Development of a Weatherproof Windscreen for a Microphone Array Development of a Weatherproof Windscreen for a Microphone Array

by Hill, Jeffrey R

Microphone windscreens are typically used to reduce the noise associated with wind flowing over a microphone diaphragm by reducing the velocity of the airflow. While most windscreens are effective at reducing this noise, they do not protect the microphone from many natural elements, such as moisture, sand, and other small particles. The focus of this research was to design a windscreen that protects an array of five microphones located around a 4.5-inch diameter cylinder from these natural elements. The design goals were to have a wind noise attenuation of at least 8 dB, an insertion loss of less than 1 dB from 5-1000 Hz, and a phase shift error of less than 3% over the same range.

Computer simulations and experimental testing were used to select two basic designs. Four experimental tests consisting of wind noise attenuation, sand entrapment, insertion loss, and phase change measurements were used to optimize the geometry of these designs. The wind noise attenuation was tested by spinning the microphone array on a long boom and by setting the array in front of a fan. Sand was blown at the windscreen in order to test how well the windscreen protects the microphone array from small particles in the velocity stream. The insertion loss of the windscreen was tested by comparing an incoming signal traveling through the windscreen to the same signal without the windscreen. Finally, the phase shift between microphones was measured using a single frequency and comparing the microphone measurements with and without the windscreen. These four tests were performed on two designs.

The first design consists of two foam filled concentric cones set around the microphone array. The second design consists of tubes that project outward from each microphone diaphragm, and then curve downwards.

Both final windscreen designs meet the desired requirements. They both reduce wind noise attenuation by approximately 9 dB in a 13 mph wind and over 16 dB in a 20 mph wind. They also have negligible insertion loss, have a phase shift error of less than 3%, and are very efficient at blocking particles from entering the windscreen.