Application of dynamic signal analyzers to selected electroacoustical measurements.

Abstract

Modern dynamic signal analyzers incorporating a variety of digital signal processing techniques and excitation source types are now sufficiently accurate to be used in many precision measurement situations for which much more labor-intensive methods previously have been necessary. Such use typically requires well-designed analyzers for which individual electrical components and system performance have been well characterized, and may require performing the same type of measurement several times with different choices of analyzer setup parameters, involving different tradeoffs among measurement uncertainty components. Validation of analyzer measurement results by comparison with results of established techniques is often necessary. These analyzers also can provide new ways to examine the individual influences of some measurement uncertainty components that have been notoriously difficult to quantify. Such components include those attributable to imperfections in anechoic chambers, and to unwanted scattering and diffraction effects of instrument structures. Specific examples to be considered include preliminary measurements of free-field phase characteristics at low frequencies in the large NIST anechoic chamber, and the effects of chamber imperfections and of slight standing waves between opposing microphone diaphragms during free-field calibration by reciprocity at essentially normal incidence in the small NIST anechoic chamber at frequencies up to 100 kHz.