In this case, it sounds as if you are experiencing a "phase" issue with your headphones.
To troubleshoot them effectively, please observe the following:
1. Please make certain that your headphones are fully inserted, and that there is nothing (such as a protective-covering) preventing the connector from being fully inserted.
2. Please try the headphones on a different device that supports a headphone connection (such as a smartphone, .MP3 player, etc.). When doing so, please observe the above. If the headphones work on the other device, then there is nothing wrong with your headphones.
If you are still experiencing an issue with your headphones after trying the above, you will have two options:
1. Exchange the headphones at the dealer you purchased, pending their policy.
2. Send them to the Audio-Technica Service Department. For information on obtaining Service with ATUS, please visit www.audio-technica.com/service