What are the sources through which the yogi can perceive nāda? There are two main ways. The first is mantra yoga (tantras), the second is haṭha-yoga (prāṇāyāma, mudrās, etc.). Here is what the Śāradā-tilakam tantra (Рrathamaḥ paṭalaḥ) tells us:
सच्चिदानन्दविभवात् सकलात् परमेश्वरात् ।
आसीच्छक्तिस्ततो नादो नादाद् बिन्दुसमुद्भवः ॥७॥
saccidānandavibhavāt sakalāt parameśvarāt ।
āsīcchaktistato nādo nādād bindusamudbhavaḥ ॥7॥
From the eternal goodness of Parameśvara, whose nature is Eternity-Knowledge-Bliss, Śakti (power) manifested first, then the vibration (nāda) manifested from the power, and bindu manifested from the peak of the tension of nāda.
That is, if you practice yoga, then by doing practices to activate Śakti, such as bhastrikā–prāṇāyāma, etc., Śakti can release the pulsation, the vibration of nāda. Or, if you practice mantras, then “activating the mantras“, awakening them in various ways, you will also come to the perception of nāda.
Of course, these methods in the traditions have always been directly transmitted from Gurus to their students. It is more than just information or theory, although knowledge of the theory, one way or another, can help.