Sampling Basics - ESI ESI2000 Operation Manual

Sampling
Basics
10
ESI Operation Manual
Percussive Voice
DIGITAL SAMPLING The signal is repeatedly measured at a high rate and the measurements are
stored in digital memory. Upon playback, the measurements are converted back into voltages to
reconstruct the original waveform.
Throughout this manual we will use the terms and concepts described
and defined below. Read through this section carefully, even if you don't
retain it all. You can refer back periodically as you read through the
manual until you understand the basics and definitions.
The ESI is conceptually like a tape recorder. However, the recording
process is very different since the ESI digitally records into its computer
memory. Sounds for the ESI can be loaded via removable-media hard
disk, magneto-optical disk, CD-ROM using the SCSI interface; or
through the S/PDIF Digital interface; or even through the MIDI interface
using MIDI Sample Dump.
Computers can accept information only in the form of numbers, so the
ESI accepts audio signals coded into binary numbers. Samplers work by
examining (sampling) the incoming signal level at a very high rate
(44,100 times a second for compact discs), and sequentially recording
these different levels in memory. Once stored, these samples may be
played back (in the proper sequence, of course) to reconstruct the
original signal. For instance, if a two-second sound was being sampled at
44.1 kHz, it would require (2 X 44,100) or 88,200 samples to be
recorded. As you might imagine, shorter sounds require fewer samples.
A sound can be manipulated once it has been recorded. Playing back the
samples in reverse order from which they were stored plays the sound
backwards. Playing back the samples at a faster rate than the rate at
which they were stored raises the pitch. Playing back at a slower rate
lowers the pitch, much like a tape recorder' s variable speed control.
1 second
Each vertical line
represents a sample.
Each sample takes
a "snapshot" of the
instantaneous signal level.