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The Sony WH-CH720N headphones represent the latest iteration of Sony's wireless headphone line, succeeding the WH-CH710N model. These over-ear, Bluetooth headphones are equipped with Active Noise Canceling (ANC), Passthrough, virtual surround sound, and multi-device pairing capabilities. They support both Bluetooth and auxiliary (Aux) connections.

At the University of Music Karlsruhe (HfM Karlsruhe), we required four wireless headphones for binaural headtracked audio applications in immersive VR and XR projects. We selected these headphones due to their low latency, Passthrough feature, and advanced Bluetooth technology.

During initial testing, we encountered an issue with the microphone's low input level. When recording or speaking, only very loud noises or direct contact with the microphone were audible. This problem was resolved through a software update provided by Sony, necessitating a reset of the headphones. To reset and update the headphones, press both the Bluetooth button and the middle button on the right side simultaneously until the Bluetooth indicator blinks four times. Further details can be found at the following link:

Pairing the headphones via Bluetooth is straightforward. Simply press the Bluetooth button for 5 seconds until the Bluetooth indicator light blinks. Below are images of the headphones, the case, and the included cables:

The WH-CH720N supports full-duplex audio, i.e. simultaneous audio output to the headphones (stereo) and audio input via the built-in microphone.

A number of scenarios are possible:

• Full-duplex with cables: We connected the headphones to a Y cable (one in two outs) with the provided AUX cable. Then we connected the two Y cable exits to an Headphone and Microphone to USB adapter. This way, the headphones worked bidirectionally, but only in mono.

• Full-duplex via bluetooth conection. On a phone and a mac, the bidirectionality did work, however, on an RPi, the bidirectionality was not possible. We are still testing all of the possibilities of bidirectionality with bluetooth.

• Bluetooth and cable (aux) simultaneously. Unfortunately, when the headphones were connected by a cable, the Bluetooth connection was not possible. For further information please follow this link