Microphone Testing

Applications of SoundCheck for Microphone Testing Include: Electret Condensers Pro Audio Microphones Wireless Microphone Systems USB Microphones MEMS microphones
Industry Standard Microphone Tests Frequency response Sensitivity Phase Self-noise and signal-to-noise IM Distortion Simulated free-field response Directional characteristics (polar plot) Impulse response Max SPL

Features and Benefits of SoundCheck for Microphone Testing

Frequency Response
SoundCheck features a variety of test signals and analysis methods for measuring the frequency response of a microphone. The source speaker can be calibrated such that any stimulus signal is equalized to remove the influence of the speaker’s magnitude and phase response.  SoundCheck’s stepped sine Stweep is the perfect choice for use in an anechoic chamber, test box, or for proximity tests. It can easily be optimized for the desired trade-off between accuracy and speed. For an extremely fast production test, use the Multitone stimulus, which plays a series of discrete frequencies simultaneously. You can even use an equalized speech or music WAV file as a stimulus and analyze the microphone’s response with the Transfer Function module.  

Simulated Free-Field Response
Not everyone who wants to measure a microphone’s free field response has an anechoic chamber at their disposal. Typically the problem with measuring free field response in a non-anechoic room is the influence of room reflections on the measurement. With SoundCheck’s Time Selective Response algorithm these reflections can be time-windowed out, and the resulting frequency response is anechoic and accurate. A log sine sweep is used as the stimulus.The algorithm calculates the impulse response, and a user-defined time window is placed around it, eliminating the influence of room reflections. 

 Directional Characteristics
Measuring directionality is a key part of any microphone testing. With SoundCheck, a microphone can be tested at multiple angles, and the data can be displayed on a single graph. This angular data can also be used to calculate the Directivity Index curve versus frequency, as well as generate polar plots for discrete frequencies. SoundCheck can also automate the entire process of directivity measurements by directly communicating with a turntable via GPIB or RS-232.    

Distortion
Most traditional audio analyzers are only capable of measuring one type of distortion, THD (total harmonic distortion). This measurement does not work for microphones, as the source speaker will almost always exhibit higher THD than the microphone under test. There is, however, another method.  SoundCheck can measure the distortion of a microphone using an intermodulation distortion technique and two separate sound sources. One source is used to produce a fixed tone and the other is used to produce a sine sweep. In this way, the harmonic distortion of the sources is excluded from the measurement, and only the selected intermodulation components from the microphone are measured.

Typical Microphone Test System Configuration

A typical microphone test system consists of the SoundCheck Basic System that includes stepped-sine sweep (Stweep™) excitation, frequency/phase response, and a calibrated high-end sound card. Optional SoundWare modules include the Real Time Analyzer and polar plotting. Turnkey systems including computer, reference microphones, test chambers, and audio amplifiers are also available.