How We Test
Our original products were tested on the road and with a quiet open jet wind generator. Our new products are rigorously tested on the road, trail, and in our custom labs. We employ a variety of specialized testing techniques. Each technique has its pros and cons. Together, they represent a level of rigor that no competitor can match.
Testing on the Road
Road testing allows us to evaluate performance in actual use situations. We do this in two ways. The first is riding with the product at one ear and without at the other ear. We then record impressions. The second is to instrument cyclists with special in-canal microphones, record wind noise at known speeds (by extracting Garmin data), and then calculate the sound pressure level reductions. Our experience shows that while our acoustic measurements cannot predict exactly how much wind noise reduction a cyclist will experience, they provide reasonable expectations.
We use professional probe microphones for accurate real ear measurements (REM) - similar to those used by audiologists. The tip of the probe tube is placed approximately 5 millimeters from the eardrum. This is the most accurate way to measure wind noise. 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 blown on one knows that they are susceptible to small variations in air pressure (and self-generated noise), causing inaccurate measurements.
However, instrumented road testing is not without its challenges. Wind direction and wind turbulence levels can change rapidly. Exact orientation of a cyclist's head (yaw / pitch) can be difficult to control. Because of these issues, we augment our road / trail testing with aeroacoustic testing performed under controlled laboratory conditions.
Testing in the Wind Tunnel
Most wind tunnels are designed for evaluating aerodynamic effects like drag and are noisy. Aeroacoustic testing requires extensive noise suppression, and these quiet wind tunnels are rare, specialized, and expensive. Cat-Ears designed and built two 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.
We test using multiple helmet brands (Bell, Giro, Bontrager, Rudy, etc.) and retail price points (<$50 to ~$250). We also test with different cycling eyewear. Helmets and eyewear can impact the amount of wind noise.
Three Custom Acoustic Test Simulators (CATS) and Two Quiet Open Jet Wind Tunnels allow us to perform extremely controlled testing variations (variable speed, yaw, pitch) in both Colorado and New Jersey.
Road to Wind Tunnel Coherence
Understanding the difference between road and laboratory testing is important. Accordingly, we perform CATS vs. real head comparisons in the wind tunnel. Identifying differences helps us make better measurement comparisons.
Wind Tunnel - Smoke Visualization
Over the past several years, we have developed effective 15 - 35 mph wind tunnel smoke visualization capabilities.
Hydrodynamic Flume - Flow Visualization
Since wind noise is created by airflow, we need to understand the aerodynamics of air flowing around a cyclist's head and the impact on the airflow when using Cat-Ears. Visualizing airflow, especially when looking for very localized turbulence, is difficult. However, air and water are both fluids, and their behaviors are essentially the same at low speeds. Thus it is possible to do 'aerodynamic testing' using water and observe those flows in great detail.
We designed and built a water tunnel known as a hydrodynamic flume - to meet our unique test requirements. The test chamber is large enough to hold a 'slice' from one of our simulated heads. We can pump water through it to reach an airspeed equivalent of 15 MPH. We inject fluorescein dye into the flow and illuminate it with LED and laser ultra-violet lamps. We then capture high-resolution videos and photographs, allowing us to see differences in turbulent flow patterns as we design changes to our products.
Multi-faceted testing helps us develop the most effective products.