Mumble

Mumble is an open source application used for real time voice communications, usually for gaming. It is optimised for low latency voice transmissions and has exceptional quality even at low bitrates. This makes it well suited for live broadcasts of conferences, interviews and other situations where speech intelligibility is important. You can read more about mumble here on Wikipedia.

Mumble for Broadcasts
This only covers configuration for listening into broadcasts. If you wish to use Mumble otherwise, many general setup tutorials are available on the Internet which will guide you through the process of calibrating and configuring your input devices.

Downloading Mumble
Mumble is available free of charge from Sourceforge at http://mumble.sourceforge.net/. As of the time of writing, there are builds available for Windows, Mac OS X, Linux and iOS. Most Linux distributions have mumble in their official repositories.

Installation
The screenshots shown here are for a fresh installation on Windows 7, though the interface should be similar for Mac OS X. Run the executable after download (Windows) or download and open the disk image then drag and drop the Mumble application to your Applications folder (Mac) and follow the prompts.

By default, only the client is installed. You can uncheck Mumble (backward compatible) as it is not required in most circumstances. Murmur is not needed unless you wish to set up your own server.

Configuration
After installation has finished, open Mumble. If this is the first time running Mumble, the Audio Tuning Wizard will open.

Click cancel to close the window, and cancel again to dismiss the Certificate Management wizard.

You should now be presented with a window to choose which server to connect to. (If this does not automatically appear, go to Server > Connect). Click on Add New and enter the address of the server you wish to connect to. The port can usually be left on the default setting (64738). Pick a user name and assign a label to the server to help you identify it. Click OK to save the settings.

The server you added should now appear under the 'Favorite' list. Highlight it and click connect to join the audio stream.

Your window should look something like this if you have connected successfully. Be sure to click the microphone icon (between information and headphones) to mute yourself. Listeners in the stream appear in the right hand panel of the screen. You can send and view messages to others in the left hand pane similar to traditional instant messaging.

Recommended Configuration Options
The following additional configuration settings are recommended to make using Mumble better for all parties. When you have finished making any configuration changes click "Apply" and then "OK" to save them.

Push-To-Talk
The Push-to-Talk feature allows specifying a key to activate the microphone. This means you transmit the sound you wish to transmit (i.e. when you're talking) and not incidental background noise, such as typing or other background noises.

To set Push-to-Talk go into the Mumble settings and in the Audio Input section look for Transmission. There should be a pull down menu with "Continuous", "Voice Activity" and "Push To Talk"; select the last one.

Then go into the Shortcuts section and click Add. There should be a new shortcut called "Unassigned" in the Function column. Click on it where it says "Unassigned" and you will see it becomes a pull down menu, select "Push-to-Talk" there. Click in the Shortcut field to the right and press the button you want to use to activate the microphone.

It is recommended you specify a key they you generally don't use when typing a lot. Ideally you want a key that is not frequently used while typing since you may be on IRC or typing something else at the same time that you are using Mumble.

No Loopback
Disabling audio loopback prevents your own words being echoed to you as you say them, which can be quite distracting. This is usually disabled by default, but may not be.

In the Mumble settings go to the Audio Output section. Down the bottom is a Loopback Test area with a pulldown menu. This should be set to "None" instead of "Local" or "Server".

Headphones
Headphones should be used to prevent other people's words being played back through your microphone and creating an echo effect of everything said while your microphone is live. On most PCs and laptops this does not require a headset with a microphone since there are usually separate jacks for audio input and audio output.

In the Mumble settings go to the Audio Output section. In the Positional Audio section (above the Loopback Test section) is a tickbox for using headphones. Tick that box and plug headphones into the audio output jack on your computer.

Disable Text-To-Speech
Text-To-Speech uses a synthesised voice to read content typed or pasted into the text chat box in Mumble. This frequently interferes with the audio you want to hear: the other speakers.

In the Mumble settings go to the Messages section. Scroll down the bottom and remove the tick from "Text Message" in the "Text-To-Speech" column. You may want to remove ticks from some of the other fields too.