card at any other time, use the sound preferences graphical tool by searching
the Dash for “sound.”
In addition, Ubuntu uses an additional layer of software called PulseAudio.
PulseAudio, which is a sound server, acts as a mediator between the various
multimedia programs that have sound output and the ALSA kernel drivers.
Over the years, many different sound servers have been used in Linux, each
with different strengths, usability issues, and levels of documentation. These
various sound servers have often been forced to run side-by-side on the same
computer, causing all sorts of confusion and issues. PulseAudio aims to
replace all of them and work as a single handler to accept output from
applications that use the APIs for any of the major sound servers already in
use, such as ESD, OSS, GStreamer, and aRts, and route the various output
streams together through one handler. This provides several advantages,
including the ability to control the output volume of various programs
individually.
PulseAudio has matured over the past several releases and is better and more
powerful than ever before. Although there were stability issues and
complaints early on, they don’t seem to be problematic anymore except in
unusual hardware combinations and special cases, and more and more
features have been implemented. For more information about PulseAudio, see
http://www.pulseaudio.org.
Adjusting Volume
Ubuntu offers a handy utility that you can use to control the volumes for
various outputs from your computer. For a simple master volume control, just
click the speaker icon in the top-right corner of the screen and move the slider
left or right.
Alternatively, you can control all the sound settings for the system to make
sure you have set everything to your taste, as shown in Figure 6.1. To access
the volume control, click the speaker icon and select Settings and then select
Sound from the Settings options in the list.