NVH Technical Articles

A Tutorial on Active Noise Reduction - (by the technical staff of LightSPEED Technologies) This is a five-part series on Active Noise Reduction in General Aviation. It came about because hundreds and hundreds of you have been asking good questions about ANR technology and its advantages in airplanes. This series is intended to provide G.A. pilots with a fairly technical and thorough understanding of this technology and the important criteria that will affect performance and long term satisfaction While not exhaustive, you should "graduate" with a clear picture of the role active cancellation can have on your flying safety, comfort and overall enjoyment.

Noise Control in Buildings - (from Building Science Insight) This publication is one of a series of reports produced by the Institute for Research in Construction, National Research Council of Canada. It covers the following topics: Basics of Noise Control (R.L. Quirouette and A.C.C. Warnock), Sound in Rooms (J.S. Bradley), Sound Transmission through Building Components (J.D. Quirt), and Acoustics in Practice (A.C.C. Warnock).

Application Notes

Materials Properties - (BO0211-11.pdf, August 1997, 4pp, PDF File: 213KB) Measurement of Sound Reduction Index with a Single/Dual Channel Real-time Analyzers . Sound reduction index is one parameter used to determine the efficiency of noise barriers.

Reverberation Time - (BO0228-11.pdf, August 1997, 4pp, PDF File: 368KB) Measurement of Reverberation Time Using a Simple Sound Level Meter. Reverberation measurements are used to determine the properties of a room where noise absorption materials may be used such as theaters, concert halls, classrooms, etc.

Improved Method for Complex Modulus Estimation - (BO0427-11, September 1996, 8pp, PDF File: 552KB) In industrial products, vibration and the noise it creates is often a major parameter to be taken into account. It is therefore usually very important to measure the material properties i.e. stiffness and damping, that determine how vibrations are generated, transmitted and damped. This application note describes a method which will allow the standard non-resonant method for the determination of complex modulus to be used at higher frequencies than otherwise possible.

Gearbox Analysis using Cepstrum Analysis and Comb Liftering - (BO0440-11, 4pp, PDF File: 195KB) Cepstrum analysis has many applications: for example echo detection and removal, or speech analysis, but the most important one in industry is related to machine diagnostics, where its ability to detect periodicities in the spectrum is taken advantage of.