Groundbreaking technology for surface microphone

Anti-Corrosion Methods and Materials

ISSN: 0003-5599

Article publication date: 1 June 2004



(2004), "Groundbreaking technology for surface microphone", Anti-Corrosion Methods and Materials, Vol. 51 No. 3.



Emerald Group Publishing Limited

Copyright © 2004, Emerald Group Publishing Limited

Groundbreaking technology for surface microphone

Groundbreaking technology for surface microphone

Keywords: Aircraft industry, Microphones, Corrosion resistance

The Type 4948 surface microphone is the first in a new family of microphones from Bruel and Kjaer using groundbreaking technology.

Designed in close co-operation with a leading aircraft manufacturer, the Type 4948 is an aerodynamic, easy to use, robust and stable measurement microphone for use on airplane surfaces during in-flight testing, as well as in wind-tunnel testing and other similar applications.

It eliminates the many drawbacks of flush mounting experienced with traditional microphones, as it is not only flat and small measuring just 2.55 mm in height with built-in preamplifier but also supports TEDS and is based on new technology.

The compact design makes drilling holes in the test object a thing of the past, but its measurement performance, stability and uniformity are equivalent to those of the traditional, well known Bruel and Kjaer microphones and amplifiers.

Surface microphone Type 4948 has a built-in DeltaTron preamplifier for connection to CCLD inputs. The microphone sensitivity is adjusted to allow measurements at high levels without clipping. Offering high mounting flexibility with a diaphragm, which is flush. The microphone housing and the metallic parts of the diaphragm- backplate arrangement are all titanium, ensuring uniquely high resistance to corrosion.

Despite its small dimensions, the Type 4948 is corrosion-resistant and can withstand de-icing detergent and harsh environments (for example, normal aeroplane cruising altitudes of 30,000 ft, mach 0.8, turbulence and hailstorms).

In addition, the microphone's pressure equalisation vent is placed next to the diaphragm on the front of the microphone, a very important prerequisite as static pressure can vary rapidly with the position in the applications for which the microphone is designed. Type 4948 is a prepolarised pressure microphone and its features include: a dynamic range from 55 to 160 dB; frequency range of 5 Hz to 20 kHz; temperature range: −55-+100°C; sensitivity of 1.4 mV/Pa; support for TEDS standard IEEE P1451.4; flush mounting; and is optimised for pressure-field measurements.