![]() Since the model gives an explicit functional form for M, it is possible to use Eq. The argument, t, is the time delay at which the noise is observed and can be related to a spatial position within the material. In that model for the backscattered noise generated by a tone burst, the grain noise is described by following equation (1) N(t)=FOM×M(t) where N(t) is the rms grain noise, FOM is a material characteristic parameter and M is a factor that depends on the detailed description of the experimental configuration as well as the ultrasonic attenuation. As an aid to understanding the grain noise, an independent scattering model was constructed and studied during last two years by Margetan and Thompson. Therefore better understanding of grain noise is required to quantify and increase the detectability of the small flaws. The noise introduces problems in detecting small flaws, such as hard-alpha inclusions, by forming a background which can mask the flaw signals. The complex microstructure of two-phase titanium alloys can produce considerable ultrasonic backscattering noise.
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