Sound hitting a boundary splits into reflected and transmitted parts with no loss

Evidence

We are familiar with partial reflection of sound in the context of a pipe with a sudden change in diameter. There is no loss of sound energy, but rather the wave is split in two, one part transmitted and one part reflected. The reflected part initiates an echo with less energy than it started with, but the rest of the energy is in the transmitted wave. If you hear a conversation in the next room with the door shut, the sound coming through the wall represents transmitted energy, implying that the reflected energy suffered a reduction in intensity. — Eric J. Heller, Why You Hear What You Hear- An…, 2438