Operating instructions

D-2
enable the soundtrack to carry louder sounds with lower distortion and fewer
signal losses. The result is a dramatic improvement in soundtrack dynamic
range, that is, the volume range between residual film grain noise and the
loudest sounds that can be recorded accurately.
Recording
or
Transmission
−
+
Noise
Σ
Σ
+
+
Band 4
9 kHz
High Pass Filter
Band 3
3 kHz
High Pass Filter
Band 2
80 Hz - 3 kHz
Band Pass Filter
Band 1
80 Hz
Low Pass Filter
Compressor
3
Compressor
2
Compressor
1
Adder
Compressor
Network
Input
Output
Compressor
Network
A
B
A
A
B
B
Compressor
4
Figure D-1: Dolby A-type Noise Reduction Basic Block Diagram
(–)
Sliding Band
-----------------
Fixed Band
Sliding Band
----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
Sliding Band
-----------------
Fixed Band
LF & HF
Spectral
Skewing
LF & HF
Spectral
Skewing
LF
Anti-
Saturation
HF
Anti-
Saturation
HF
Anti-
Saturation
LF
Anti-
Saturation
+
+
+
+
+
+
Signal
Input
ENCODER
High Level Stages
Mid High Level
Low Level Stages
High Level Stages
Mid High Level
Low Level
DECODER
HF
HF HF
HF
HF HF
LF
LF
LF
LF
(–)
(–)
(–)(–)
Signal
Output
Encoded signal
to recorder
Figure D-2: Dolby Spectral Recording Encoder and Decoder Basic Block Diagram