Engineering Acoustics

7Noise and Vibration Transducers, Signal Processing, Analysis, and Measurements

7.1 Introduction

In the measurement of noise and vibration fields, it is necessary to sense the sound or vibration disturbance with a transducer. The transducer converts some physical property of the sound and vibration field into an electrical signal. This signal is then amplified, attenuated, or transformed in some way so that it can be analyzed and/or processed to provide the data of particular interest. For some cases such as simple measurements of the A‐weighted sound pressure level, only limited amounts of processing are needed. In other cases with more sophisticated measurements, special analysis and processing is required. Such examples include modal analysis, sound intensity, wavelet analysis, machinery condition monitoring, acoustical holography, and beamforming, with which quite complicated signal analysis and processing may be needed. In all cases considerable care should be taken to ensure that the transducers together with their measurement systems are calibrated and checked periodically to make sure they are working properly.

7.2 Typical Measurement Systems

It may be necessary to measure noise and/or vibration for various reasons. Before beginning any measurement program, the objectives should be defined. For instance, it may be desired to measure noise to determine if a noise problem exists, whether the noise output of a machine is within its specifications, to determine the main ...