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EchoDamp
Using the ECHODamp Software

Table of Contents
Using ECHODamp to Mix the Audio in a Videoteleconference (VTC)
The Mixer window in ECHODamp operates much like any standard audio mixer. Users will find the usual complement of controls including Volume faders, Pan knobs, Mute and Solo buttons, as well as LED meters. As with all software-based mixers, the input levels to the Mixer are adjusted with the trim controls on your hardware audio interface (please see the manual that came with your audio interface for instructions on adjusting input trim levels). In addition to these standard mixing controls, ECHODamp contains a number of additional tools for controlling echo in a VTC. These echo control tools are explained in detail in the section entitled Using ECHODamp to Control Echo in a VTC.

EchoDamp Main Mixer
Hi Pass Filter
Hi Pass Filter Window
Monitor Controls Window
Monitor Controls Window


Using ECHODamp to Control Echo in a VTC
Due to the wide dynamic range and frequency content of music, there is no "magic bullet" for echo control in a musical VTC. Echo control consists of three essential stages, with the first being Physical Echo Control. In order for any echo control system to be truly effective you must first take steps to configure the physical space and audio equipment for optimal echo rejection. Once you have done that, the specialized tools in ECHODamp allow you to easily and intuitively accomplish the remaining two stages: controlling outgoing echo (the remote site hears their echo) and controlling incoming echo (you hear your own echo). Echo control is a collaborative process between the two sites. Although ECHODamp is designed to control echo in both directions, for best results, both sites in the VTC should follow these steps rather than attempting to control all the echo from just one location. Due to the way echo control works in ECHODamp, you should deal with the outgoing echo (and have the other site do the same) before working on the incoming echo. You may, in fact, discover that after controlling the outgoing echo from both sites you don't even have incoming echo. If there is still a bit of incoming echo, then proceed to dealing with it as describe in the controlling incoming echo section, but control the outgoing echo first.

Using the Downward Expander to Control Outgoing Echo
The purpose of the Downward Expander is to prevent remote site audio from entering the microphones at the local site. The Downward Expander listens to the incoming audio on its channel and determines if that audio is above a predetermined loudness level or not. If you have performed the Physical Echo Control steps, then audio coming from the remote site through the loudspeakers will approach the microphones from their "null" spot and enter the microphone channels at a considerably quieter level than the audio coming from the local performers. The Expander allows you to set a Threshold level so that remote site audio is below that level, and the local audio is above the level. Thus, the Threshold tells the Expander whether the audio entering the microphone is from the local site or coming from the remote site through the loudspeakers.

When the Expander determines that the incoming audio (Program Input) is above the Threshold, it fully opens the audio channel so that the Program Output is at the same level as the Program Input. However, if the incoming audio drops below the Threshold, the Expander reduces the level of the Program Output, thus preventing the remote site's audio from being transmitted back to them. Once the Threshold level is determined, the other controls allow you to fine-tune the performance of the Expander to get the most effective and transparent response.

Note: Downward Expanders should only be used on microphone channels. Since line level devices such as CD players and synthesizers cannot "hear" audio from the loudspeakers, the Expander should be bypassed for these channels. If you are running your microphones through a hardware audio mixer and connecting the outputs of that mixer to ECHODamp, you should engage the Expander on the channels to which the mixer is connected.

Step-By-Step Instructions for the Downward Expander

  1. Perform the Physical Echo Control steps first.
  2. Open the Downward Expander for a particular microphone channel by clicking the EXPANDER button near the top of that microphone's input channel strip.
  3. Have the local performers sing or play some of their repertoire while you watch the level on the Program Input meter. It's important to have them actually perform the kind of music they will be doing in the VTC so that you get accurate readings. You will want them to sing or play quiet passages, as well as loud ones, so you can ascertain the entire dynamic range they will use.
  4. Turn the ATTACK THRESHOLD knob (or drag the green Threshold indicator) to a point where the audio level from the local performers rises above the green Threshold indicator as soon as they make a sound.
  5. Turn the RELEASE THRESHOLD knob (or drag the red Threshold indicator) to a point where the audio level from the local performers remains consistently above the red Threshold indicator until they stop making sound.
  6. Have the remote performers sing or play some of their repertoire and make sure that the audio level from the remote site remains consistently below the green Threshold indicator. Again, have the remote site do both quiet and loud passages for comparison. Note: You may need to go back and forth a couple of times between the local and remote performers to find the right Threshold settings. Once you have the two Thresholds set:
  7. Adjust the RATIO knob to determine how much the Program Output is reduced when the audio drops below the Release Threshold. Turning the RATIO knob to the right causes a greater Gain Reduction, while turning the knob to the left causes less Gain Reduction. You will probably find that settings between 1:4 and 1:10 work best.
  8. The following controls can be used to fine-tune the performance of the Downward Expander as well as to save and recall presets.
    • The ATTACK knob determines how quickly the Gain Reduction stops when the audio level rises above the Threshold. To avoid cutting off the beginnings of sounds, you will usually want this to be as fast as possible. Thus, a setting of 0.1ms to 1ms will be typical.
    • The HOLD knob adjusts how long the Expander waits once the audio level has dropped below the Release Threshold before reducing the gain on the channel. Longer settings will allow for slow decays of instruments, but may start allowing some echo to enter the system
    • The RELEASE knob adjusts how quickly the Gain Reduction begins once the incoming audio has remained below the Release Threshold for the duration of the Hold time. To allow for a natural-sounding decay, you will find that settings between 100ms and 500ms usually work best.
    • The INPUT and OUTPUT knobs adjust the Program Input and Program Output levels respectively by +/-10dB. For most situations you can leave them at their default setting of 0dB.
    •The BYPASS button allows you to turn off the Expander and let the audio pass through unaffected. When the button is illuminated, the Expander is bypassed and not processing audio.
    • The PRESET button opens the Preset window for the Downward Expander, allowing you to load, edit, save, create, and delete presets for the Expander modules. The Expanders all share the same presets, so if you make changes to a preset in one Expander, those preset changes will be available to all the Expanders.
For more information on the Expander, or any of its functions, please see the Downward Expander section of this manual.

Expander Up   Expander Down
When the Program Input level rises above the
Attack Threshold and remains above the Release Threshold,
the Program Output is unaffected.		   When the Program Input drops below the
Release Threshold for the duration of the Hold time,
the Program Output is reduced.



Using the 2-Channel Ducker to Control Incoming Echo
The purpose of the 2-Channel Ducker is to reduce the amount of your own audio returning to you as echo. If the remote site is properly configured and using the Downward Expander in ECHODamp on their microphones, you may not even need the DUCKER, or only need a very small amount of it. The 2-Channel Ducker can also be the "last resort" tool if the remote site is unable to control echo at their end.

The 2-Channel Ducker listens to your local microphones and turns down the audio coming from the remote site whenever you are singing or playing. It uses the Sidechain Delay function to wait until the round-trip latency time has passed before turning the remote audio down. Thus, the remote audio is lowered just as the echo of your sound is about to come out of your loudspeakers.

When the Ducker determines that the incoming audio from your microphones (Sidechain Input) is above the Threshold—the local performers are singing or playing—it reduces the level of the remote site audio to the loudspeakers (Program Output). However, if the incoming audio from your microphones is below the Threshold—the local performers are not singing or playing—the Ducker allows the Program Output to pass at full volume. Like the Downward Expander, you begin by determining the Threshold level. Once the Threshold level for the Sidechain Input is determined, the other controls allow you to fine-tune the performance of the Ducker to get the most effective and transparent response.

Step-By-Step Instructions for the 2-Channel Ducker

  1. Perform the Physical Echo Control steps first. Determine if the remote site is using ECHODamp and its Downward Expander. If they are, you may not need the Ducker, or only need to use it very lightly.
  2. Run the Latency Detector to determine the round-trip latency of your VTC.
  3. Ensure that the Sidechain Delay in the main Mixer is not bypassed (BYPASS button is not illuminated).
  4. Press the SIDECHAIN buttons (the buttons will illuminate) on the inputs of the microphones you are using. This sends a copy of their signals to the Sidechain Input of the 2-Channel Ducker.
  5. Open the 2-Channel Ducker by clicking the DUCKER button located beneath the AUDIO ON/OFF button in the upper-left of the main Mixer window.
  6. Have the local performers sing or play some of their repertoire while you watch the Sidechain Input meter in the Ducker. It is important to have them actually perform the kind of music they will be doing in the VTC so that you get accurate readings. You will want them to sing or play quiet passages, as well as loud ones, so you can ascertain the entire dynamic range they will use.
  7. Turn the THRESHOLD knob (or drag the Threshold indicators) to a point where the audio level from the local performers is consistently above the Threshold indicators. Once you have the Threshold set:
  8. Adjust the REDUCTION knob to determine how much the Program Output is reduced when the Sidechain Input is above the Threshold. Turning the REDUCTION knob to the right causes a greater Gain Reduction, while turning the knob to the left causes less Gain Reduction. You will probably find that settings between 10dB and 30dB work best.
  9. The following controls can be used to fine-tune the performance of the 2-Channel Ducker as well as to save and recall presets.
    • The ATTACK knob determines how quickly the Gain Reduction begins when the Sidechain Input level rises above the Threshold. A setting in the range of 10ms to 50ms will generally provide the smoothest response.
    • The RELEASE knob adjusts how quickly the Gain Reduction stops once the Sidechain Input level has dropped below the Threshold. To allow for a natural-sounding release, you will find that settings between 50ms and 200ms usually work best.
    • The INPUT and OUTPUT knobs adjust the Program Input and Program Output levels respectively by +/-10dB. For most situations you can leave them at their default setting of 0dB.
    • The BYPASS button allows you to turn off the 2-Channel Ducker and let the audio pass through unaffected. When the button is illuminated, the Ducker is bypassed and not processing audio.
    • The PRESET button opens the Preset window for the 2-Channel Ducker, allowing you to load, edit, save, create, and delete presets for the Ducker.
For more information on the Ducker, or any of its functions, please see the 2-Channel Ducker section of this manual.

Ducker not reducing output   Ducker reducing output
When the Sidechain audio level is below the Threshold,there
is no reduction in the Program Output level to the loudspeakers.		   When the Sidechain audio level goes above the Threshold,
the Program Output level to the loudspeakers is reduced.



Keyboard and Mouse Shortcuts in ECHODamp

Suggestions for Improving Performance in ECHODamp
Like most full-featured computer audio programs, ECHODamp can put a substantial load on your computer's CPU. To reduce that load and improve performance—especially on slower computers—follow these two suggestions:

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