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Machine and Human Testing


How We Test

In addition to human playing tests, one way we study the air column of trumpet and its different elements is to use “extra-human” testing to remove the variability of the musician. The accuracy and repeatability of a skilled trumpet player is on the order of plus or minus 5 musical cents (each “cent” is 1/100th of a semitone) which makes it difficult to ensure consistency between player tests, even with the same musician.

We use both human play tests and machine testing to insure accuracy and playability in our designs

One tool that we use, the salpingometer, is accurate and repeatable to within plus or minus 1 cent (approximately 5 times more accurate than the best human ears). This apparatus maintains a constant pressure input to the trumpet (or element of the trumpet) over a series of single frequencies, to permit accurate measurement of the driving point acoustic impedance of the acoustic element. This yields an accurate plot of acoustic impedance versus frequency. We choose to perform measurements at individual frequencies instead of injecting broad spectrum frequencies in order to maximize the accuracy of our measurements. This apparatus provides consistency in test results, allowing for comparison of different configurations. This level of accuracy also provides the ability to perform multiple adjustments to an air column that may be desired. The ability to account for different amounts of lip penetration is a critical feature of the apparatus. Player tests correlate well with the extra-human testing results.

Original Cardwell Salpingometer

Original Cardwell Salpingometer

Bill Cardwell established his salpingometer in the early 1970’s and consulted with Gary Bast on the development of his next generation apparatus which he has used since 2000. The Bast salpingometer was designed so it does not require drilling a hole in the mouthpiece to receive the acoustic resistor which is used to excite the trumpet system to be tested.

In musical terms:

Put simply, the above method gives us the means to measure the accuracy of intonation and the width of the slots, which we can then use to improve designs. Since our goal is to provide an improved musical experience for the player and the listener, we always use human player tests to confirm that any adjustments or new designs yield the desired improvement.


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  • Salava, Tomas “Acoustical Impedance Measurement using Constant Volume Velocity”, JASA 67 No 5, May 1980 pages 1831-1833.


Current Bast Salpingometer

Current Bast Salpingometer