Acoustic measurement methods

This paper intends to give, through different examples, guide-lines for characterization of array probes. We discuss, particularly, beam pattern measurement methods and raise the question whether it is useful to achieve a full characterization of all beams steered by the probe or to limit the characterization to a minimum set of acoustic configurations. An automatic bench for full characterization of tube inspection probes is described. 

Acoustic Measurements. Measurement of the propagation of ultrasonic acoustic waves has been found useful for determining the viscoelastic properties of thin films of adhesives. In this method, the specimen is clamped between transmitting and receiving transducers. The change in pulse shape between successive reverberation of the pulse is dependent on the viscoelastic properties of the transmitting material. Modulus values can be calculated (267,268). 

So, partial discharge measurements have become a well-established method for type and routine testing as a non-destructive material test and quality control [23], [26], [53]. Apart from optical and acoustical detection methods of partial discharges, the high frequency detection and measuring method preferably covers a wide range of applications. It will be considered in more detail in the following. 

E.P Papadakis, Ultrasonics Measurement Methods, Physical Acoustics, Vol. XIX, Academic Press, New York, 1990, p. 107. 

The method applied to measure the depth of the ablated area or the removed mass can also have an influence on the ablation parameters. If profilometric measurements (optical interferometry, mechanical stylus [34], or atomic force microscopy [35]) are used to calculate the ablation rate, a sharp ablation threshold can be defined. This is also supported by reflectivity [36] and acoustic measurements [37], In mass loss measurements, such as mass spectrometry or with a quartz crystal microbalance (QCM), the so-called Arrhenius tail [38] has been observed for certain conditions. The Arrhenius tail describes a region in the very low fluence range, where a linear increase of detected ablation products is observed, which is followed by a much faster increase, that coincides with removal rates of the profilometric measurements [39]. 

Lu and Lewis [76] proved the excellent performance of Miller and Bolefs continuous acoustic wave analysis for mass loads up to ntf / mq < 25%. It is easy to show that Behrndt s eqn. (8) of the period measurement method and Sauerbrey s eqn. (6) of the frequency measurement method are approximations of Miller and Bolefs eqn. (7) for small mf / mq values. 

Acoustical properties of soybeans can be used to help distinguish between healthy and diseased soybeans. Misra et al. (1990) measured acoustic properties of soybeans by transmitting sound waves through soybeans using acoustic transmission and by an impact force method. In the impact force method, a seed is dropped on an acoustic transducer creating an impulse wave. The acoustic transmission method was slow but was able to predict the mass of individual soybeans. The impact force method showed that diseased soybeans had a narrower bandwidth than healthy soybeans. Soybeans with wrinkled surfaces and diseased and damaged soybeans were detected from healthy soybeans based on wide variations at low frequencies. 

Modulus of rupture, MOR. was obtained on polished samples by four point bend tests (4 X 20 mm) with 1 mmmin deformation rate using Instron equipment. The elastic modulus, E, was measured at room temperature, by the acoustic resonance method using a self-assembled apparatus and, at high temperature, from the stress-strain curve obtained in the four point bend tests. 

Colin [1] has reviewed some measurement methods in microscale flow, including the weighing method, thermal method, wave reflection method, acoustic vibration method, and so on. Here, two common methods, the weighing and displacement methods, are introduced. In the weighing method [2], the total mass M of fluids flowing out within a time At are measured, and the flow rate is calculated as... 

CEN EN ISO 11819-1. 2001. Acoustics - Measurement of the influence of road surfaces on traffic noise - Part 1 Statistical pass-by method. Brussels CEN. 

Figure 33.4. Measurement method for obtaining acoustic velocities.

Figure 11.1.2 shows the measuring method of the cracking load [ 7]. A silicon nitride flat plate and a silicon nitride ball were used as test materials. The cracking load was decided by detecting acoustic emissions while gradually adding a load to the test pieces. Three kinds of balls, 5/32, 5/16 and 3/8 in., were used in this test. 

In this chapter, we summarize our general review of gas-water two-phase flow characteristics in the surf zone. There are several measurement methods for the aeration in the surf zone, such as in situ measurements, video or photographic measurements, laser measurements, and acoustic measurements. There is no one appropriate method to measure the volume of air and bubbles in the surf zone. The spatial and temporal characteristics of void fraction are summarized, and the bubble size distribution is described with simple theories. Furthermore, the gas transfer prediction method is presented as a function of the bottom slope and wave characteristics for the surf zone waves. 

The great challenge in binaural technology is to devise a practical method by which binaural signals can be individualized to a specific listener. There are several possible approaches to meeting this challenge acoustic measurement. 

Picard, M.A., Solana, R, Urchuegfa, J.F., 1998. A method of measuring the dynamic flow resistance and the acoustic measurement of the effective static flow resistance in stratified rockwool samples. J. Sound Vib. 216 (3), 495-505. 

Nestleroth et al. [15], Segal et al. [16] considered some established novel signal processing schemes to assist in adhesive bond inspection. Sinclair et al. [17] and Filimonov [18] employed acoustic resonance methods for dynamic elastic modulus measurements in adhesively bonded structures. Yost and Cantrell [19], Achenbach and Parikh [20] and Nagy et al. [21] considered a nonlinear response of bonded structures to estimate material characteristics. In Achenbach and Parikh [20], failure was preceded by nonlinear behavior of thin boundary layers at the interfaces. Billson and Hutchins [22] considered lasers and EMATS in bond investigations. It was shown that this non-contact technique was reasonable when compared to that obtained by conventional piezoelectric transducers. Ince et al. [23] also characterized bonds with laser-generated ultrasound and through-transmission measurements. 

Sinclair, A.N., Dickstein, P.A., Spelt, J.K., Segal, E. and Segal, Y, Acoustic resonance methods for measuring dynamic elastic modulus of adhesive bonds. In Dynamic Elastic Modulus Measurements in Materials. ASTM STP 1045, 1990, pp. 162-179. 

ISO 13472-2, 2010. Acoustics— Measurement of sound absorption properties of road surfaces in situ - Part 2 Spot method for reflective smfaces. International Organization for Standardization. 

The measured skin hardening or softening also varies with methods of detection. For instance, the modulus of nanocrystalline of 50-800-nm-thick Ni films, measured using acoustic AFM [35], is lower than that of the bulk, as no artifacts such as accumulation of dislocations are involved in the non-contact acoustic AFM method. SiTiN films are measured approximately 10-20 % harder using nanoindentation than the values obtained using SAWs methods [36]. The additional pressure due to compression will cause deviation of the intrinsic values. Therefore,... 

Jemielniak R. and Pilecki Sz. Measurement of moduli of elasticity and of internal friction using the acoustic resonance method. Transactions of the Conference "Electric and Acoustic Methods of Material Testing", Jablonna 1983 Cin Polish. ... 

Fig. 14. Schematic views of (a) manifestation of transitions in a DMA spectrum, and (b) frequency dependencies of transition temperatures in polymers, measured by various techniques I, DSC, mechanical relaxation, radiothermoluminescence, thermostimulated depolarization II, mechanical and dielectric relaxation III, dielectric relaxation, NMR IV, ESR (probe method), Mandelstam-Brillouin scattering, acoustic measurements (From Ref 140),...

Quantitative data (i.e., velocities of surface acoustic waves) obtained by a spherical lens, which is commonly used for acoustic imaging, may not be expected to provide information on the elastic anisotropy of materials. A cylindrical lens (i.e., line-focus lens) and a measuring method were developed to overcome this issue. This technique is especially useful when the substrate is anisotropic in the nanoscaled thin film system. 

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