A sound object (PDF 1.2) is a stream containing sample values that define a sound to be played through the computer's speakers. The Sound entry in a sound annotation or sound action dictionary (see Table 8.32 on page 601 and Table 8.54 on page 625) identifies a sound object representing the sound to be played when the annotation is activated.
Since a sound object is a stream, it can contain any of the standard entries common to all streams, as described in Table 3.4 on page 38. In particular, if it contains an F (file specification) entry, the sound is defined in an external file. This sound file must be self-describing, containing all information needed to render the sound; no additional information need be present in the PDF file.