The subwoofer on the Goodmans GDSBT150OP is equipped with a signal sensing auto-standby feature which reduces it's power consumption. If there is a quiet period where no low frequencies are being played, the subwoofer may go into a power saving standby mode. It is possible that when it turns back on again there may be a slight pop noise depending on the audio signal being transmitted at the time.
Here are some tips to reduce this:
1. Increase the volume on the television and reduce volume on the sound bar. This will increase the signal level into the subwoofer's auto-standby system.
2. If the GDSBT150OP is connected with the Digital Optical cable see if you can switch your televisions Optical Output setting to PCM instead of AUTO. Consult your TV's User Guide.
3. Try to route the subwoofer connection lead away from any other electronic devices.