This is twang sound coming from the stretched Gandiva of Savyasanchi (Arjuna). These arrows shot by Arjuna are very acute and killing ceaselessly the enemies.
एतत् कूजित गाण्डिवंन विसृष्ट सव्यसाचिना। एते हस्तवता मुक्ता मन्त्यमित्राशिताः शराः॥