How We Test - Windscreens UNDER CONSTRUCTION
In addition to having our products independently tested for acoustic transparency and effectiveness at a major university, they have 1) also been independently tested by one of our re-branding partners, and 2) undergone extensive product testing in our own facilities in Colorado and New Jersey. Over the years, we have developed considerable wind noise creation and reduction expertise related to our cycling products - which we leverage for our windscreens. We have tested close to 100 different faux fur / pile lengths, thicknesses, fiber compositions... at various wind speeds, laminar vs. variable turbulent flow, etc.
During our testing, we quickly discovered that absurdly long fur was not required for significant wind noise reduction. While it may, to some, imply effectiveness, it really isn't necessary for smaller microphones. We should also mention that longer / thinner fur tends to mat (losing effectiveness) and requires combing. Our products are as simple to use as foam covers - but much more effective.
Wind is by its nature turbulent and variable. It may have a nominal direction but it will have component eddies that can appear from any compass point. To make a laboratory machine that can accurately emulate this truly chaotic performance is not easy. A few have been built (1) but they suffer from some defects, not the least of which being that they are very large and very expensive. Nonetheless microphone windshields cannot be tested and measured without some form of wind so Rycote felt that there might be an advantage in evolving a technique that did not rely on such equipment but still gave accurate and repeatable results. The technique that was devised uses real wind and obtains measurements by comparing two microphones in real-time. One microphone acts as a “naked” control while the other is “clothed” in the wind noise reduction device.
The use of real wind is likely to be particularly useful when evaluating the performance of a device that might be sensitive to angle of incidence such as those that streamline the rear of a microphone. It is also probable that this technique will give an accurate indication of what a microphone suffers in actual use.
Testing in the Lab
Most wind tunnels are designed for testing of aerodynamic effects like drag, and are very noisy. Aeroacoustic testing requires extensive noise suppression, and these quiet wind tunnels are rare, specialized, and very expensive. Cat-Ears has built three quiet open jet wind tunnels. With careful attention to sound and vibration damping, they are remarkably quiet for the volume of air moved. We have constructed "test heads" (Custom Acoustic Test Simulators - CATS) that are equipped with realistic silicon ears and simulated ear canals. Miniature condenser microphones are placed in the ear canals - at the location of the ear drum. This is critical for correct real ear WNR measurements.
Because wind noise varies significantly by speed, we capture wind speed data during our test runs and extract exact cycling speed information from our Garmin 520. The digital anemometer and Garmin data is matched to the recorded sound files to help ensure that our road testing conclusions are as accurate as possible.
And, of course, periodic equipment testing and re-calibration is essential for accuracy.
We use probe microphones for accurate real in-ear measurements (REM) - similar to those used by audiologists. The tip of the probe tube is placed approximately 5 millimeters from the eardrum. This allows us to measure wind noise more accurately. We have read about people measuring wind noise by placing a microphone at the center of the rider’s outer ear. Anyone who has held a microphone in the wind or even just breathed at one will know that they can be susceptible to small variations in air pressure, causing false wind noise signals known as 'pseudo-sound'.
However, instrumented road testing is not without its challenges. Wind direction and wind turbulence levels can change rapidly. Exact orientation of the cyclist's head (yaw / pitch) is difficult to control. Because of these issues, we augment our road testing with aeroacoustic testing performed under carefully controlled laboratory conditions.
Our quiet open jet wind tunnels allow us to measure sound pressure levels while carefully controlling wind speed, direction, and head orientation. One limitation of our tunnels is that we can't make them free of acoustic reflections (anechoic). Another limitation is that we can't see precisely what is happening with the airflow.
Unmatched Performance Testing Capabilities = Unmatched Product Performance