Voice Activity Detection

The Cornerstone Classroom App client and the Express client, both support the Voice Activity Detection feature.

Attention: This feature is enabled by default. To disable the feature, submit a request. For more details, contact Support.


Voice activity detection is the ability of the internal voice engine to detect when a user is speaking. When voice activity detection support is enabled, audio is transmitted on a channel only when an activity is detected on the microphone.

For example, if there are 15 users in a session with some using the latest version of the App and others using the Express client, then all 15 users can have the microphone. The microphone is ready to detect voice activity as soon as a user unmutes their microphone the first time. After that, when they start speaking, they will be audible in the event. To avoid transmission of background audio in the session, users can use the mute button on their headsets to mute the audio. To speak again in the session, they can simply press the mute button on the headset again.

Voice activated App clients can interoperate in a session with older App clients that do not support voice activity detection. Users with the older version of App client do not have voice activity detection enabled microphone option available to them. They need to press the microphone button in the client to be audible in the session each time.

Although, all users in a session can have the voice activated microphone (in the Inactive state), only up to 10 microphones can be active in the session simultaneously. For more details, see Set concurrent speakers for an event.

Enable voice activity detection support

This feature is enabled by default.

Only Cornerstone Classroom administrators can configure your domain to disable voice activity detection support.

Note: To use the voice activity detection feature on the Cornerstone Classroom App, end users need to update the version of the App client installed on their system. If users are on the Express client, then the feature is available by default and they don't need to take any additional action.

Mic behavior with voice activity detection enabled

When voice activity detection is enabled, the participant's microphone is muted by default at the beginning of a Cornerstone Classroom session. This is indicated to the participants by the following brief start-up message.

Figure 1. Start-up message
Start-up message

Participants must manually click the mic icon to unmute the mic. Once the mic is unmuted, it remains inactive until it detects a voice.

The changes in mic states and their corresponding mic icons for both App and Express clients are indicated in the following table:

Table 1. Mic states and icons when Voice Activity Detection is enabled
Mic State Scenario Mic icon (App client) Mic icon (Express client)

Mic is disabled

Leader has taken the mic away. For example, at the beginning of a class event.

Mic is enabled/muted

Client has mic, but is muted

Mic is enabled / unmuted / inactive, where inactive = 'not talking'

Client is not talking ('Voice Activated' state)

Mic is enabled/unmuted/active, where active = 'talking'

Client is broadcasting audio

Note: Muting the microphone on the headset stops the audio from broadcasting. However, it does not impact the mic icon state. It remains in the 'Voice Activated' state rather than changing to the Muted icon.