The so-called thermal-acoustic oscillations (TAOs) may appear under certain conditions in heated channels with the boiling coolant subcooling below the saturation temperature [102,103]. Much work, mostly experimental, has been dedicated to these oscillations. In this chapter, we shall refer to the work in which a heated channel (generally, an electrically heated tube) was acoustically isolated (acoustically open) from other components of the test facility. This was mainly achieved by locating vessels at the channel inlet and outlet. With their volumes, the vessels ensured acoustic channel isolation due to coolant compressibility. That is, equal pressure was provided upstream and downstream from the channel in the case of spontaneous initiation of the flow parameters’ high-frequency oscillations of an acoustic nature.