To help engineers meet increasingly strict aerospace environmental noise regulations, Brüel & Kjær created a lightweight, robust Portable Impedance Meter System - Type 9737.

Regulations put pressure on aerospace engineers to improve liner attenuation - and this drives the need for improved acoustic impedances in jet aircraft acoustic liners. Acoustic Liners are vital to ensure aircraft are quiet and must satisfy many other requirements too, such as withstanding extreme weather and fitting restricted spaces.

Fully bonded panels within aircraft must be assessed for their true, effective acoustic behaviour in their final condition. Brüel & Kjær's Impedance Meter System provides aerospace engineers with a user-friendly system, suitable for carrying out research and production quality control impedance measurements, up to 150 dB SPL on engine nacelle liners.

The system allows key acoustic parameters, such as impedance spectra vs. OASPL and acoustic resistance versus acoustic velocity, to be extracted in-situ. An automated pass/fail routine allows non-acoustic specialists to quickly carry out production quality control measurements.

The system is based on the two-microphone, transfer function test method, which means measurements take only a fraction of the time required by traditional, standing-wave ratio systems.

The Portable Impedance Meter system lends itself well to the measurement of acoustic properties of aircraft interiors and trim materials.