From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Ἀκούω (Strong'S #191 — Verb — akouo — ak-oo'-o )

"to hear," is rendered "hearken" in the AV and RV, in  Mark 4:3;  Acts 4:19;  7:2;  15:13;  James 2:5; in the RV only, in  Acts 3:22,23;  13:16 (AV, "give audience");   Acts 15:12 , "hearkened" (AV "gave audience"). See Hear , No. 1. Note: In  Acts 12:13 , hupakouo, lit., "to hearken," with the idea of stillness, or attention (hupo, "under," akouo, "to hear"), signifies "to answer a knock at a door," RV, "to answer" (AV, "to hearken"). See Obey.

2: Ἐπακούω (Strong'S #1873 — Verb — epakouo — ep-ak-oo'-o )

denotes "to hearken to,"  2—Corinthians 6:2 , RV (see Hear , A, No. 4).

3: Ἐνωτίζομαι (Strong'S #1801 — Verb — enotizomai — en-o-tid'-zom-ahee )

"to give ear to, to hearken" (from en, "in" and ous, "an ear"), is used in  Acts 2:14 , in Peter's address to the men of Israel.

4: Πειθαρχέω (Strong'S #3980 — Verb — peitharcheo — pi-tharkh-eh'-o )

"to obey one in authority, be obedient" (peithomai, "to be persuaded," arche, "rule"), is translated "to hearken unto" in  Acts 27:21 , in Paul's reminder to the shipwrecked mariners that they should have given heed to his counsel. See Obey.

King James Dictionary [2]

HE`ARKEN, h`arken.

1. To listen to lend the ear to attend to what is uttered, with eagerness or curiosity.

The furies hearken, and their snakes uncurl.

2. To attend to regard to give heed to what is uttered to observe or obey.

Hearken, O Israel, to the statutes and the judgments which I teach you.  Deuteronomy 4

3. To listen to attend to grant or comply with.

Hearken thou to the supplication of thy servant.

50Kings 8.

HE`ARKEN, h`arken. To hear by listening. Little used.

Webster's Dictionary [3]

(1): ( v. t.) To hear by listening.

(2): ( v. t.) To give heed to; to hear attentively.

(3): ( v. i.) To inquire; to seek information.

(4): ( v. i.) To listen; to lend the ear; to attend to what is uttered; to give heed; to hear, in order to obey or comply.