Transcript Audio Video Production Engineering

Metropolitan
Community
College
Audio Video Production
Engineering
Part 1 Audio
Rev. 6.4f
This PowerPoint and other resources may be found at:
http://faculty.mccneb.edu/ccarlson/vaca1010.htm
Nature of Sound Waves
Sounds in air are commonly
produced Vocal cords,
Speakers, Instruments,
etc.
2
Air particles
As the sound source pushes
against air particles they
are compressed.
As the sound source moves
away they are rarefied.
3
4
Loudness VS Distance
Loudness follows an
Inverse-Square Law
Intensity of sound is
inversely proportional to
the square of the distance
from the source.
5
Sound and Hearing
The Human Ear
Outer Ear
Middle Ear
Inner Ear
6
Labyrinth
7
Courtesy of Dr. John S. Oghalai
Used by permission
Pinna
8
Courtesy of Dr. John S. Oghalai
Used by permission
Frequency and Sound
9
20 Hz
960 Hz
60 Hz
1920 Hz
120 Hz
3840 Hz
240 Hz
7680 Hz
480 Hz
15360 Hz
10
Wavelength &
Frequency
11
Amplitude & Phase
12
2
1
3
In phase
0
4
8
5
7
6
2
1
3
90 degrees out of phase
0
4
8
5
6
2
1
7
3
180 degrees out of phase
0
4
8
5
7
6
13
Decibel
Unit of measure Bel
Based on ratio
Used for both Acoustic and
electrical applications
14
dB formulas
Power
dB = 10 log (P1/P0)
Voltage and Acoustic
dB = 20 log (E1/E0)
15
dB as Unit of Measure
Requires a reference
3 and 10 rule (power)
6 and 20 rule
16
3 & 10 and 6 & 20 Rule
17
Power
3 dBW
10 dBW
Other
6 dB
20 dB
Multiplier + X 2
X 10
Multiplier - ÷ 2
÷ 10
Add and Subtract dB
18
dB change
Total
Result
+6 dB
6 dB
X2
+6 dB
12 dB
X4
+20 dB
32 dB
x40
dB Standards
0 dBW = 1W
100W amplifier is 20dBW
1000W amplifier is 30dBW
19
dB Standards
0 dBm = 1mw>600 Ohm
load (.775 V)
0 dBu = .775 V
0 dBv = .775 V
0 dBV = 1 V
20
Click chart for sound
21
SPL Meter
Microphone Amplifier Meter
A Weighting filter inverse of
equal loudness contours
B & C Weighting high end
of equal loudness contours
22
Weighting Networks
A weighting 10 – 55 dB
B weighting 55 – 85 dB
C weighting 85 – 140 dB
23
Weighting Chart
24
Loudness of sound (dB)
Threshold of hearing
0
Normal conversation
60
City traffic inside car
85
Sustained exposure results in
hearing loss
85-90
Power Mower
107
25
Loudness of sound (dB)
Rock concert front row
Pain begins
Jet engine @ 100’
Death of hearing tissue
Loudest sound possible
26
115
120
140
180
194
dB Meter
Specialized AC Meter with
scale calibrated in dB
27
VU Meter
Much the same as dB meter
Calibrated 0VU = __dB
Response peak to average
Analog, LED, Electronic
display
28
Noise Induced
Hearing Loss
Base level 85 dB for 8 hrs
Each 3 db increase 1/2 time
“A” weighting measurement
Most sensitive at 4 KHz
40 yrs @ 85dB = NIHL 8%
29
30
End Week 1
Review Week 2
31
32
Magnetic Polarity
Like Poles Repel
Unlike Poles Attract
33
N
Magnetic
Field
S
0
-
Direction
of Travel
Magnetic
Field
+
.
0
-
+
Direction
of Travel
Direction
of Travel
0
Magnetic
Field
+
34
+
Electromagnetic
Interference
A Moving magnetic field
across a stationary
conductor has same effect
as a moving conductor in
a stationary magnetic field
35
Magnetic field is generated
around wires carrying
current
Magnetic polarity changes
as direction of current
flow changes
36
Capacitors
Two metallic plates
Insulated from each other
(insulation called dielectric)
37
38
Capacitors store
electrons
Capacitors behave much
like a water tower
Filling the water tower is
like charging a capacitor
Using the water is like
discharging a capacitor
39
Unit of Measure
The Farad is the unit of
measure. Typical values
are Micro Farad or Pico
Farad. Larger values store
more electrons.
40
Capacitor Behavior
Capacitors block DC current
and pass AC current
41
Capacitor Behavior
42
Output
Moving coil
attached to
Diaphragm
N
S
Dynamic
Microphone
Diaphragm
Diaphragm
(front plate)
Back plate
(fixed)
Output
Spacer
Capacitor
Microphone
Ribbon
Microphone
43
A microphone sensitivity
specification tells how
much electrical output (in
thousandths of a volt or
"millivolts") a microphone
produces for a certain
sound pressure input in
dB SPL (usually 94dB SPL)
44
If two microphones are
subjected to the same
sound pressure level and
one puts out a stronger
signal (higher voltage),
that microphone is said to
have higher sensitivity.
45
Microphone Pickup
Patterns
Omni-directional: picks up
sound from all directions
Directional: picks up sound
from one direction
Bi-directional: picks up
sound from two directions
46
Pick-up Patterns
47
Polar Pattern
48
Directional Microphones
Directional Microphones
called Cardioid,
Supercardioid,
Hypercardioid
49
Directional Microphones
Proximity effect
Do not “reach” further
Generally do not have as
smooth of a response
curve as Omni-directional
50
Phantom Power
2
3
1
51
Muting Capacitor Mics
52
Muting Capacitor Mics
53
The 3 to 1 rule
The distance between
microphones should be at
least 3 times the distance
from each microphone to
its intended sound source.
54
Comb Filtering
55
Connecting to Cameras
Front input and Back input
Select Mic. or Line
If Mic., Phantom on or off
Select Auto or Manual levels
Assign which is Ch.1 or Ch.2
56
How Speakers Work
http://electronics.howstuff
works.com/speaker5.htm
57
Block Diagrams
Used to make complex
circuits or systems easy
for the user to
comprehend and use
58
Block Diagrams
Most common symbol is a
square or rectangle
Triangles often used
Interconnected by lines
59
Block Diagrams
Direction of lines important
INPUTS – top and left
OUTPUTS - bottom and
right
Use arrows when not
standard
60
Blue lines SDI
Black lines Composite
61
62
63
Amplifiers
Electronic devices used to
increase an electronic
signal level
Many types and kinds
64
Amplifier
Characteristics
Gain
Impedance input/output
Balanced input/output
Unbalanced input/output
65
Audio Amplifier Types
Pre amplifier
Buffer amplifier
Line amplifier/DA
Power amplifier
66
Pre Amplifier
Frequently used in low level
applications
Phonograph cartridge
Microphone
Intercom
67
Buffer
Often used to isolate one
circuit from another and
to match impedances
68
Line Amplifier/DA
Often used to increase
drive capability
Split signals to feed several
different pieces of equipt.
Usually no change in level
69
Power Amplifiers
Usually used to increase
current capability to drive
speakers and headphones
70
Combining Speakers
Speakers connected in
Series, Z adds directly
Speakers connected in
Parallel, If Z is all the
same value, Total Z =
Z/Number of spkrs.
71
Combining Speakers
If Z has different values
calculate using:
1
Z total = 1 + 1 + 1
Z1
Z2
Z3
72
Distributed Sound
Add All tap values in system. Amp power
used should be 80% of amp rating
73
End Week 2
Review Week 3
74
Ohm’s Law
E=IR
E is voltage in volts
I is current in amps
R is resistance in Ohms
75
Rearranging Formula
E=IR
I=E/R
R=E/I
76
Power Law (Watt’s Law)
P=IE
P is power in watts
I is current in amps
E is voltage in volts
77
Rearranging Formula
P=IE
I=P/E
E=P/I
78
P=I R
2
P=E /R
2
Electrical Circuit Rating
Most modern circuits for
outlets are 120 V 20 A
2400 watts are available
per circuit
Codes vary for how many
outlets can be on a circuit
79
Impedance
The total opposition to an
alternating current and is
measured in Ohms
Symbol for impedance is Z
80
Complex calculations
Impedance = square root
of reactance squared +
resistance squared.
81
Reactance & Frequency
Capacitive Reactance
Xc=1/2∏fC
Inductive Reactance
Xl=2∏fL
82
Wiring Characteristics
Impedance and Resistance
Impedance for AC circuits
Resistance for DC circuits
Both measured in Ohms
83
Measurement
Resistance measured
directly with meter
Impedance calculated or
measured with bridge
84
Bridge Measurement
Reference
Unknown
AC
signal
0
-
+
Meter
Reference
85
Adjustment
Cable Characteristics
Conductor size (AWG)
Number of Conductors
Twist or no twist
Shielding
Insulation type
86
AWG
24-26 Guage used for
Phone & Computer wiring
22 Guage often used for
Audio Mic. & Line level
16-18 Guage 70V Speaker
distribution
87
AWG
18-10 Guage used for 2 Ω 16 Ω speakers
88
Number of Conductors
Unbalanced audio 1
conductor plus shield or
ground connection.
2 conductors needed to
complete circuit
89
Number of Conductors
Balanced audio 2
conductors, may also have
a shield but not required
Speaker 2 conductors with
no shield
90
Twist or No Twist
Twisted pairs used with low
level audio and many
other services (data,
phone, etc.)
No twist mainly for power
91
Shielding
Shield must be connected
on both ends for Phantom
powering of microphones
Connecting shields on one
end may be good for hum,
but increases RFI chances
92
Phantom Power
2
3
1
93
Insulation Type
Plenum and non-plenum
Portable and Installed wire
RoHS compliant
94
RoHS Compliant
The RoHS directive aims to
restrict certain dangerous
substances commonly
used in electronic and
electronic equipment
(Restriction of Use of Hazardous Substances)
95
RoHS Compliant
. Any RoHS compliant
component is tested for
the presence of Lead (Pb),
Cadmium (Cd), Mercury
(Hg), Hexavalent
chromium (Hex-Cr),
96
RoHS Compliant
Polybrominated biphenyls
(PBB), and
Polybrominated diphenyl
ethers (PBDE). Some
97
military and medical
equipment are exempt from
RoHS compliance.
Common Connectors
98
99
Speaker Wiring
Speaker Wire Chart
100
Copper
Wire
Size
2
Ohm
4
Ohm
6
Ohm
8
Ohm
22
3
6
9
12
20
5
10
15
20
18
8
15
23
30
16
12
25
37
50
14
20
40
58
77
12
31
61
92
123
10
50
98
147
196
Maximum loss of 5% of nominal speaker
impedance.
Example 8 Ω speaker, 5% = .4 Ω.
22 gauge wire has resistance of 0.0164
Ω per foot
1 wire each way (2 wires) = 0.0328 Ω / Ft.
.4/.0328=12.195 or 12' for 5 % loss.
Wire Calculator
http://circuitcalculator.com
/wordpress/2007/09/20/w
ire-parameter-calculator/
http://en.wikipedia.org/wiki
/American_wire_gauge
101
Balanced Wiring
Input
+
X
-
102
Output
Common Mode Rejection
+
Common Mode
-
103
X
Output
Unbalanced Wiring
Input
104
+
Output
Audio Class of Service
105
Microphone level (-50 dB)
Line level (0 dB)
Speaker level
Video (1V Noisy)
RF (Saturates Amplifiers)
Data (HF Noisy)
End Week 3
Review Week 4
106
Equipment
Interconnect
Power Grounding
Earth/Chassis
Signal Grounding
107
Ground Loops
108
Transformers
Turns Ratio
Step-up/Step-down
Impedance
Other Properties
See also
http://www.energyquest.ca.gov/how_it_works/transformer.html
109
Transformers
Isolation
+
Step-down
+
+
+
Polarity
110
Polarity
Step-up
Transformer Isolation
111
Courtesy Rane Corporation (RaneNote 110)
Used by permission
Power For Equipment
112
Two Bus for 220V
113
Patch Panels
1
25
From Equipment (Outputs)
To Equipment (Inputs)
Normalling Jack Pair
114
24
48
The right way to do it.
115
Courtesy Rane Corporation (RaneNote 110)
Used by permission
116
Courtesy Rane Corporation (RaneNote 110)
Used by permission
See Also
EPM Mixer
guide pg 30
(A) Off the
Shelf cable
(B) 6dB sig.
loss
117
Courtesy Rane Corporation (RaneNote 110)
Used by permission
118
Courtesy Rane Corporation (RaneNote 110)
Used by permission
119
Courtesy Rane Corporation (RaneNote 110)
Used by permission
Shortcuts
+ Tip
+ Pin
Shield
+ Pin 2
- Pin 3
Shield
Pin 1
120
Shield
(Sleeve)
- Ring
+ Tip
Balanced to Unbalanced
+ Pin 2
Balanced
Output
- Pin 3 N/C
Shield
Shield Pin 1
+ Pin 2
Balanced
- Pin 3 Input
Shield Pin 1
121
Jumper
Soldering Connectors
See “A guide to soldering”
and “EPE basic soldering
guide” on my Website
122
Soldering Video
RCA connectors
¼” connectors
XLR connectors
123
Equalization
Very complex topic
1. Sound reinforcement
2. Vocal
3. Instruments
124
Sound Reinforcement
There is no one correct way
to equalize a sound
system. Type of system
and size of the space has
a giant impact EQ
technique.
125
Distributed Sound
Using Parametric EQ, try to
adjust the system EQ
using pink noise and
spectrum analyzer for
near flat response (slight
HF roll off OK)
126
System EQ
Once System EQ is
adjusted, individual vocal
channels or instrument
channels may be adjusted
for “BEST MIX”
127
Basic Terms
Octave
An octave is the interval
between two points where
the frequency at the
second point is twice the
frequency of the first.
128
Frequency & Octaves
63 Hz 1
250 Hz 3
1 KHz 5
4 KHz 7
16 KHz 9
129
125 Hz
500 Hz
2 KHz
8 KHz
2
4
6
8
“Q” rating
The "Q" control sets the
width of the band of
frequencies that will be
boosted or reduced
130
“Q” Chart
Q Setting
0.7
1.0
1.4
2.8
131
Bandwidth
2 Octaves
1 1/3 Octaves
1 Octave
1/2 Octave
Equalizer Types
Graphic equalizer, Several
varieties
Shelving (highpass-lowpass)
High or low cut or boost
Parametric, Boost, cut,
center freq & Q
132
Speech Characteristics
Cover three main frequency
bands
Fundamentals
Vowels
Consonants
133
Fundamentals
125 – 250 Hz
Essential for voice quality
(who is speaking)
315 – 500 Hz also
important to voice quality
134
Vowels
Contain the maximum
energy & Power of the
voice 350 Hz – 2,000 Hz
630 – 1 KHz Important for
natural sound
135
Consonants
1,500 – 4,000 Hz contain
little energy but are
essential to intelligibility
1.25 – 8 KHz governs the
clarity of vocals
136
Energy
63 – 500 Hz contain 60%
power and 5% intelligibility
500 – 1 KHz contain 35%
power and 35% intelligibility
1K – 8 KHz 5% power and
60% intelligibility
137
EQ Problem…Vocals
Boost 100 – 250 Boomy
Cut 150 – 500 Boxy, Hollow
Cut 500 – 1 KHz hardness
Boost 1 – 3 KHz metallic
Cut 2 – 5 KHz lifeless
Boost 4 – 10 KHz gritty, sibilance
138
General Tips
Be sure level is correct before
EQ (don’t use EQ to make up for low level)
Boost less Cut more
Do not boost fundamentals
Avoid boosting the same
frequency for 2 instruments
139
General Tips
Do not use EQ to make-up for
poor microphone placement
Keep track of what works best
for your mixes. Use notes as
starting point to save time
during sound check
140
Equalization Primer
Follow link for more information
about equalization.
http://www.menet.umn.edu/~kgei
sler/EQ/primer.htm
http://tweakheadz.com/EQ_and_t
he_Limits_of_Audio.html
141
End Week 4
Review Week 5
142
Magnetic Tape
Back coat
Plastic base
Binder
Magnetic coating
143
144
Magnetic Tape
Several different coatings
Iron oxide
Chromium dioxide
Cobalt Doped
Metal
145
Magnetic Tape
Properties
Not detailed in this class
Coercivity, Retentivity,
Sensitivity, Print through,
Dropout, and many more
146
Recording Process
Recording is non-linear at
audio frequencies
Bias current is needed to
make recording linear
Bias adjustment depends
on type of tape
147
Bias
Frequency Around 100 KHz
Applied to Erase Head
Modulated by Audio
148
149
Mix Bus
Common point where
multiple signals are
combined
Summing point
150
Attenuators
Used to reduce signal level
Many types
Gain controls do not do the
same thing
151
Refer to EPM Mixer
Guide
Functional description
Block Diagram
How to use some functions
152
153
154
155
156
157
158
159
160
161
162
163
164
165
Audio Studio Photos
166
Audio Studio Photos
167
Audio Studio Photos
168
End Week 5
Review Week 6
169
Digital Audio
A to D Process
Storage
D to A Process
170
A to D Process
Sampling Rate
How many times per
second is the analog
signal looked at
CD is 44,100/Sec
171
Sampling vs Frequency
Sampling rate needs to be
twice the frequency of the
highest audio frequency
needed
172
Analog Signal
Sample Points
Sample Rate
173
Anti-aliasing
A low pass filter us used to
limit high frequencies
prior to sampling
174
Number Systems
Decimal
Binary
Others; octal, Hexadecimal,
etc.
175
Weighting
Number
System
Symbols
Binary
Decimal
Hexadecimal
F E D
C
104
Decimal
Binary
176
B
A
0
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
0
103
10,000
1
102
1,000
101
100
100
10
1
27
26
25
24
23
22
21
20
128
64
32
16
8
4
2
1
16 bit Binary
177
1-1, 2-2, 3-4, 4-8, 5-16,
6-32, 7-64, 8-128, 9-256
10-512, 11-1024, 12-2048,
13-4096, 14-8192,
15-16384, 16-32768,
17-65536
178
Quantization
The Value of each sample
Two 8 Bit words (16 bits)
yields 65,536 graduations
(used for each CD
channel)
179
180
Modulated
#132
1
Clock
181
2
4
8
16
32
64
128
The D to A Process
Demodulation
Error Correction
D to A Conversion
Sample and Hold
Low Pass Filter
182
Demodulation
Restores the recorded
signal to original ones and
zeros
183
Error Correction
Compensates for errors
introduced during the
recording process
184
D to A Conversion
Electronic process that
converts digital numbers
(samples) into analog
voltage (current)
185
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/dac.html#c3
186
Sample and Hold
Circuits that remove
“Switching Glitches” that
appear after D to A
processing
187
Low Pass Filtering
A circuit that does the final
smoothing of the analog
signal and removes any
high frequency noise
188
Sample Rate Demos
Sample rate demo
Anne Murray
“You Needed Me”
189
File Conversion
http://www.nch.com.au/inde
x.html
Free tools for both Mac & PC
Advanced tools for purchase
190
File formats
http://www.nch.com.au/switch/kb/1405.html
www.nch.com.au/acm/formats.html
191
File format conv. from
.aac
.3gp .aif/aiff/aifc
.amr .ape .au
.asf
.avi
.caf* .cda* .dct
.ds2 .dss* .dvf* .flac
.flv
.gsm .m3u* .m4a
*not supported on Mac
192
File format conv. from
.m4r* .mid*
.mov .mp2*
.mpga*.mpg
.pls* .ra*
.spx* .sri*
.wav .wma
193
.mod
.mp3
.msv*
.raw
.voc
.wmv
.moh
.mpc
.ogg
.shn
.vox
.wv
File format conv. to
.aac
.aif/aiff/aifc .amr
.ape* .au
.caf* .flac
.gsm .m3u .m4a .m4r*
.mov# .mpe .mpc .ogg
.pls
.raw .spx* .vox
.wav .wma* *not Mac #not Windows
194
Menu item options
195
Menu item options
196
Wiring Considerations
Most digital connections use
standard XLR connectors
wired the same as
balanced audio
Do not bundle/run with
audio cabling
197
Wiring Considerations
Most MIDI hardware uses
DIN-5 pin connections
Pins 4 & 5 carry digital
signal Pin 2 is shield
50 ft maximum length
198