1.9. Interactive sound design case study
Interactive CD-ROM is the
closest medium that web audio
developers can look to for guidance on creating sophisticated
soundtracks. The basic principles for interactive CD-ROM design can
be directly applied to the Web. Both mediums share similar technical
limitations, bandwidth challenges, and logistical concerns.
There is much to learn by examining the mistakes and innovations made
by those who pioneered interactive sound design in the
CD-ROM medium. Here are some approaches
to common problems.
1.9.1. Selecting sounds
Emphasizing lower frequencies over higher-pitched sounds greatly
improves audio playback quality over the Web. If you know you are
going to lose a lot of high-end frequencies through extreme
compression for example, then avoid using high-pitched sounds at the
Most high frequency
above 5,000 Hz and 10,000 Hz, such as whistles and shattering glass
are lost when sampling down to 8-bit or when using extreme
compression algorithms. For example, buzzing flies in
ambiance will lose its characteristic sound when reduced to 8-bit and
will become random, indistinguishable noise. An effective strategy
would be to add the lower frequency sound of owl hoots to your forest
mix instead of high-frequency buzzing flies.
1.9.2. Timing loops
In late 1994,
co-author Josh Beggs and audio engineer
embarked on an eight-month soundtrack production for EMI Records. The
project was to create a CD-ROM for the multiplatinum band
Queensrÿche called the "The Promised Land" -- an
interactive rock-and-roll adventure game (see Figure 1-23) containing a separate fantasy world for each
of the five band members. Each band member developed a unique theme,
environment, and palette of sounds for his fantasy world. But due to
technical constraints and limitations in CD-ROM storage capacity, the
soundtrack had to be limited to an 8-bit, 22,050 Hz mono channel of
Figure 1-23. The Queensrÿche Promised Land CD-ROM interactive
As sound designers, the task was to create a rich and compelling
interactive soundtrack despite the limited bandwidth and resources.
Designing for an uncontrollable sequence of events was a recurring
challenge. We discovered two ways to conquer this challenge:
Use repeating sound loops instead of a
"play once" sound
file. One of
the greatest challenges of integrating sound into the interactive
medium is the inability to determine the length of time people will
spend on any given page or screen. In the beginning of the
Queensrÿche project, we set about
creating the appropriate soundscapes for each of the five fantasy
worlds that comprised the Promised Land disk. In the initial
development phase of the sound design project, we created 35-second
sound files to play across three or four screens. Each sound had
fade-ins and fade-outs for smooth transitions from one audio file to
the next, as shown in Figure 1-24.
This approach was based on sound design techniques developed for
linear media with predictable timelines such as film and television,
but it proved to be inadequate for interactive media. If the user
stayed on one screen or failed to pass through the next three screens
before the sound ended, the audio would fade to silence, disrupting
the ambience and realism the soundtrack was supposed to reinforce.
Like many other pioneering interactive sound designers, we started to
use loops or sound clips that seamlessly repeated infinitely to build
a soundtrack that worked in an interactive environment. (Earlier in
this chapter, we explored how to build good loops.)
Figure 1-24. A 35-second ambient sound with fade-ins and fade-outs
Practicing good audio etiquette: multimedia rules of the road
Building a site with audio and animation can be a risky endeavor. If
you implement full-scale audio, someone is likely to get an error
message. Most of the time it will have nothing to do with your code.
Often error messages appear because of a browser configuration
mistake or a client-side anomaly beyond your control.
The following steps can help minimize the negative impact of audio:
Inform your clients that using audio is a risk factor. Explain the
drawbacks and benefits of a web soundtrack. Use audio with caution on
web sites visited frequently for key information or used in the
office during work hours. More conservative news and commerce sites
should, at a minimum, incorporate button sounds for easier navigation
and informative narration. Full-scale multimedia works best for
entertainment and promotional web sites.
If you are going to build a web site with a multimedia format such as
Flash, Shockwave, or RealMedia, start with a home page that displays
most of the important text and graphics in standard HTML format. For
an example of this style, visit the Raspberry Media web site at
http://www.raspberrymultimedia.com. If you
construct most of the home page layout in HTML with your multimedia
content playing in a smaller dedicated media window, you can avoid
the undesirable situation of losing visitors who do not have the
right plug-in or browser to view the home page. Embedding a smaller
media window in your pages also reduces the file sizes of your
animations and provides a sense of movement on the home page, as seen
on the Raspberry Media web site.
When possible, avoid music loops that repeat indefinitely. Make your
loops fade out or stop after a reasonable number of cycles. Some
sites tastefully include a "stop music" button on every
web page that has an audio loop.
Smooth the transitions between
screens. Smooth transitions are critical to good
interactive sound design. In our initial approach, when the user
moved from one screen to the next, the previous sound file ended
abruptly, cutting to silence or to the next sound loop at full
volume. Such abrupt transitions detracted from the effectiveness of
the soundtrack. Remember that the idea was to create an ambient
"soundscape" that made the user feel as if he or she were
walking through that particular fantasy world environment. You may
have encountered crude audio drop-outs on many web sites, where the
sound abruptly stops when you click to another screen. It is not a
To create smooth transitions between screens, we added
"mouse-on" fade-out scripting controls.
When the user clicked to move to the
next scene, each sound loop would fade in, rising in volume over a
period of a few seconds.
After creating a collection of loops for each world of the Promised
Land, we embarked on the overall issue of where to distribute the
loops. The interactive pathways or architecture of a CD-ROM look much
like a web site. Both mediums generally consist of clusters or groups
of screens linked to a start or index page that in turn is linked to
another index page, as shown in Figure 1-25.
The challenge was to find a balance between diversity and
consistency. We wanted to use several different sound files for each
environment so that the sound experience for the user would change in
different settings. We did not want one sound file to loop for
several minutes or to play for only a few seconds. The goal was to
distribute the audio loops evenly across one of the page groups or
clusters, as illustrated in
Figure 1-25. A site architecture diagram of a web site or CD-ROM with pages clustered around a start or index page. In the Queensrÿche CD-ROM, audio clips were programmed to play across all pages in a cluster.
The different cluster of pages in Figure 1-25
approximate a scene or landscape within the Queensrÿche CD-ROM.
The index page represents the start point where visitors begin their
journey on a pathway that leads in several directions, one into a
dark forest, another down to an ocean lagoon, and two more that lead
to secret doorways hidden in the nearby forest. Each cluster in the
illustration represents the pages or screens associated with each
The most effective technique was to assign one sound loop to each
group or cluster of pages. By scripting a sound file to play over
several screens, we avoided the sound drop-outs associated with
attaching an individual sound clip to each screen. The overall
soundtrack was more effective in creating a mood or ambience when the
sound was consistent or present as someone clicked through the
multiple screens of a group.
The technique used for the Queensrÿche CD-ROM can be used in a
web site built with frames. By placing the pages of a site within
several frame sets, you can assign a looping audio file to play
across several pages. For example, you could place five audio loops
across a 30-page site by creating five unique frame sets with six
pages each. One loop would play across all six pages within the frame
set. If you build a Flash- or Shockwave-based web site using
Shockwave's powerful Lingo script or Flash's limited set
of command scripts, you will have even more control over how sound
loops play back across pages.
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