Digital Sound

Digital Music

Overview Portable CD players are no longer the cool way to enjoy music on the go. When digital audio players arrived in 1999, music lovers first embraced MP3 players, then migrated to iPods and smartphones. The world of digital music players includes digital codecs like MP3, WMA, and AAC, music distribution Web sites, software for converting audio CD tracks into digital format, and portable music players.

Audio codecs In 1987, a German company called Fraunhofer developed the MP3 (MPEG Audio Layer 3) standard for encoding and compressing music into digital files about one-tenth their original size. These small files were not quite up to the quality of the originals, but they offered convenience—files could be easily transferred over the Internet and many files could fit on a typical computer hard disk. At this page, you can find a brief history of MP3 development and tables that compare sound quality using various compression techniques.

Fraunhofer also developed AAC (MPEG-2 Advanced Audio Coding) used by the Apple iPod. You can find technical details about AAC at the Fraunhofer Web site For a less technical discussion, check out the Wikipedia AAC page.

Microsoft developed the WMA (windows media audio) codec and incorporated it in the Windows operating system as the Windows Media Player. You can read details and find comparison charts with other audio codecs at

MP3, AAC, and WMA are proprietary codecs, which poses issues about licensing. An open source and free audio codec called Ogg Vorbis has been available since 1999, but has not yet become popular as an alternative to AAC and MP3. You can get up to listen so some audio samples of Ogg Vorbis files at

Online music stores Lots of MP3 and AAC music is available on the Internet. The idea of downloading digital music was first popularized by a file sharing network called Napster, which was sued by the recording industry for illegally distributing copyrighted music. You can find out how Napster worked at

File sharing technology itself is not illegal, and it has many potential legal uses. File sharing networks are explained at and File swapping sites still offer digital music downloads. You can find them by entering “music download” in any search engine. Before you download, make sure the music is offered legally by checking the site’s policies.

Today, many commercial Web sites offer music downloads in a simple client/server architecture. These sites are often referred to as online music stores and typically charge a small fee for each download or require a monthly subscription for access. Before downloading music from one of these sites, you might have to download a player designed to work with MP3, AAC, WMA, or other music format. A few of the most popular online music stores include:

·MSN Music (

·Apple iTunes (

·Walmart Music Downloads (

· MP3 (

·Rhapsody ( )

·CD Universe (

Ripping audio CDs In addition to obtaining music from file sharing networks and online music stores, you can convert the tracks on your audio CDs to digital format. To rip a CD, you’ll need CD ripper software. Most digital music player software utilities, such as Windows Media Player and iTunes include the software necessary to rip audio CDs.

Once this software is installed, follow the directions. In general, ripping consists of the following steps:

·Start your CD ripper software

·Insert the CD containing original music

·Select the track(s) you want to rip

·Select a format, such as MP3, AAC, WMA, or WAV, for the ripped files

·Select the destination for the ripped files

·Initiate the conversion process

If you want to get into the details of ripping, you can read all about it at

Digital music players Music in MP3, AAC, WMA, or other digital formats can be easily stored on a computer’s hard disk, copied to CDs or DVDs, or transferred to portable devices called digital music players. The iPod has emerged as one of the most popular portable music players, but many other brands are price and feature competitive. Because new models appear so frequently, it is difficult to provide an up-to-date list.  Before you buy one, be sure to read the PC Magazine article “Digital Audio Players: The Essential Buying Guideand “MP3 & Digital Music Players: Top 10 Buying Tips”  You can also use the MP3 Player Buying Guide to find the player that’s best for you.

Digital Speech Synthesis & Recognition

Overview Those of you who are familiar with the popular science fiction TV series “Star Trek” have already been introduced to the basic concepts of speech synthesis and voice recognition. On that TV series, characters spoke to the central computer and the computer spoke back. Today, however, most voice recognition software can only take dictation. It cannot comprehend words or their meaning. The ability to speak into a microphone and have your PC generate accurate text or recognize voice commands is the goal of current voice recognition software. Speech synthesis is the creation of speech from text through the use of your PC. Many new developments in digital speech technology, such as universal translators and truly dynamic voice recognition software, may be just on the horizon.

General Information Speech synthesis and voice recognition are both relatively new digital sound technologies. Until recently, digital speech tools were prohibitively expensive. Communications services have used this technology for directory services as well as e-mail and voice mail systems. Affordable speech synthesis and recognition tools are now available to anyone with a PC and a microphone. What is the difference between speech recognition and speech synthesis? Visit the site to read their definitions of “voice recognitionand “speech synthesis. Links to additional digital sound information can also found on these pages. Another good source of information about digital speech is the Speech and Sound Links page. Here you can find links to sites that deal with speech synthesis and recognition, sound analysis, and digital audio formats. An extensive list of FAQs is available at Digital speech software tools, complete with descriptions and links to the manufacturers’ home pages, are available for download at

Speech Synthesis Resources Synthesized voice of the past sounded mechanical and unnatural. Today, speech synthesis sounds more natural, due to the wide choice of voice types, cadence, and accents. Speech synthesis information, including more than 500 links, is available at Links to speech synthesis and recognition resources can be found on this Speech Web Sites page. Speech synthesis utilities can be downloaded from this Web page. You’ll find both shareware and freeware programs included there. ModelTalker synthesizer, a modern speech synthesis program developed by the Speech Research Lab, is available for download at Samples of synthesized speech generated by ModelTalker are available on this page as well. These synthesized speech samples will provide you with examples of the different features to be considered when using speech synthesis software.

Speech Recognition Resources Speech recognition software was first developed for PCs to perform tasks that include word processing and the execution of simple commands. Early versions of these programs were clumsy and unreliable. With each update in this type of software, there is an improvement in the accuracy of dictation. Newer software programs have more leeway for different accents, speeds, and voices. To browse resources, including FAQs, links, job postings, and discussion forums, visit the Commercial Speech Recognition page at Another broad-ranging resource is the Yahoo! Voice Recognition page. Here you can find links to software, articles, and tutorials. Speech recognition forums for both PC and Mac users can be accessed at this page. If you are looking for software that can add voice recognition capabilities to your word processor, then visit or

Additional Links What is the future of speech synthesis and voice recognition technology? Visit to learn about a universal language translator that is being developed. Additionally, you can read about and listen to AT&TLabs’ speech synthesis software “Natural Voices--some of the most naturally sounding synthetic speech.