Technical information

S/PDIF Sony/Philips Digital Interface Format. A widely used digital audio
protocol. It is used as the protocol for all consumer home entertainment
equipment. It is distinguished from the professional AES/EBU protocol by
incorporating the clock timing information in the main signal. Originally designed
for 44.1 and 48 kHz and 16 bits, it now carries up to 96kHz and 24 bits, plus
the bitstreams for the various compressed digital audio standards. The
connections used are generally coaxial or optical.
Speaker Short for loudspeaker.
Speed of propagation Physical waves, whether sound or electromagnetic, have a
typical speed of propagation through various media. This varies depending on the
medium. Light travels through a vacuum at 3x10
8
metres per second. Sound
travels through room-temperature air (20C) at 343.5 metres per second. The
speed varies slightly according to temperature, increasing to 349.3m/s at 30C,
falling to 337.6m/s at 10C.
SPL Sound Pressure Level. A measure of volume or loudness in decibels.
0dBSPL is the quietest that can be heard. A rock concert may produce up to
120dBSPL. The threshold of pain is a little above this. Hearing damage is a
function of loudness and the frequency and period of exposure.
Square wave A signal, the shape of which when displayed is, well, square. In
other words, it holds to a negative value for a time equal to half the wave's period,
then switches abruptly to a positive value which it holds for the same length of
time, then switches back negative again, and so on. How quickly it switches
between these states is determined by how far into the higher frequencies the
equipment in use can extend. Square waves rarely form part of music, and are
primarily used as diagnostic tools, since inspection of how well equipment handles
a square wave can reveal a lot about its high frequency handling and whether it
shifts phase across its frequency handling range.
Stereo or Stereophonic. In the home, an audio system which delivers two
channels of music, left and right, to create the illusion of a plane of sound facing
the listener. High quality audio systems will make the sound stage actually wider
than this space, and provide sensations of both vertical sound placement and
depth in the stage, offering a ‘holographic’ or multi-dimensional audio effect.
Contrast with mono and surround sound.
Streaming (multimedia) is data that is constantly received by, and normally
presented to an end-user while it is being delivered by a streaming provider. In a
general sense, includes all audio or video playback. The name refers to the
delivery method of the medium rather than to the medium itself. The term is