Download - LTspice audio simulation
LTSPICE AUDIO SIMULATION:
A LOUDNESS CONTROL
Bee Technologies Inc.
20AUG2012
1
EQUAL-LOUDNESS CONTOUR
Equal-loudness contour is a measure of sound pressure (dB SPL), over
the frequency spectrum, for which the human ear perceive the same
loudness when presented with pure steady tones (unit is the phon).
For more info . . .
http://www.sfu.ca/sonic-studio/handbook/Equal_Loudness_Contours.html
40
60
80
100
120
10 100 1000 10000
INT
EN
SIT
Y L
EV
EL
(d
B)
FREQUENCY (Hz)
100
90
80
70
60 Loudness level (phon)
Contours of equal loudness (from the Radiotron Designers Handbook).
2
A LOUDNESS CONTROL
A loudness control is used as an attempt to restore extreme low and high
frequencies. As the sound level decreases, the ear becomes less sensitive
to both extreme low and high frequencies. Thus, when listening at reduced
levels, if the frequency response of your system is maintained flat, you will
not hear those extremes as well.
C176.9739p
PARAMETERS:
RVOL = 500k
VOL = 0.0245
PARAMETERS:
RVOL1 = {(1-VOL+1u)*RVOL}
RVOL2 = {(VOL+1u)*RVOL}
RVOL-2
{RVOL2}
RVOL-1
{RVOL1}
Output
V11Vac
0Vdc
Input
0
R1
200k
0
C258.7883n
R22.2119meg
R3330
R42MEG
L120m
1
2
R5
4.6695k
C3
3.9244n
Frequency
100Hz 1.0KHz 10KHz20Hz 50KHz
DB(V(OUTPUT))
-60
-40
-20
0
20
DB(V(OUTPUT))
A loudness control and its frequency response (example)
3
THE LOUDNESS CONTROL VS. EQUAL-LOUDNESS CONTOUR
-60
-40
-20
0
20
10 100 1000 10000
INT
EN
SIT
Y L
EV
EL
(d
B)
FREQUENCY (Hz)
100
100(Sim)
90
90(Sim)
80
80(Sim)
70
70(Sim)
60
60(Sim)
Frequency response of the loudness control (simulation) is compared to the equal-loudness contour.
4
Loudness Control vs. Flat Volume
C176.9739p
PARAMETERS:
RVOL = 500k
VOL = 0.0245
PARAMETERS:
RVOL1 = {(1-VOL+1u)*RVOL}
RVOL2 = {(VOL+1u)*RVOL}
RVOL-2
{RVOL2}
RVOL-1
{RVOL1}
Output
V11Vac
0Vdc
Input
0
R1
200k
0
C258.7883n
R22.2119meg
R3330
R42MEG
L120m
1
2
R5
4.6695k
C3
3.9244n
C176.9739p
PARAMETERS:
RVOL = 500k
VOL = 0.0245
PARAMETERS:
RVOL1 = {(1-VOL+1u)*RVOL}
RVOL2 = {(VOL+1u)*RVOL}
RVOL-2
{RVOL2}
RVOL-1
{RVOL1}
Output
V11Vac
0Vdc
Input
0
R1
200k
0
C258.7883n
R22.2119meg
R3330
R42MEG
L120m
1
2
R5
4.6695k
C3
3.9244n
LOUDNESS CONTROL FLAT VOLUME
The High-Pass
circuit is
disconnected, the
Low-Pass circuit
is short to ground
5
Frequency
100Hz 1.0KHz 10KHz20Hz 50KHz
DB(V(OUTPUT))
-60
-40
-20
0
20
Frequency
100Hz 1.0KHz 10KHz20Hz 50KHz
DB(V(OUTPUT))
-60
-40
-20
0
20
DB(V(OUTPUT))
Loudness Control vs. Flat Volume
LOUDNESS CONTROL RESPONSE FLAT VOLUME RESPONSE
6
LTspice Simulation: .WAV IN/OUT Loudness Control
Loudness Control with .WAV input and output Simulation result: input and output signal
Low to high swept audible signal (Input)
-30 dB level down with the loudness control (Output)
7
LTspice Simulation: .WAV IN/OUT Flat Volume
Flat Volume with .WAV input and output Simulation result: input and output signal
Low to high swept audible signal (Input)
-30 dB level down with the flat volume (Output)
8
.WAV FILES LOCATION
An input file Output files created
by LTSpice
9
USING WAVE FILE (.WAV) AS INPUT
Using audio signal (WAVE file) as an input voltage for LTSpice could be done
by replace the voltage expression of the voltage source with a WAVE-file
expression: wavefile=“file location" chan=0 (as seen in the example
below)
“chan” refers to the respective channel in the WAVE file used for the
simulation, can be a number between 1 and 65535 although usually
channel 0 refer to the left channel and channel 1 refers to the right channel
A loudness control and its frequency response (example)
10
USING WAVE FILE (.WAV) AS OUTPUT
Exporting an output signal as an audio signal (WAVE file) could be done by
adding SPICE directive as: .wave=“file location" 16 44100 Output (as
seen in the example below)
“16” refers to the bitrate, 44100 is the sampling frequency and Output is
referring to a label in circuit.
A loudness control and its frequency response (example)
11
LTspice Simulation: music01.WAV IN/OUT Loudness Control
Loudness Control with music01.WAV input and output Simulation result: input and output signal
music01.wav audio signal (Input)
-30 dB level down with the loudness control (Output)
12
LTspice Simulation: music01.WAV IN/OUT Flat Volume
Low to high swept audible signal (Input)
-30 dB level down with the flat volume (Output)
Flat Volume with music01.WAV input and output Simulation result: input and output signal
13
.WAV FILES LOCATION
An input file
Output files created
by LTSpice
Output files created
by LTSpice
14
VIDEO DEMONSTRATION
15