This chapter focuses on creating and editing sound and music for the course Music for everyday life. This involves finding free audio online, creating our own voice recordings, remixing audio, podcasting, and even converting text to speech.
By the end of this chapter you will be able to do the following:
- Finding free music and sounds online for your multimedia projects
- Selecting appropriate audio formats and settings according to your needs
- Using a set of free software tools for common procedures in sound and music editing
- Extracting audio from CDs
- Creating voice recordings
- Integrating all of these into Moodle
As with pictures, the usual suspect for finding free audio tracks online is again Wikimedia Commons. This is a huge database of multimedia elements, and we can find interesting stuff there. But before we look into these, let's start with the basics of audio formats so that we can pick better files for our courses.
In our everyday life, we can find music and sound in several formats. The most common of these formats are:
- PCM: This is the standard format used in CDs. It is an uncompressed audio format, which implies large file sizes—around 10 MB per minute.
- WAV: WAV is usually used to store the PCM file format. It can contain audio in several rates and bitrates (these are concepts that we will see in a moment).
- MP3: MPEG Layer 3 is one of the most common audio formats on the Web. It is also the name of the codec that reduces original audio files sizes (for example, depending on the bitrate and rate, a CD track can be reduced to 1/10th the size of the original file size).
- WMA: Windows Media Audio is the standard audio format released by Microsoft.
- OGG: OCG is an open source file format that can contain several codecs, Vorbis being the most common.
- MIDI: The MIDI format is an industry standard for electronic music, allowing electronic musical instruments, computer software, and other equipments to communicate. For example, a MIDI keyboard uses MIDI to communicate with a computer. You have probably heard a MIDI file before, usually a very small sized file, which sounds like electronic music from the 80s (yes, they were used quite a lot in those weird times). However, as MIDI files don't actually have audio waveforms in them, it is possible to associate real instrument sounds to MIDI instructions and have nice sounding files.
There are four concepts to keep in mind while dealing with audio files (and video files, as we will see in the next chapter), namely file format, codec , rate , and bitrate.
The file format is the easy one—whatever extension a file has, that is its file format, for example, MP3, WAV, and OGG. The codec does the processing of the data inside the file; so for example, in OGG, it can use the Vorbis audio codec.
In addition to these two, rate and bitrate refer to the number of times per second that an original audio is sampled and stored in Hz, the same as 1/second, and the number of bits that are processed in every unit of time (Kb/s) respectively.
I would recommend MP3 as a working format for our daily needs (in Moodle or anywhere else), in which we can use different rates and bitrates according to our goal; for example, make a song excerpt from a CD available or add voice to forums. Check the following table for some reference values that will be useful later on:
|
Rate |
Bitrate |
When to use |
|---|---|---|
|
44,100 Hz |
128 Kb/s |
To rip CDs and use in most cases |
|
11,025 Hz |
48 Kb/s |
To record voice for a daily use (interviews, students answers, comments, and so on) |
Now that we know this, let's start by finding free sound tracks and free music on the Web for our audio projects.
The Internet Archive (http://www.archive.org) is an online library that provides permanent access to historical material on the Web, a kind of "memory" of the Web. We can see this in action, for example, in the Wayback Machine (http://www.archive.org/web/web.php), where we have access to static versions of web pages from their start to the present day, with some of the archiving starting as far as 1996 (this can be a really fun activity!). One of the subprojects of this initiative is the Audio Archive (http://www.archive.org/details/audio), a library with over one million free digital recordings, ranging from old radio shows to concerts and poetry readings.
We can either search this collection using the search form or explore the subcollections.
Freesound (http://www.freesound.org) is a collaborative collection of sounds licensed under a Creative Commons license, allowing us to use them in our own works.
CCMixter (http://ccmixter.org) is a project from the Creative Commons initiative, where we can find lots of samples to use in our audio projects. We can also upload the results to the same site. All of the content is licensed under Creative Commons licenses.
In addition to the services that we saw earlier, we can also find music and sounds for free at the following links:
- Musopen (http://www.musopen.com) – an online music library of public domain music
- Soundbible (http://soundbible.com) – an online library of free sound effects and sound clips
Before we get into the details of how to create audio for our course, let's have a quick look at how we can integrate audio into Moodle. We could start by downloading an audio file from the WIRED CD http://creativecommons.org/wired and then Moodle it!