SONGetSampleInterval

  SONGETSAMPLEINTERVAL returns the sampling interval in microseconds 
  on a waveform data channel in a SON file, i.e. the reciprocal of the
  sampling rate for the channel, together with the time of the first sample

  [INTERVAL{, START}]=SONGETSAMPLEINTERVAL(FID, CHAN)
  FID is the matlab file handle and CHAN is the channel number (1-max)
  The sampling INTERVAL and, if requested START time for the data are
  returned in seconds.

  Note that, as of Version 2.2, the returned times are always in microseconds.
  Uncomment the last line for backwards compatibility

  Malcolm Lidierth 02/02
  Updated 09/06 ML
  Copyright © The Author & King's College London 2002-2006