Acoustics Study: Innovative Spray Design Makes Turbines Especially Quiet

Posted on May 6, 2014


The noise level of dental turbines stems not only from the operating and drilling noises, but from the spray as well. New Sirona instruments with a four-nozzle spray were the best in a comparison of ten turbines from various manufacturers.

Noise-induced hearing loss has long been one of the most common occupational diseases. Many dentists complain about the high noise level during treatment from the high-pitched whir of their turbines that make it difficult to concentrate and can cause stress or tinnitus. Over time, hearing loss can develop. Advacoustics, an engineering office in Berlin, studied the noise levels from turbines of various manufacturers and how the new turbine generation from Sirona compares.

New four-nozzle spray effectively reduces the noise level

The acousticians compared turbines of various manufacturers with respect to acoustic pressure, loudness, and sharpness. It was clear that the noise is not caused only by operating and drilling sounds, but also from the spray used for cooling. "The measurement of the noise level can reflect the actual working conditions during treatment only if the turbines are tested using spray," says Dr. André Jakob, Managing Director of advacoustics.

Most turbines were significantly louder in the test when they were operated with spray, sometimes up to 10 dB (A), which is equivalent to doubling the noise level. The smallest differences in acoustic pressure were found with the two Sirona turbines T1 Control S and T2 Boost S, which were only 2.2 or 0.2 dB (A) louder when using spray than without. The reason: Sirona introduced a new generation of turbines in 2013 with an innovative four-nozzle spray. Thanks to this innovation, the Sirona turbines were quieter than the other models tested when using spray. In the oral cavity simulation, the acoustic pressure was 60.1 or 61.1 dB (A). This is equivalent to the noise level during the normal routine in a dental office. The competitors’ products reached levels between 63.5 and 73.8 dB (A), some of them exceeding the noise levels caused by cars at a distance of ten meters. "The test results confirm our development work. After equipping our turbines with low-vibration ball bearings and rotors, we reduced the noise level even more with the innovative four-nozzle spray for the benefit of dentists and patients," said Frank Peichl, Instruments Product Manager at Sirona.

Lower sharpness of resonance is more pleasant

Because the spray emits high-frequency tones, reducing noise in the turbines also affects the sharpness of resonance, which is perceived to be unpleasant at high levels. When using spray, both Sirona turbines were measured at 2.8 acum, the unit for sharpness, in the simulation on the oral cavity. The measurements of the competitor turbines were from 3.0 to 3.7 acum.

More power from the new generation of turbines from Sirona

In addition to the greatly reduced noise level, the Sirona turbines in T1 Premium class and T2 Comfort class also have perceptibly more power and better control. With a pressure of 3 bar, they have an output of up to 23 W. While the sleeves of the T1 turbines are made completely of long-lasting titanium, the T2 turbines are coated with titanium. This material is both non-slip and easy to clean. The turbines are sterilizable and thermodesinfectable. Sirona offers the turbines in three different versions ‒ as a highspeed Boost version, a mini head turbine with a diameter of only 10.2 millimeters, and the CONTROL version with a patented speed control for smoother operation.

"SoundCheck" app illustrates the low noise level

To make it clear how quiet the Sirona turbines are, the company developed a SoundCheck app. The aim of the game is to arrange drilling noises and sounds in nature according to their noise level. Participants in the game can win Sennheiser HD 600 stereo headphones.

The "Sirona SoundCheck" is available in the app store at:

Facebook users can access the app at

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