What is the purpose of 'http://jitsi.org/jitmeet/audio ths Url

Jitsi using this url inside below function
muteParticipant(jid, mute) {
logger.info(‘set mute’, mute);
const iqToFocus = $iq(
{ to: this.focusMucJid,
type: ‘set’ })
.c(‘mute’, {
xmlns: ‘http://jitsi.org/jitmeet/audio’,
jid
})
.t(mute.toString())
.up();

    this.connection.sendIQ(
        iqToFocus,
        result => logger.log('set mute', result),
        error => logger.log('set mute error', error));
}

// mute-unmute-XX - Added unMuteParticipant method and changed onMute method.
unMuteParticipant(jid, mute) {
    logger.info('set unmute', mute);
    const iqToFocus = $iq(
        { to: this.focusMucJid,
            type: 'set' })
        .c('mute', {
            xmlns: 'http://jitsi.org/jitmeet/audio',
            jid
        })
        .t(mute.toString())
        .up();

    this.connection.sendIQ(
        iqToFocus,
        result => logger.log('set mute', result),
        error => logger.log('set mute error', error));
}

so what’s the purpose of it, please let me know because it output coming like “set mute error”