Ultrasound Techniques for Characterizing Liquids.I.Broad-Band Spectrometers

This tutorial gives a short introduction into the broad-band ultrasonic spectroscopy of liquids. The fundamentals of acoustical methods are summarized. Preference is given to methods using continuous waves and pulse modulated signals. Related techniques, such as time-domain methods with step-like excitation of the sample and with optical monitoring of acoustical waves (Brillouin scattering), are briefly mentioned, too. Constructions of some types of sonic cells for liquids and electronic set-ups for spectral measurements are presented in detail. The merits and limitations of different techniques of measurements, covering the frequency range from almost 10 kHz up to nearly 10 GHz, are discussed. Together with applications in the relaxation properties of liquids, examples of broadband ultrasonic spectra are shown.