There are a number of models and choices when deciding to purchase a system to measure noise. In some cases multiple microphone and preamplifier models will do the job for the same application. The following information will help you choose the system that will work best for the application. For additional information please download the PCB Microphone Handbook.

Microphones Field Types
There are three common application fields for precision condenser microphones. The first and most common is the free-field type. The free-field microphone is most accurate when measuring sound pressure levels that radiate from a single direction and source, which is pointed directly (0º incidence angle) at the microphone diaphragm, and operated in an area that minimizes sound reflections. A free-field microphone is designed to measure the sound pressure at the diaphragm, as it would appear if the microphone were not present. When a microphone is placed in a sound field, diffraction effects will alter the sound pressure when the frequency is high enough so that the wavelengths are similar in size to the dimension of the microphone. The effect is accounted for in the design of the microphone and the resulting correction factors are applied to the actuator response during calibration. These microphones work best in open areas, where there is no hard or reflective surfaces. Anechoic chambers, or larger open areas are ideal for these Free Field microphones.