From Chapter 12 ("Taking It Home") of Subtle Sound: The Zen Teachings of Maurine Stuart:

In the Surangama Sutra, the Buddha instructs us to enter samadhi, this deep, concentrated state of mind, from listening—starting with listening, being one with listening. Thich Nhat Hanh asks his students just to listen to the sound of the gong. Every so often he stops talking and just does this. (Gong is struck.) When we strike this gong we should let it sing down to its bottom drop, like this. It takes our zazen right down if your mind is with that sound, the whole body and mind with that sound. It's a most wonderful way to enter samadhi. So those of you who strike the gong, take your time. Don't go (gong is run three times in quick succession). No good. It sounds like a fire alarm. (Gong is rung once.) One clear sound. One pure, clear sound. No thoughts about whether that sound is soft or that sound is harsh or why didn't I strike this gong better or whatever. Just do it! Just listen. Just be here with the sound.

^z - 2017-05-09