Intensity Microphone Kit 1/2″ GRAS 40AK Class 1

Introduction

• The 40AK is an IEC 61043-complian ½” externally polarized sound-intensity microphone pair. Read about the prepolarized equivalent 40GK.
• The microphones in the kit are two 40AI microphones – two phase-matched free-field measurement microphones with extremely well-controlled phase characteristics for use in sound-intensity probes. This microphone pair has a free-field frequency response that complies with IEC 61043 1993 Class 1 and IEC 60651 Type 1 in the range from 20 Hz to 10 kHz.
• The 40AK kit also includes solid spacers for 12 mm, 25 mm, 50 mm, and 100 mm intensity-probe configurations, as well as adapters for the 26AA ¼” LEMO preamplifier set. The 40AK is a part of the GRAS 50AI LEMO Sound Intensity Probe.
• 40AK is individually factory-calibrated and delivered with a calibration chart, stating its specific open-circuit sensitivity and pressure frequency response.

Typical applications and use

• The 40AI is designed for sound-intensity and sound-power measurements, as well as sound-source localization, which is why it is included in the 50AI probe in the 40AK kit. Each 40AI microphone pair is phase matched according to the phase specifications for a Class 1 Sound Intensity Probe in accordance with international IEC 61043, Electroacoustics – Instruments for the Measurement of Sound Intensity – Measurements with Pairs of Pressure Sensing Microphones, 1993.
• The quality of a sound intensity probe microphone is its ability to measure the real part of a complex sound intensity in highly reactive sound fields as well as in sound fields exposed to high levels of background noise. This ability depends largely on the phase responses of the microphone pair. The individual phase matching of each 40AI ensures that any differences in phase responses are extremely small.
• The 40AI is also used for ranking of sound sources. When mounted in the 50AI sound-intensity probe, the microphones can pinpoint the area generating the most noise, which may then require additional measurements, depending on the measurement procedures and processes used. The sound-intensity microphones reveal the weak and strong points when identifying noise sources. Sound-source ranking is useful as long as the background noise doesn’t exceed the noise source.

Compatibility

• The 40AK includes straight and right-angled adapters for ¼” LEMO preamplifiers, which require an input module that supports this technology with a 7-pin LEMO connector.
• In the 50AI Sound-Intensity Probe, the 40AK pair is combined with the 26AA ¼” LEMO preamplifier set.