S U M M A R YResonant Ultrasound Spectroscopy (RUS) uses normal modes of elastic bodies to infer material properties such as elastic moduli and Q. In principle, the complete elastic tensor can be inferred from a single measurement. For centimeter-sized samples RUS fills an experimental gap between low-frequency stress-strain methods (quasi-static up to a few kHz) and ultrasonic time-delay methods (hundreds of kHz to GHz). We use synchronous detection methods to measure the resonance spectra of homogeneous rock samples. These spectra are then fit interactively with a model to extract the normal-mode frequencies and Q factors. Inversion is performed by fitting the normal-mode frequencies. We have successfully applied this technique to a variety of isotropic and anisotropic samples, both man-made and natural. In this paper we will show in detail the procedure applied to a cylindrical core of Elberton granite. By means of a statistical fit of the measured normal modes and an independent laser ultrasonic measurement, the granite core was inferred to have orthorhombic symmetry. A 10 per cent P-wave anisotropy was measured in the plane perpendicular to the core axis. Laboratory measurements of elastic propertiesMechanical methods for measuring the elastic properties of laboratory specimens are divided into three types: quasi-static, resonance, and time-of-flight. Those types reflect the ratio of the wavelength of the mechanical signals used to the size of the specimen under test.Quasi-static methods, such as cyclic loading (Batzle & Wang 1992), subject the sample to deformations that are slow compared to any of its natural mechanical resonances, so that the sample is close to mechanical equilibrium at all times during the test. By measuring both the applied stresses as well as the strains induced we hope to infer the sample's elastic compliances; if we think of stress, strain, and compliance as complex functions of frequency, we can see that the phase of the compliance (which follows from the phase shift between stress and strain) tells us about sample anelasticity. Cyclic loading measurements can be made from frequencies of the order of 10 3 Hz (above which the typical apparatus tends to become animated) down to zero frequency and have the geophysically attractive property that they can be made at frequencies which overlap those of exploration (at least) seismology. The most serious limitations of this technique are the difficulty of accurately accounting for the complex mechanical behaviour of the measurement apparatus and of making accurate, low-noise strain measurements at low frequencies.Resonance techniques measure the frequencies of the specimen's elastic resonances, or free oscillations. These frequencies reflect the size, shape, and elastic composition of the sample; each corresponds to a particular bundle of bouncing, interconverting traveling waves which conspire to exactly repeat at intervals of 1/f , where f is the resonance frequency. Given a sufficient data set of observed resonance frequencies we can mak...

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Some experiments are conveniently performed in the time domain, some in the frequency domain, and some use a hybrid approach. Does the domain make any difference in the ultimate resolution of the experiment? Or can the details of the experiment always be tweaked so that the different approaches give the same answer? We consider a simple optics experiment and consider both time and frequency measurements and take into account the influence of noise, finite dynamic range, attenuation, and the duration of the measurement.

We demonstrate 260 GHz (λ=1.15 mm) near field imaging using a conical Teflon probe whose tip protrudes through an aperture in a tapered aluminum holder. The imaging system is based on a quasioptical millimeter wave vector network analyzer. We present a variety of different imaging examples of dielectrics and metals, in both reflection and transmission modes, as well as an analysis of interesting diffraction and scattering effects observed in some of the images. The probe has an approximate tip diameter of 0.17 mm and an aperture size of about 1 mm. We observe horizontal resolution ranging from 0.2–0.5 mm depending on the sample being imaged.