Nada

“Sound”. In haṭha yoga, the subtle inner sound heard during deep meditation. The fourth chapter of the HYP is dedicated to nādānusandhāna (absorption in nāda).

Types of nāda:

• Āhata: “Struck” sound, produced by contact (all ordinary sounds)
• Anāhata: “Unstruck” sound, arising without external cause (the inner nāda)

Progression of nāda according to the texts:

1. Sounds like ocean, thunder, drums
2. Sounds like bells, conches, gongs
3. Sounds like flutes, vīṇās, bees
4. Sound becoming increasingly subtle until merging into silence

The practice of listening to nāda (using techniques like Bhrāmarī or Ṣaṇmukhī mudrā) leads the mind toward laya (dissolution) and samādhi.