Here's a rubber gasket, sealing the area around the headphone jack—presumably for protection from water damage.

The headphone jack's home is a blobular mess of a cable, akin to the iPhone's front-facing camera and sensor cable—with the noteworthy exception of the Alpha's front-facing camera living on its own.

On the Alpha's cable, we find the headphone jack, earpiece speaker, microphone, volume button switches, and an ambient light sensor.