Test the headphones with a different audio input to determine if the issue lies with the headphones or the audio device. Bend the cable while listening to audio to identify any areas where the sound crackles or cuts out. If the issue is near the plug, inspect the plug for any signs of damage and consider fixing or replacing it. If the issue is along the cable, strip off the insulation and identify the broken or frayed wires. Splice the wires together and solder the connections for a secure repair. Slide shrink tubing over the repaired area and heat it to provide insulation and durability.