How to Make a Breath Pressure Gauge

Ever wonder just how much air pressure you are using to play a note? Curious about the differences in pressure needed for high pitches versus low pitches, loud versus soft notes?

A breath-pressure gauge can be made fairly easily. The parts required are as follows:

• a sphygmomanometer
• several feet of 1/4" aquarium tubing
• a small, thin plastic straw typically used as a coffee stirrer
• some all-purpose glue, such as Duco-Cement.

What is a sphygmomanometer? It is a blood pressure gauge, the sort normally attached to a cuff with a hand-pump. I was able to buy an older model from a medical supply store for under $20.

The tube which connects the gauge to the cuff should be easy to detach. It can be replaced with a length of clear aquarium tubing. I recommend bringing the gauge to an Aquarium store to ensure the tubing you buy fits on the gauge's nipple. There, you can buy the tubing by the foot instead of purchasing a whole roll online. A few feet to a yard should be sufficient. For my gauge's nipple, 1/4" tubing was a perfectly secure fit.

This size tubing is a bit too large to comfortably hold in the mouth while playing the oboe. At first I tried attaching a ring around the end, so that it would be less prone to slipping out while I was blowing. The white band used can still be seen in the photo. Even with this added security, the tube still disrupted my embouchure.

Then, while stirring my morning coffee at the local cafe (where we are lucky to have an owner that imports beans from his home country of Yemen!), inspiration struck in the form of the thin plastic straw coffee stirrer.

You can coat a half inch or so of the outside of the straw with a good all-purpose glue that adheres to plastic, and carefully insert the glue-covered portion into the aquarium tube. Then, to help ensure the seal, I would add glue all the way around the outside end of the tube. Give this a few hours to dry, and the seal should be strong enough to allow you to play without air leaks.

To use, I tuck the coffee stirrer into the far corner of my mouth while either crowing the reed or playing.

A blood pressure gauge typically shows measurements in mmHg (milligrams Hg). To convert to Pascals, another unit of measurement, you can use the following formula:

 1 mmHg = 133.3 Pascal

One atmosphere is roughly 100 kPa (100,000 Pascals) .

You might compare your measurements with those of the oboists shown in a chart presented in The Physics of Musical Instruments, Second Edition, (c) 1998, by Fletcher & Rossing. I've substituted single numbers (medians) for the ranges given in the book.

NOTE	VOLUME	kPa	mmHg
C4	p	4	30
C4	f	6	45
A5	p	5	37.5
A5	f	10	75

Only the bottom third or so of the gauge will be relevant. A trumpet player might use as much force as 15 kPa (112.5 mmHg) for the highest, loudest notes, but pressures above this are quite difficult to achieve. At those levels, the pressure could match or exceed the systolic blood pressure of the neck's arteries. If you blew hard enough to constrict blood flow, most likely dizziness or fainting would result!