excerpt from the article of "psychology today":

Sound has an ancient kinship with meditation and healing. Sound healing has ancient roots in cultures all over the world, including Australian aboriginal tribes who used the didgeridoo as a sound healing instrument for over 40,000 years to ancient such as Tibetan or Himalayan singing bowl spiritual ceremonies. Sound meditation is a form of focused awareness type of meditation. One kind that has become more popular is called “sound baths,” which uses Tibetan singing bowls, quartz bowls, and bells to guide the listener. These practices highlight themes of how the experience of sound manifests not only through hearing but through tactile physical vibrations and frequencies.

Science is still catching up to understanding how sound heals, but the current research is promising. A review of 400 published scientific articles on music as medicine found strong evidence that music has mental and physical health benefits in improving mood and reducing stress. In fact, rhythm in particular (over melody) can provide physical pain relief. 

One study published in the Journal of Evidence-Based Integrative Medicine found that an hourlong sound meditation helped people reduce tension, anger, fatigue, anxiety, and depression while increasing a sense of spiritual well-being. The sound meditation used a range of Tibetan singing bowls, crystal singing bowls, gongs, Ting-shas (tiny cymbals), dorges (bells), didgeridoos, and other small bells. The main instrument used was the singing bowls for 95% of the session. People who had never done sound meditation experienced significantly less tension and anxiety afterward, as well as those who had done it before.