The TS_SOUND_CAPABILITYSET structure advertises the ability to play a "beep" sound. This capability is only sent from client to server.
file:///C:/ts_dev/TestSuites/MS-RDPBCGR/TestSuite/Src/TD/latest_XMLS_16may/RDPBCGR/ _rfc_ms-rdpbcgr2_1_6_1_12.xml
        public void AddSoundCapSet()
        {
            TS_SOUND_CAPABILITYSET soundCapSet = new TS_SOUND_CAPABILITYSET();

            soundCapSet.capabilitySetType = capabilitySetType_Values.CAPSTYPE_SOUND;
            soundCapSet.lengthCapability = (ushort)Marshal.SizeOf(soundCapSet);
            soundCapSet.soundFlags = soundFlags_Values.SOUND_BEEPS_FLAG;
            m_arrCapSet.Add(soundCapSet);
        }
 /// <summary>
 /// 2.2.7.1.11
 /// Check the requirements in structure TS_SOUND_CAPABILITYSET.
 /// </summary>
 /// <param name="sound">The TS_SOUND_CAPABILITYSET structure.</param>
 public void VerifyStructure(TS_SOUND_CAPABILITYSET sound)
 {
     site.CaptureRequirementIfAreEqual<capabilitySetType_Values>(capabilitySetType_Values.CAPSTYPE_SOUND, sound.capabilitySetType,  1387,
         @"In TS_SOUND_CAPABILITYSET structure, the capabilitySetType field MUST be set to CAPSTYPE_SOUND (12).");
 }