Calculator‐based digital system for underwater acoustical measurements

Three-dimensional underwater acoustical imaging

Development of a near-field acoustical holography system for aircraft jet source noise measurements

Military jet aircraft are exposing both ground maintenance personnel and the community to high levels of noise. The US Department of Defense is funding research to develop advanced modeling tools for noise reduction techniques and community noise exposure. For these tools to achieve their full potential, innovative measurement and analysis methods are necessary to characterize the jet noise sou...

Energy-Based Acoustical Measurements of Rocket Noise

Energy-based acoustical measurements are investigated in the context of more fully characterizing rocket noise source regions. Near-field measurements made on statically fired GEM-60 motors are described and the performance of two types of four-microphone tetrahedral probes is discussed. Vector intensity plots reveal the magnitude and directionality of the near-field sound radiation as a functi...

Digital Waveguide Modeling of Flared Acoustical Tubes

|The distributed re ection of the ared tube is calculated using the Schroedinger equation, including the e ects of viscothermal and open end radiation losses. The re ection is approximated with digital lters, which are designed to be e cient and accurate in a digital waveguide model of a wind instrument. Weighted Least-Squares design techniques are applied to model the re ectance of a Bessel ho...

Reciprocal maximum-length sequence pairs for acoustical dual source measurements.

In this paper we propose and demonstrate a method to obtain simultaneous dual source-receiver impulse responses in acoustical systems using binary maximum-length sequences (MLS). A binary MLS and its reversed-order sequence form a reciprocal MLS pair. Their correlation property includes a two-valued "pulse-like" autocorrelation function and a relatively smaller-valued cross-correlation function...