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Biamp Systems

System Design Template - Google Hangouts Meet Training/All Hands Space with Beamtracking Microphones

This Google Certified design template shows how Biamp Tesira TCM-series AVB Beamtracking™ Ceiling Mics can be paired with a Google Hangouts Meet kit to support a large training room/ all hands space. In this document, a large training room is defined as a learning space about 50' x 30' with around 30 - 60 participants. HID communication between the Google Hangouts Meet system and the Tesira EX-UBT USB interface provides a truly integrated experience with USB connection status and mute status feedback passing through to the TCM-1 pendant microphones.

Room design

Room Functionality Scope:System Diagram - GHM Training.png

  • Six ceiling pendant microphones withbeamtracking technology
  • USB connection to Google Hangouts Meet Kit
  • Ceiling speakers for playback of local presentation and far end audio sources
  • Podium microphone for both conferencing and local voice reinforcement
  • Two Wireless Microphones for both conferencing and local voice reinforcement










Equipment list

Below is the list of Biamp equipment used in this project:

  • 1 - TesiraFORTÉ AVB CI            12 mic/line level inputs with AEC; 8 mic/line level outputs
  • 2 - Tesira TCM-1A                      AVB beamtracking ceiling microphone, with integrated 2-CH amplifier
  • 4 - Tesira TCM-1 EX                  Extension beamtracking ceiling microphone
  • 2 - Tesira AMP-450P                  4-CH PoE+ amplifier providing 4 x 50 Watts burst power    
  • 1 - Tesira EX-UBT                      USB over AVB interface, supporting up to 8 channels of configurable USB audio and Bluetooth wireless technology

Note that other non-Biamp equipment is required, such as an AVB capable network switch, podium microphone, wireless microphones, loudspeakers, and Google Hangouts Meet Kit hardware.

Networking details

This application will make use of PoE+ powered endpoints which connect to the TesiraFORTÉ AVB CI and exchange AVB audio and control data. Regarding cable types and lengths, the common rules to gigabit Ethernet cabling do apply. The simplest way to realize a functioning system is using a converged single cable network on one AVB switch as shown in the drawing above. For a detailed guide on this, and the range of other supported network topologies, it would be helpful to reference this article.

Setup Requirements:

  • Use an AVB-enabled network switch with sufficient number of ports (6) and PoE+ (IEEE802.3at) support to interconnect all devices.  
    • Optional 802.3at (Class 4) PoE+ injector for powering each the EX-UBT, AMP-450P, and the TCM-1A
  • A standard network cable (Cat.5 or higher) to connect the TCM-1A with the TCM-1EX extension microphones.
    • Do not exceed 33ft or 10m on this link
    • This is a proprietary digital audio link, not compatible with Ethernet
  • Note that the TCM-1A, EX-UBT, and the AMP-450P use Layer 2 AVB for audio and control data, IP address setup is not required.

Once the required control and AVB connections are made, you will now be ready to send your compiled system configuration to the hardware.

System configuration

GHM All Hands.pngThe example file for this system design template is set up with all the audio I/O, processing, and control points required, and is ready to load to the system and begin setting up the room gain structure and EQ. In the file, the matrix routing is already in place to support the room design requirements. Nine AEC processing channels on the TesiraFORTÉ AVB CI will be occupied by the six TCM-1 microphones, two wireless microphones, and podium gooseneck microphone. The first analog audio input is used for the podium microphone. Analog inputs 3 and 4 are used for the wireless microphones. The eight loudspeakers will be connected across the two AMP-450Ps. 

To support the conferencing needs of the space, the microphone signals are routed to the USB output. All AEC references have been made in the matrix mixer for proper echo cancelation of the far end audio. The file's Equipment Table is populated with proper hardware to match the layout, but will need to have serial numbers and proxy host assignments added before loading the file to system.

The .zip file below contains the example Tesira configuration files for this conference room application.

Google Hangouts Meet Training/All Hands

Setting the audio device from Google Hangouts Meet

Once the configuration file has been loaded to the system, the EX-UBT will be available as an audio peripheral device from the Google Hangouts Meet user interface. To select the EX-UBT, navigate to the Settings menu on the Google Hangouts Meet user interface.


From the Audio menu, use the Microphone and  Speaker dropdowns to select the EX-UBT.


HID communication logic

The EX-UBT synchronizes privacy mute state and volume control when connected to the Google Hangouts Meet kit. This is achieved through Human Interface Device (HID) communication. Within the running Tesira configuration, room level control from the Google Hangouts Meet user interface will sync with the level control in the USB Input block, while privacy mute from the Google Hangouts Meet user interface will sync with the mute control in the USB Output block.

By default, the Google Hangouts Meet volume control will set to 60% when a meeting is started. This level will be reflected in the EX-UBT USB Input block.

clipboard_e73a31d023e3af9848cf62d174970ffa5.png USB Input Block Live.png

The privacy mute control on the Google Hangouts Meet user interface provides visual feedback to participants in the room by setting the TCM-1 microphone LEDs to green when unmuted and to red when muted. Mute state logic from the USB Output block is used to trigger presets that drive this LED color change.

GHM Large Logic.png

The USB Input and Output blocks also report current USB status for when an active USB connection has been made and when audio is streaming. This configuration file uses the connected and streaming logic outputs to enable the TCM-1 microphone LEDs. When not in a meeting the LEDs will be off. Once a meeting is started the LEDs will turn on.

Microphone and speaker placement 

The room

Arguably the single most important element in a conference system is the room itself. A noisy and reverberant room will generally sound awful for conferencing. A properly designed room with controlled reverberation and low noise floor will generally sound good for conferencing.

The importance of creating a controlled acoustic environment cannot be overstated. It is important to make the room as quiet as possible (lower noise floor) and minimize reverberance (shorter RT60) in preparation for installing the conferencing system. When properly applied, soundproofing and acoustic treatments will yield dramatic improvements in performance for most rooms.

Microphone placement

Even though the TCM-1 beamtracking microphones use state of the art technology to track a person's voice, while reducing unwanted background noise, the laws of physics GHM Large 33x14 7' Fair Elevation.pngcan't be ignored when deciding on the right placement of a microphone. A good signal-to-noise ratio is key in every part of the audio signal chain and for a typical microphone pickup scenario, this translates to avoiding large distances between the mic and the talker. The TCM-1 Calculator will help to find the right pendant height and required distance between the two pendants for the the expected coverage area. Here are a few more tips to an ideal microphone placement:

  • Keep the distance to the talker as short as possible.
  • Keep the distance to the ceiling speakers as high as possible.
  • Stay away from noise sources like projector fans and air vents.


Speaker placement

Placing speakers in a room can be as equally critical as finding the right spot for a microphone. An ideal positioning of multiple ceiling speakers will achieve an even SPL coverage and a good speech intelligibility across the entire room. In order to get a better sense on how much SPL the speaker of choice is able to produce with the given power of our AMP-450P amplifier, the Amplifier Power Calculator will provide some answers. In addition to that, a speaker simulation software might be able to predict the expected in-room STI values.

In this example, the speakers are not being used for voice-lift or similar live speech reinforcement, hence gain before feedback doesn't have to be considered. Still, avoiding short distances between the speakers (far-end audio) and the microphone will help to improve the AEC performance.

Audio setup

  • Follow Gain Structure best practices to set input and output levels of microphones and sources. Input and output gain levels have been left at default settings for integration flexibility of the file. Input and Output metering has been added to assist with setting gain structure within the file. Additional meters can be added to the file as required to allow for additional detail at point along the signal path.
  • Reference AEC best practices documentation and begin to join some test meetings with the system. ERL values between 0dB and +15dB are optimal.
  • Uber Filters have been added to signal paths to allow for any additional equalization as needed. It is recommended to use the advanced filters section of the AEC channel processing block for any high pass filtering needed on conference table microphone inputs. Additional filtering or dynamics blocks may be added or changed as needed to achieve the desired results in the file.
  • Far end audio level and privacy mute will all be controlled from the Google Hangouts Meet Kit user interface.
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