Abstract: The acoustic wave generated by sudden thermal stress is used to obtain information non-invasively on the composition and structure of the stressed body. One or more acoustic transducers (1 and 1') are coupled with the surface of the body to intercept the acoustic wave and generate a corresponding electrical signal. The sudden thermal stress is induced by a pulse of radiation which deposits energy causing a rapid, but very small, rise of temperature. The radiation may be ionizing radiation, such as high energy electrons, photons (X-rays), neutrons, or other charged particles. The radiation may also be non-ionizing radiation, such as RF(2) and microwave electromagnetic radiation (3) and ultrasonic radiation (4). The electrical signal from the acoustic transducer (1) is amplified (5) and supplied to a digitizer (6), which provides a continuous stream of digital words corresponding to samples of the amplified signal.

Abstract: Passive non-invasive temperature measurement of the interior of a body is accomplished by using the acoustic thermal noise spectra of the body. One or more acoustic transducers are coupled with the surface of the body to intercept the acoustical noise signal from within the interior of the body along well defined paths to generate a corresponding electrical signal. The noise power spectrum of the electrical signal is analyzed by means of a power spectrum analyzer to develop an output representing the temperature-depth distribution along said paths. The output of the power spectrum analyzer may be displayed and/or recorded or subjected to further signal processing.