NASA Scientific and Technical Aerospace Reports

Since the early 1980s, the authors have collected nearly 800 cores at 69 shallow-water sites around the world (12
calcareous and 57 siliciclastic sites). Siliciclastic sites ranged from soft mud through coarse sand and calcareous sites consisted
of molluskan shells, shell hash, carbonate reef debris, and calcareous particles formed by chemical precipitation. The cores
were carefully collected by divers from shallow water or sub-sampled from box core samples retrieved from deeper waters.
For most sediment samples compressional wave speed and attenuation (at 400 kHz) were measured at 1 cm intervals and
sediment physical properties (porosity, bulk density, grain density, and grain size distribution) were determined from 2cm-thick
sections from the same core. Data are typically restricted to the upper 30 cm of sediment. Based on the nearly 4500
common data points resulting from core measurements (3922 siliciclastic and 621 calcareous) regressions were determined
among sediment physical and acoustic properties.
DTIC
Acoustic Properties; Sediments
20040112031 NASA Glenn Research Center, Cleveland, OH, USA
Computation of Tone Noises Generated in Viscous Flows
Loh, Ching Y.; Jorgenson, Philip C. E.; 2004; 16 pp.; In English; Fourth Computational Aeroacoustics (CAA) Workshop on
Benchmark Problems, 20-22 Oct. 2003, Cleveland, OH, USA
Contract(s)/Grant(s): 781-30-46; No Copyright; Avail: CASI; A03, Hardcopy
Three benchmark problems from the current and previous CAA workshops involving tone noise generated in viscous
flows are investigated using the CE/SE finite volume method. The CE/SE method is first briefly reviewed. Then, the
benchmark problems, namely, flow past a single cylinder (CAA Workshop II problem), flow past twin cylinders (from the
current CAA Workshop IV, Category 5, Problem 1) and flow past a deep cavity with overhang (CAA Workshop III problem)
are investigated. Generally good results are obtained in comparison with the experimental data.
Author
Cavities; Finite Volume Method; Space-Time Ce/Se Method; Viscous Flow; Conservation Laws; Aeroacoustics
20040121066 NASA Langley Research Center, Hampton, VA, USA
AE Source Orientation by Plate Wave Analysis
Gorman, Michael R.; Prosser, William H.; Journal of Acoustic Emission; 1991; Volume 9, No. 4, pp. 283-288; In English;
Original contains black and white illustrations; No Copyright; Avail: CASI; A03, Hardcopy
Lead breaks (Hsu-Neilsen source) were used to generate simulated acoustic emission signals in an aluminum plate at
angles of 0, 30, 60, and 90 degrees with respect to the plane of the plate. This was accomplished by breaking the lead on slots
cut into the plate at the respective angles. The out-of-plane and in-plane displacement components of the resulting signals were
detected by broad band transducers and digitized. Analysis of the waveforms showed them to consist of the extensional and
flexural plate modes. The amplitude of both components of the two modes was dependent on the source orientation angle. This
suggests that plate wave analysis may be used to determine the source orientation of acoustic emission sources.
Author
Acoustic Emission; Waveforms; Lead (Metal); Displacement; Plane Waves
20040121078 NASA Langley Research Center, Hampton, VA, USA
Exploratory Study of the Acoustic Performance of Piezoelectric Actuators
SantaMaria, O. S.; Thurlow, E. M.; Jones, M. G.; [1989]; 6 pp.; In English; Original contains color illustrations; Copyright;
Avail: CASI; A02, Hardcopy
The proposed ducted fan engine has prompted the need for increasingly lightweight and efficient noise control devices.
Exploratory tests at the NASA Langley Research Center were conducted to evaluate three piezoelectric specimens as possible
control transducers: a Polyvinylidene Flouride (PVDF) piezofilm sample and two composite samples of Lead Zirconate
Titanate (PZT) rods embedded in fiberglass. The tests measured the acoustic output efficiency and evaluated the noise control
characteristics when interacting with a primary sound source. The results showed that a PZT sample could diminish the
reflected acoustic waves. However, the PZT acoustic output must increase by several orders of magnitude to qualify as a
control transducer for the ducted fan engine.
Author
Piezoelectric Actuators; Control Equipment; Sound Transmission; Sound Waves
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