – aka tight pursed lips

This is straw exercises, without the straw. In this exercise, we take the same approach as the straw but are using just the lips for resistance. It’s also different to a lip trill (next in the list) as during the bilabial occlusion we recruit more tension with lips in order to increase the occluded space.

3. The Lip Trill

Probably one of the most well-known vocal exercises of all time. The set-up is simple. Relax your lips and blow. If that doesn’t come easy, try mimicking the sound of a horse. If horses aren’t your thing, you can start by trying to “blow a raspberry” with your tongue and then replicating the sensation without the tongue immediately after.

Most people lift the tissue surrounding the mouth by placing their fingers on the jawline and gently pushing up. This reduces some of the lip resistance and can make the exercise easier to perform. We are reluctant to add the next sentence because those who can perform a lip trill, but don’t like to (normally because they think it’s weird) take it as an excuse to avoid the exercises all together.

The truth is, most people can perform a lip trill, but there is a small percentage of the population that can’t, due to the way they are made. If you have tried really, really, hard you may be one of these people… and in that case, we’ll let you off. But only if you’ve tried really, really, hard.

4. Voiced fricatives

Fairly straight forward these ones. Go to speak the letter ‘z’ (as in zoo), ‘j’ (as in the French word jouez), ‘v’ (as in very) or ‘th’ (as in that) and hold it. Hang around on that letter whilst performing the exercises we outline below. You’ll notice that each voiced fricative positions the vocal tract and articulators in different ways and resists air at slightly different rates. As a result you’ll probably find that one works better for you than others.

5. Tongue trill

If you’re native to Spain or any other Spanish speaking country, there’s a good chance you’ll be pretty good at rolling the old “r”. For those who aren’t, this may not come quite so easily. We have found that the tongue can often be over engaged with this exercise, so our advice is to proceed with caution.

6.  Nasal consonants

The least occluded of the SOVT family. There is a reason why singing teachers have been using sounds like ‘nay’ and ‘mum’ for years, and it isn’t just to make you feel silly. Go to pronounce an ’N’, ‘M’ or ‘NG’ and hold it. See if you can feel where the occlusion takes place… is it at the lips? Is it the tongue? Either way, these occlusions redirect our voice through the narrower passages of the nose and help us, even when humming. Momentary use of these, in combination with vowels, make for a superb transition from the crazier exercises outlined above to developing exercises and singing songs. Singing isn’t ever really as efficient and helpful as it is through an occlusion, but consonants in general occlude our vocal tract and help us maintain some of the greatness we have experienced when doing the weird stuff above.

Some suggested scales and exercises for SOVTs

1. Sirens – a firm favourite going through every microtone in the voice from bottom to top, stretching the vocal cord and developing smooth transition between the bottom and top of the voice.

2. Hills/accents – these are helpful for ‘un-squeezing’ tired vocal cords and waking up the breathing apparatus. See Dr Ingo Titze’s great video for a demonstration.

3. Sustains – take a tricky note anywhere in your range, and sing it with full intention through one of the occlusions above. Think ‘big-culminating-note-with-vibrato’ and see if you feel an improved ability to maintain the note and its volume whilst SOVT’d.

4. Melody – one of our favourites because you can really feel the difference afterwards, just belt out that wobbly nemesis lyric using an SOE several times. Then sing with confidence afterwards and see how it feels! You’re welcome.

The final word

We think Semi-occluded Vocal Tract exercises are brill. They have a solid of research behind them and have been helping singers clinically for years. Bringing these into your daily warm up routine, or even more than once per day, will help you to warm that uncooperative little monkey into a beautifully functional instrument in half the time. If your voice is ragged from last night’s gig they can also be very therapeutic and help to iron out bad muscle patterns without adding insult to injury.

Either way, when singing after dabbling with the straw or a bilabial occlusion you’ll no doubt feel your PTP reduce… umm… or it just gets easier. 

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Chris Johnson and Steve Giles are both experienced vocal coaches working in Southampton and London. They are with the Vocology In Practice teacher network and specialise in training clients in advanced vocal technique, style and improvisation. They are co-founders and presenters of the popular iTunes singer’s interest podcast The Naked Vocalist. As well as coaching and podcasting they are also in-demand performers and manage their own successful soul acts.