Microphone Testing
- 1. APPLICATION NOTE Microphone Testing System Overview SoundCheckTM is an easily configurable, Windows- based system for efficient and comprehensive testing of microphones. Applications include: • High-speed Production Testing • Incoming Inspection • Research and Development • Capsules • Systems • Test in an ordinary room without an anechoic chamber SoundCheck uses a variety of readily available hardware and software including anechoic test boxes, measurement microphones, and databases to measure and report all parameters related to microphone test and measurement. SoundCheck’s measurement results can satisfy in-house performance standards as well as AES and other standards. In addition, SoundCheck can control external devices, such as turntables, using RS-232, USB, or IEEE interfaces. and real speech. One-button calibration, a large number of measured data points and advanced Production Testing mathematical algorithms ensure unparalleled SoundCheck is fast for production line measure- accuracy for measurements in both the time and ments, performing comprehensive tests in a the frequency domain. matter of seconds. Test sequences can be pre- programmed for simple pass/fail analysis or Features and Benefits detailed results that can be exported to other One-button Calibration programs such as Excel for additional processing. The entire measurement chain, including refer- SoundCheck can be easily integrated into existing ence microphone, audio amplifiers, and sound test programs that use ActiveX controls or National source, is easily calibrated by simply clicking on Instruments LabVIEW®. One-button operation, one button in SoundCheck. An external acoustic barcode control and assignable security levels calibrator is used to calibrate the reference give you total control over your production testing. R&D Applications SoundCheck also offers unrivalled flexibility for Industry Standard Tests R&D applications - with SoundCheck, you are no longer constrained by the limitations of proprietary • Frequency response hardware-based systems for testing microphones • Phase and capsules. SoundCheck is easily configurable, • Distortion making it perfect for a laboratory environment • Simulated free-field response where a large number of different tests need to be • Directional characteristics carried out. Tests can be selected from a standard • Impulse response library and customized test sequences can be • Self-noise and signal-to-noise programmed and modified via a simple point-and- • Max SPL click programming interface. Any WAV file can be • Polar plots used as the input stimuli, including sine, noise 450 Harrison Ave • Suite 307 • Boston • MA 02118 • Tel: (617) 556-4104 • Fax: (617) 556-4104 • email: info@listeninc.com www.listeninc.com
- 2. Microphone Testing Typical System Configuration SoundCheck™ SoundConnect Microphone Mic Power PASSED Testing Supply Sound Card L Input Phantom Power (optional) Sound Card Output to Amp Input Microphone Under Test Power Amplifier Output to Speaker 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 com- puter, reference microphones, test chambers, and audio amplifiers are also available. microphone, which then can be used to calibrate the Distortion sound source. The magnitude and phase of the Measure the distortion of a microphone using an source is equalized for a flat response. The position intermodulation distortion technique using two of the test microphone, relative to the sound source, separate sound sources. One source is used to can be measured acoustically thereby enabling easy produce a fixed tone and the other is used to alignment to the reference position. produce a sine sweep. In this way, the harmonic distortion of the sources is excluded from the Application-specific Modules measurement. Only the selected intermodulation SoundCheck application-specific modules enable components from the microphone are measured. you to create functionality specific to your measurement needs and budget. Modules include Limits the Signal Generator, Voltmeter, Oscilloscope, Limits can easily be created from a measured Spectrum (FFT), and Real Time Analyzer. For real- response by offsetting the curve in frequency, time “hands-on” investigation of microphones, the amplitude, or time. Signal Generator can play a sine wave, a noise signal or any Windows WAV file at a calibrated output level. The response of the microphone can then be analyzed in the time and frequency domain using the Oscilloscope, FFT or Real Time Analyzer. Simulated Free-Field Response Free-field amplitude, phase, and impulse response of any test microphone can be measured using the substitution method. Directional Characteristics You can measure the directional characteristics at any angle manually or automatically using a turntable such as the B&K 9640 IEEE controlled turn- table system. Off-axis responses at any Microphone Specification Sheet number of selected frequencies or over a range of frequencies can be displayed on a polar plot. www.listeninc.com