The HTC Vive headset has a 3.5mm headphones’ output.
Connect the provided AUX cable - one side to the HTC audio output, and the other side to the Woojer Strap audio input jack. Connect your headphones to the Strap audio output jack.
On your PC - go to "sound settings" and make sure your main sound card is set to HTC VIVE.
Otherwise, the audio will be routed to the default speakers.
Note: please remember to always set your audio source to MAX volume.
Steam VR users: For using Strap and VR headphones simultaneously with a wireless connection, please refer to this article.