The following article provides information about Biamp's Parlé-series Beamtracking™ Microphones. It discusses some of the core technologies that make these microphones work, as well as the resources available in software for setup and configuration.
|TCM-X||Plenum network box + one ceiling-mount microphone array|
|TCM-XA||Plenum network box with built-in amplifier + one ceiling-mount microphone array|
|TCM-XEX||One expansion ceiling-mount microphone array|
|TTM-X||Under-table network box + one tabletop microphone array|
|TTM-XEX||One expansion tabletop microphone array|
|TCM-1||Plenum network box + one microphone array pendant|
|TCM-1A||Plenum network box with built-in amplifier + one microphone array pendant|
|TCM-1EX||Extension plenum network box + one microphone array pendant|
Each TCM-1 or TCM-1A can host up to two TCM-1EX extension microphones connected in a daisy chain using standard CAT5 or better cable. This means that, with just a single cable run from the ceiling down to the DSP, you can have coverage from three beamtracking microphone arrays, which should be suitable for most small to mid-sized conference room applications.* The TCM-X and TTM-X have a slightly different topology. Each AVB network box supports up to two microphone arrays. So you can use one TCM-X (or TCM-XA) and add a single TCM-XEX expansion microphone array to the same network box. The same applies to the TTM-X and TTM-XEX.
There is a maximum distance of 330' (100 meters) between any network box and the AVB capable network switch. Point-to-point cabling between the TCM-1 / TCM-1A and the first TCM-1EX has a limitation of 33' (10 meters). Point-to-point cabling between the first and second TCM-1EX units also has a limitation of 33' (10 meters). In all models, the supplied pendant microphone allows a maximum drop of 10 feet (3 meters) including any strain relief within the plenum ceiling box. TCM-1 pendants are available in white or black.
The maximum distance between the network box and microphone array for the TCM-X, TCM-XEX, TTM-X, or TTM-XEX is 33' (10 meters). Note that this total distance includes the 6.5' (2 meter) cable provided with the TTM table top microphone array. The TTM cable can be extended a maximum of 26.5' (8 meters) beyond the included cable.
*When installed at a height of 8’ (2.5 meters), the Parlé Beamtracking Microphone maintains a STIPA A rating over a coverage diameter of 16’ (5 meters). Room conditions at time of measurement: RT60 (@5meters) = 425ms, Noise Floor weighted (at the microphone) = 38dBSPL-A.
Each network box receives power over the Ethernet connection. The power requirements of each device are as follows:
|TCM-X||PoE (IEEE 802.3at Class 3, 15.4W)|
|TCM-XA||PoE+ (IEEE 802.3at Class 4, 30W)|
|TCM-XEX||Powered from network box included with TCM-X or TCM-XA|
|TTM-X||PoE (IEEE 802.3at Class 3, 15.4W)|
|TTM-XEX||Powered from network box included with TTM-X|
|TCM-1||PoE (IEEE 802.3at Class 3, 15.4W)|
|TCM-1A||PoE+ (IEEE 802.3at Class 4, 30W)|
|TCM-1EX||Daisy chained from TCM-1 or TCM-1A, power provided by host TCM-1 or TCM-1A|
Network boxes may be directly connected to the AVB port on a Tesira server class device using a PoE+ injector, or via a PoE+ port on an AVB capable network switch.
Beamforming is the ability to shape or steer a microphone array's directivity (or polar) pattern. Consider the situation where you have multiple microphones in a room, or in this case, multiple elements in an array. Sound will arrive at each microphone with a different time delay and level decay.
By utilizing DSP, we can shape the pickup pattern by compensating for the delay and level differences between microphones. A single TCM-1 pendant has eight microphone elements working together to create three 120° zones, each with its own steerable beam. This allows for a full 360° of coverage. A single TCM-X or TTM-X microphone array has 16 microphone elements to create four 90° zones with the same steering ability.
This is all well and good, but beamforming is nothing new, and there are plenty of other microphones out there utilizing this technology. What makes the Parlé series unique is that the microphones use beamtracking technology to analyze the signals from each microphone element in order to determine where the talker is, then passes that information on to the beamforming algorithm to tell it where to steer the polar pattern. This is accomplished, in part, by a process called Voice Activity Tracking.
Voice Activity Tracking
When a signal enters the Parlé microphone array, it diverges into two paths: the audio signal that is sent over AVB to the Tesira server-class device, and a signal used for tracking. The tracking algorithm makes use of aggressive noise cancelation to ensure that noise sources in a room, such as ceiling mounted projectors and HVAC systems, do not cause the tracker to falsely trigger.
Parlé microphone arrays are optimized to only track signals within the frequency domain of human speech,empowering the tracking algorithm to give greaterfocus to focus on talkers in the room. It then passes this information on to the beamformer, which directs its polar pattern to the located talker.
The tracker will follow in both azimuth (left-right) and elevation (up-down) angles and will work independently in each of the available zones.
Adding tracking capabilities to the beamforming microphone array creates a problem for us to solve. If two beams in a single pendant track to the same talker, such as may occur if that person is positioned between two coverage zones, it could introduce comb filtering or other phasing issues. To combat this, we implemented the concept of beam weighting. When two beams are directed toward the same talker, each signal is analyzed and only the stronger signal will be selected to pass through to the remainder of the signal chain.
Beam weighting prevents phasing issues that could occur from two beams tracking to the same signal. However, when the signals are different, such as when two people are talking, it does not stop multiple beams from being used to properly pick up talkers across multiple coverage zones. This processing takes place within the network box.
Beam weighting addresses the issue of a single talker being covered by multiple beams in a single microphone array, but what about a single talker being covered by beams from multiple microphone arrays? For this, we introduced the concept of Intelligent Mixing.
If there are two microphone arrays in a room, they will both track to a human voice source. Intelligent mixing, which occurs post-tracking algorithm, allows the system to identify which pendant has the better signal and deliver that to the final mix. This only applies to a common source. With separate signals in a room, multiple microphone arrays can still be active.
Intelligent Mixing for beamtracking microphones is enabled within the Gating Auto Mixer block when adding it to the Tesira layout file. In the Gating Auto Mixer initialization dialog, select "Preconfigure for Beamtracking Mics." This will optimize the auto mixer settings for use with the Parlé-series microphones. The lower-righthand corner of the Gating Auto Mixer will show "BT" as a visual indication that this option has been chosen.
Biamp's Beamtracking Microphones are ultimately designed with conferencing and collaboration in mind, and you cannot talk about conferencing without mentioning Acoustic Echo Cancellation (AEC). AEC performance is one of the most -- if not the most -- critical processing components in an audio conferencing system. Because Biamp has created both the beamtracking and AEC algorithms within Tesira, both are aware of and communicate with each other to help ensure a quality meeting experience.
When the far end talks, a beamtracking microphone will analyze this signal, identify it as human speech, and want to track to it. However, our AEC algorithm is capable of telling the beamtracker that it is the far end who is talking. This will temporarily lock the beams in place, preventing them from tracking to the far end voice coming out of the room's loudspeakers.
This interaction between our AEC and beamtracking algorithms is patented technology that allows for the requirement of only a single channel of AEC per microphone array. This scenario would typically require three channels of AEC (one for each beam or coverage zone).
Software and programming
Adding Biamp Beamtracking Microphones to a layout is a simple process and resources have been provided to aid in the configuration. Below, we will highlight the blocks that should be included when programming the layout, as well as the options available to optimize settings for use with Parlé microphones.
Parlé I/O Blocks
Parlé microphones are added to the configuration from the I/O Blocks list found under the Audio Object Bar.
Once the appropriate model is selected and added to your layout, an initialization dialog will be shown. This allows you to configure the following:
- Microphone Type (TCM-1, TCM-1A, TCM-X, TCM-XA, or TTM-X)
- Microphone Count (depending on the number of total microphone arrays connected to the network box)**
- Logic Inputs for LED control and muting
- Mute options for multiple microphones as a group, or individually
- Enable logic outputs that could be used to drive logic functions within Tesira based on mic mute state
- Add or remove the amp block when utilizing the TCM-1A or TCM-XA built in amplifier
** TCM-1 and TCM-1A allow a maximum microphone count of 3. TCM-X, TCM-XA, TTM-X allow a maximum microphone count of 2.
After confirming the configuration and selecting OK, the blocks will be added to the layout. For example, choosing a TCM-XA with a microphone count of 2, a TCM-1A with a microphone count of 3, each with an amplifier included, will add the following blocks to the layout:
The Control Dialog for the Parlé Input block will display based on the number of microphones chosen. A software representation of the azimuth tracker will be included for each microphone, as well as mute, level, height settings, and an RMS meter.
When connected live to the system, the azimuth tracker will display an indicator for each beam or coverage zone, and will provide feedback for activity and tracking within that zone. The TCM-X and TTM-X microphone arrays will show a red, green, blue, and yellow indicator to represent the four available beams. The TCM-1 microphone array will show a red, green, and blue indicator to represent the three available beams.
The height should be set at the measured distance from floor to microphone array. This will affect the maximum upward angle at which the microphone will track. A higher setting will limit the angle, keeping the beam from tracking too close to sources coming from the ceiling. A lower setting will increase the coverage angle to accommodate talkers being nearer to the mic's 0° elevation angle.
AEC Processing Block
In most cases, a Parlé microphone input will first be connected to an AEC processing block. The recommended configuration for the AEC processing block when used in conjunction with a Biamp Beamtracking Microphone is as follows:
NLP = Medium
Noise Reduction = Low
AGC = Bypassed
To quickly deploy these settings, a "Preconfigure for Beamtracking Mics" option has been added to the AEC initialization dialog. The most critical of these settings is to ensure that AGC is bypassed. When utilizing beamtracking microphones, we want AGC to occur post-automixer. This AGC processing will be included automatically when adding the Parlé custom processing block to the layout.
Parlé Custom Processing Blocks
In an effort to simplify setup and deployment, Tesira software will install with a series of custom blocks preloaded into the processing library. This will help limit programming time and ensure that recommended steps and settings are being followed when including Parlé microphones in your layout. Each "Parlé Beamtracking Block" will vary by the number of channels, but contain the same processing blocks and a single mixed output.
The EQ is a recommended starting point for each pendant that should be applied outside of any other needed "room" EQ.
The Beamtracking Auto Mixer should look familiar. This is where Intelligent Mixing comes into play. Note the "BT" in the bottom right-hand corner of the block, indicating that "Preconfigure for Beam Tracking Mics" has been selected.
Before mixing the individual microphone array signals down to the single output, we pass through AGC, which has been configured to ensure the best performance and compatibility with Biamp Beamtracking Microphones.
Parlé Amplifier Block
When utilizing the built-in, two-channel amplifier of the TCM-1A or TCM-XA, a two-channel amplifier output block will be added to the layout. This provides controls to set load impedance, level, and mute, as well as monitor the amplifier's current state.
Of particular interest is the Burst indicator. This is a visual indication that Burst power reserves are being utilized to handle peaks in the audio signal.