Choosing Audio Formats for the Web


Audio is a popular digital media content type on the Web. Although the most popular use of audio seems to be for publishing music in the form of song samples and whole songs, audio is also used to provide audio greetings, web page narratives, and soundbites from speeches. 

 The three de facto audio file formats used for publishing audio on the Web in decreasing order of popularity are:


While the ideal situation would be to be able to publish CD quality sound on the Web, the reality is that most connections to the Web are too slow to be able to download high quality audio in a reasonable amount of time let alone play high quality audio in real-time (i.e. playing audio live). For instance, just one second of CD quality stereo audio with no compression requires 172.3KB (1KB = 1024 bytes): 
      bytes           samples     channels      bytes            bytes
    # ------ = 44,100 ------- * 2 -------- * 2 ------- = 176,400 ------
      second          second       sample      channel           second
A client using PPP over a 9600bps modem transfers data at the rate of between 550 to 750 bytes per second depending on the data transfered as well as line conditions. At this rate 1 second of CD quality stereo audio will take between 4 to 5 minutes to download! 1 minute of CD quality stereo audio would require 10MB and would take between 4 and 5 hours to download!

So, to be kind and to keep the interest of the users who will download your audio files, you must compromise audio quality and content length to minimize download time. The following table suggests audio settings for different types of audio content and indicates uncompressed space and download requirements: 

                          Bits/Bytes   Sampling  Bytes per  9600bps
Content         Channels  per Channel  Rate      Second     Download
--------------  --------  -----------  --------  ---------  --------
Speech              1       8 / 1         8KHz    8,000Bps   15 sec
Monaural Music      1       8 / 1        16KHz   16,000Bps   29 sec
Stereo Music        2       8 / 1        16KHz   32,000Bps   58 sec