Training
 www.paformusic.info Training |
An information site such as this one cannot substitute for professional training that includes practical hands-on experience of working with live performers.
Below you will find a structured list of topics, intended as a guide to the kind of material that would be covered in a comprehensive live sound engineering course; this may be of assistance in evaluating courses on offer. Remember, however, that a course may cover incidentally many topics that are not explictly advertised.
You can also use this page as a list of topics to assist in evaluating or refreshing your present knowledge. Many of the topics have links into the Glossary, which you can follow for a reminder of what they are about. If you can think of anything missing from this list, please let me know.
Contents
- Basics
- The Nature of Sound
- Electrical Fundamentals
- Electrical Signals
- Microphones
- Speakers
- Amplifiers
- Signal Interconnections
- Effects
- Mixers
- Power Distribution
- Safety
- Care of Equipment
- System Design & Assembly
- System Operation
- Problem-Solving
- Buying to a Budget
- Introduction to Recording
Basics
- The need for
sound reinforcement
- A brief history of sound reinforcement
- Unamplified vocals & acoustic instruments − greater sound level required more performers − large orchestras & large choirs
- Amphitheatre solution for speech and acoustic instruments
- Pipe-organ solution for music in large venues (not just churches)
- Capital & maintenance expense drove electronic organ development (dance halls, cinema)
- Position maintained until 50's/60's music revolution − amplified instruments & vocals
- Advancements in materials technology allowed increasingly powerful speakers of high quality at moderate size & weight
- Advancements in electronics (particularly the advent of integrated circuits) allowed increasing equipment functionality, features & complexity along with decreasing size & weight
- Operated versus non-operated systems
- The system came first, then the operator
- Who is capable of the task?
- Mixer location − stage versus audience
- Sound engineering
− or art?
- Taste, preference & opinion − 'painting a sound'
- Technical aspects of system design & assembly
- Technical aspects of operation & problem-solving
- The role of the sound engineer
- A brief history of sound reinforcement
- The primary system components
- Microphones
- Purpose
- Very many types − suited to application (target sound + environment) & to budget
- Mixers
- Purpose (simplest arrangement)
- Channels
- Master section
- Power amplifiers
- Purpose
- May be integrated within mixer or within speakers
- Speakers
- Purpose
- Very many types − application, power handling & environment
- Equipment interconnections
- Microphones
The Nature of Sound
- Pressure waves
- Velocity
dependent on medium
- Density
- Velocity
dependent on medium
- The behaviour of waves
- Dispersion
- Absorption
- Surface
- Medium
- Reflection
- Refraction
- Diffraction
- Environmental factors
- Temperature
- RH
- The grazing effect
- Surface dependence
- Auditory response
- The nature of hearing
- Physical and perceived sound
- Mechanical & neural mechanisms
- Psycho-acoustics
- Response to pitch
- Response to level
- Logarithmic
- Frequency dependence
- Directionality
- Stereo
- Front/back cues
- Hearing loss mechanisms
- Pitch and frequency
- Musical pitch expressed as frequency
- Octaves
- Lower and upper frequency limits of hearing
- Human − compare dog, bat, whale
- Typical frequency ranges of voice and instruments
- Male & female voice
- Piano
- Guitar & bass
- Percussion
- Fundamentals and harmonics
- Timbre
- Complex sounds
- SPL and
dB
- SPL versus perceived level
- The threshold of hearing
- Dependence on frequency
- The threshold of pain
- Balancing levels − masking effect
- The dB SPL scale
- Measurement
- A weighting
- C weighting
- Response time
- Min / max
- Average over time
- The speed of sound
- Dependence on medium and temperature
- Time delay
- Consequence for secondary speakers
- Echoes
- Wavelength
- Relation to frequency
- Resonance
- Objects
- Spaces
- Room acoustics
- Reverberation
- Pros & cons for listening
- RT-60
- Room size and shape
- Wavelength-dependent effects
- Reverberation
- Stereo
- Sound source location
- Sweet spot
- Front / rear effects
- Surround sound
- The Haas effect
- The consequences for stereo sound
- Binaural recording
Electrical Fundamentals
- Basic electrical principles
- AC circuits
- Waveforms & frequency
- Instantaneous values & RMS values
- Capacitance
- Inductance
- Impedance
- Power in AC circuits
- Capacitive and inductive effects in cables
- Characteristic impedance
Electrical Signals
- Analogue
signal principles
- Sound waves represented as an electrical waveform
- Levels
- Instantaneous values
- RMS voltage
- Typical signal levels
- dBV,
dBm and
dBu
- The 600 ohm reference circuit
- The 0.775 V reference voltage
- Standard levels −10 dBV & +4 dBu
- Gain and
attenuation
- Level variations
- Average level, nominal level
- Peak level
- Transients
- Headroom
- Noise & signal-to-noise ratio
- Dynamic range
- Interconnection issues
- Input impedance
- Output impedance
- Voltage-matched
- Impedance-matched
- Unbalanced / balanced
- Phase & polarity − in-phase & anti-phase signals
- See also Signal Interconnections
- Digital and
optical signals
- Sampling & A/D conversion
- Levels, dB FS
- Multiplexing
- AES3 &
S/PDIF
- Frame structure
- Subcode information
- Physical interfaces − unbalanced, balanced, optical
- Cabling requirements − characteristic impedance, distance limits
- MADI (AES10)
- ADAT
Microphones
- Purpose and principles
- Application requirements
- Huge variety of models
- On/off switches
- Pros & cons
- Leakage
- 3-to-1 rule
- Application requirements
- Polar response
- Omni-directional
- Cardioid
- Subcardioid
- Super-cardioid
- Hyper-cardioid
- Rifle / shotgun / lobar
- Switchable
- Frequency response
- The proximity effect
- Switchable low- & hi-cut
- Sound level factors
- Sensitivity
- Maximum SPL
- Switchable pads
- Impedance
- High impedance types
- Low impedance types
- Significance for cable type, length & connectors
- Dynamic types
- Principle of operation
- Ruggedness (except ribbon types)
- Condenser types
- Principle of operation
- Electret / true condenser / RF types
- Higher sensitivity
- Better top-end response
- Fragility
- Power requirement
- Battery
- Phantom
- Boundary types
- Sensitivity advantage
- Typical usage
- Mounting methods
- Physical & effectiveness factors: type & distance of source, movement of source
- Visual factors: hidden mic / performance prop / mouth visibility
- Hand-held
- Stands
- Straight
- Boom
- Gooseneck
- Clip sizes − for condenser & radio mics
- Thread sizes & adaptors
- Lapel clipped (lavalier)
- Omni / Cardioid
- Importance of correct positioning
- Instrument clipped
- Headset
- Close proximity
- No relative movement
- Suspended
- Floor, gantry/bar, hair (theatre)
- Radio /
Wireless types
- Pros & cons
- Freedom
- Batteries − rechargeables
- Principle
- Hand-held mic transmitters
- Built-in
- Plug-on
- Compare mute and power on/off switches
- Body-worn transmitters
- Lavalier / headset mic
- Instrument
- Flexible inputs
- Receivers
- Importance of location
- Twin antenna
- True diversity
- Antenna distribution
- RF impedance matching
- BNC connectors
- Subject to phantom power
- VHF and
UHF types
- Interference
- Tunability
- Regulated &
de-regulated
frequencies
- Co-channel interference
- Single-site licencing
- Multi-site licencing
- Receiver noise
- Dynamic range limitations
- Companding
- Operating range
- Receiver sensitivity & squelch
- Pros & cons
- Handling noise and breath-blast noise
Speakers
- Purpose and principles
- Power handling
- Thermal & mechanical limits
- Average power & the 'RMS power' misnomer
- Music power
- Peak power
- Connector types
- Speaker protection
- Power compression
- Sensitivity
- Relationship to power-handling & max SPL requirement
- Frequency response
- Passive crossovers
- Bi- and tri- amping
- Power spread across
spectrum
- Consequence for speaker & amplifier power requirements
- Active crossovers
- Importance of correct frequency-band connections
- Power spread across
spectrum
- Processor
control
- Dispersion angles and
throw
- Audience orientation
- Narrow & deep
- Wide & shallow
- Square
- Rising seating
- Line arrays
- Critical distance
- Maximum frequency of behaviour
- Audience orientation
- Impedance
- Parallel,
series &
series-parallel
connection
- Importance of correct polarity
- Effect on power output
- Mixed impedances
- Parallel,
series &
series-parallel
connection
- Powered speakers
- Advantages
- Disadvantages
- Mounting methods
- Free-standing
- Stands
- Brackets
- Flown
- Safety issues
- Monitor speakers
- The need for monitoring
- Floor monitors
- Stand-mounted
- Side-fill
- In-ear monitoring
- Headphones
- Typically for drummers
- Pros & cons of radio systems
- Freedom of movement
- Performer-adjustable
- Batteries − rechargeables
- Disorientation
- Safety − acoustic levels
- Own / mix balance control
- Multiple receivers
- Consequence for own/mix balance
- Headphones
- 100 volt line
speakers
- Transformer power
tappings
- Effect on amplifier/cable loading
- Transformer power
tappings
Amplifiers
- Purpose
- Referring here to power amplifiers
- Connecting to speakers
- Direct connections when sufficient outputs provided
- Speaker daisy-chaining
- Importance of correct polarity
- Impedance matching
- Parallel speaker
connections
- The effect of total load impedance on power drawn
- Determining the total load impedance
- Impedance limits
- Lower limit − all amps
- Upper limit − valve amps only (rare in PA)
- Parallel speaker
connections
- Power matching
- Power rating
- Amplifier overload dynamics
- Comparison with speaker overload dynamics
- Bridging
- Purpose
- Method
- Cautions
- Suitability of amplifiers
- Effect on minimum load impedance
- Input levels
- Level controls
- Level indicators
- 100 volt line
systems
- Electrical safety − band II insulation
- Zoning & cabling arrangement
- Incompatibility
- Induction loops
- Legal requirements
- DDA requirements (UK)
- Examples of public services
- Principle
- Current driven
- User dependence
- Suitable hearing aid
- Knowledge of how to use (T-position)
- Awareness of facility − signage
- User focus
- May be unable to hear other sounds
- Frequency response
- Dynamic range
- Installation
- Loop area, shape & height
- Loop resistance − cable gauge
- Cable protection
- Avoidance of stage area
- Interference factors
- Testing
- Legal requirements
- Heat dissipation
- Efficiency
- Ambient temperature
- Temperature rise in racks
- Heatsinks
- Convection cooling
- Forced cooling
- Classes of
amplifier
- A, B, AB, G, D/S
- Crossover distortion
- Protection
- Amplifier
- Speaker
- Power-on delay (thump protection)
- DC offset
Signal Interconnections
- Analogue
and digital types
- Applications
- Advantages and disadvantages; contrasting characteristics
- Interference immunity, digital cliff
- Connector
types and their application
- XLR
- Jack
- Combined XLR and Jack sockets
- Phono / RCA
- Mini XLR
- Mini jack
- 2.5 & 3.5 mm
- 2 & 3 pole − mono & stereo
- 4 pole TRRS
- DIN
- 2 to 8 pole
- 180° & 270°
- MIDI
- Mini DIN
- Speakon
- 2, 4 & 8 pole
- Limited intermating
- Frequency-band compatibility cautions
- BNC
- Multi-way
- Optical
- TOSLink
- 3.5 mm
- General purpose digital
- Cable types
and their application
- Physical attributes
- Thickness
- Flexibility
- Resilience to wear & tear
- Maximum voltage
- Maximum current
- Maximum operating temperature
- Flammability, low smoke and fume (LSF)
- Characteristic impedance
- Microphony
- Sheath colour
- Maximum bit-rate
- Interference immunity
- Crosstalk immunity
- Screened and
unscreened
- Coaxial
- Screen types
- Drain wires
- Impedance-specified
- Paired (balanced use) and unpaired (unbalanced use)
- Star quad
- Multicore
- Optical
- Application-specific
- Microphone
- Instrument
- Line level
- Speaker
- 100 volt line
- Multicores
- Ethernet
- Physical attributes
- High impedance and
low impedance
interconnections
- Effect on high-frequency losses (and hence on max cable length)
- Unbalanced and
balanced interconnections
- Unbalanced
- Fully balanced
- Current-loop vs symmetrical drive
- Transformer / Electronically balanced (transformerless)
- Quasi-floating
- Partially balanced
- Phase & polarity
- Interference immunity
- Sources & types of interference
- Use of star quad cable
- Digital interconnections
- Balanced / unbalanced
- AES3
- AES3-id
- S/PDIF
- MADI (AES10)
- ADAT
- Dante & RAVENNA
- AES50 & AES67
- DMX
- Importance of
impedance-matching
- Distribution − use of distribution amplifiers
- Correct termination impedance (value and location)
- Correct characteristic impedance of cables and connectors
- Phantom powering
- Principle
- Advantages over battery-driven
- Mixer-driven
- Switching global/grouped/individual
- Inserters
- Cautions
- Not compatible with 'unbalanced DI'
- High-level noise hazard if connections made/broken on open channel
- Thump/click hazard if switched on/off on open channel
- Multicores
- Unpowered
- Combined / separate return cables
- Powered
- Digital multicores
- Cable drums
- Unpowered
- Stageboxes
- Female inputs
- Male outputs (returns)
- Digital stageboxes
- Patch bays
- Purpose
- Use of 3-pole jacks
- Types of jacks used
- Types of normalling
- Direct injection
- Purpose
- Advantages / disadvantages vs microphones
- Connections
- Loop-through
- Passive types
- Advantages / disadvantages
- Active types
- Advantages / disadvantages
- Battery-powered
- Phantom-powered
- Pads
- Earth lift
- Multi-channel
- Radio mic systems
- Balanced / unbalanced output connections
- Antenna distribution units
- Speaker interconnections
- Use of appropriate gauge cable
- Effect of length
- Dependence upon load impedance
- Power loss
- Damping factor
- 100 volt line arrangements
- Number of conductors
- Required rating of connectors
- Installation cabling
- Future-proofing
- Architectural sensitivity
- Protection from damage
- Conduit & trunking
- LSF cables
- Cable testing
- Testing by use
- Commercial testers
- Video connections
- Termination impedance
- Cable characteristic impedance
- Connectors employed
- Standards bodies
- Purpose
- Analogue and
digital types
- Delay
- Mechanical − tape & tube types
- Analogue
- Digital
- Echo
- Based on delay
- Multiple echoes − number & damping
- Reverb
- Mechanical − spring line & plate types
- Analogue
- Digital
- Phasers and
flangers
- Chorus
- Application to solo voice
- Noise gates
- Applications − drums & backline
- Compressors and
limiters
- Compression ratio
- Threshold level
- Average level increase
- Protection applications
- Limiting, not compression, for monitors / IEM
- Side chain filtering/keying
- De-essers
- Purpose and principles
- Channels
- Block diagrams
- System arrangement: for FOH &
monitor
mixes
- On-stage monitor mixing
- Digital vs analogue designs
- Mic inputs
- Line inputs
- Level range
- Typical impedance
- Switched/unswitched − behaviour when mic input is also used
- Stereo channels
- Gain controls and
pads
- Purpose
- Methods of setting
- Phase switch
- Application
- Low-cut switch
- Application
- Channel inserts
- Channel EQ
- Shelving
- Hi / Low
- Slope
- Peaking
- Sweep /
semi-parametric
- Possible absence on stereo channels
- Full parametric
- Shelving
- Channel faders
- Pan controls
- MN-taper
- Different behaviour on stereo channels
- PFL,
solo and
mute
- Use of headphones
- PFL
- Solo-in-place
- Destructive solo
- Sound-checks
- Studio mixdowns
- Mute
- Groups
- Types & their pros, cons & uses
- Audio − mono/stereo
- VCA group
- Mute group
- Selectors
- Relation to pans & stereo mixes
- Group faders
- Types & their pros, cons & uses
- Metering
- Auxiliaries
- Outputs
- Unbalanced / balanced
- Split
- Direct
- Audio groups
- Auxiliaries
- Matrix
- Recording
- FX sends /
returns
- Pre / post fade
- Master/Group inserts
- Purpose
- FX
- Graphics
- Use of 'stereo' jacks
- Linked mode
- Purpose
- Onboard FX
- Types
- Overload
- Graphics
- Internal
- External
- Use with auxiliaries
- Powered mixers and
mixer-amplifiers
- Relation to powered multicores
- Non-operated systems
- Misc
- Talkback
- Illumination
- Needed in dark situations
- Attached to & powered from mixer
Power Distribution
- Adequacy of supply
- Single-phase supplies
- 3-phase supplies
- Cable ratings & types
- Connectors
- Circuit protection
- MDUs / PDUs
- (Also see Safety section)
Safety
- Principles
- Self & others
- Property
- Hazards and risk
- Risk assessment
- Legislation awareness − relevant to country/region
- UK: Health and Safety at Work Act
- UK: Electricity at Work Act
- UK: Public liability
- UK: BS 7909 & BS 7671
- Electrical
- Overview of plugs, fuses/MCBs and distribution
- Overload
- Overheating
- Damage to insulation
- Fire
- Overview of electric shock
- Direct contact
shock hazards
- Damage to insulation or enclosures
- Connectors
- One contact − incidental path to earth
- Two contacts − e.g. guitar/microphone scenario
- 3-phase supplies
- Indirect contact
shock hazards
- Class I − protection by earthing
- Distinction between safety earths & signal earths
- Class II − protection by double insulation
- Cause of hazards
- Class I − disconnection of earths (earth loops)
- Class II − internal equipment damage
- Condition of equipment
- User safety checks
- Formal safety checks & records
- PAT testing
- Reliance on integrity of fixed installation
- Earthing
- Periodic inspection & testing
- RCDs
- Precautions in damp/wet situations
- Outdoors
- Special effects etc
- Fire
- Combustible materials
- Sources of heat
- Selection & use of appropriate fire extinguisher types
- Evacuation procedures
- Fire exits & signage
- Optical
- Intensity, beam-width & distance
- Safe testing
- Connector covers
- Safety
- Dust protection
- Acoustic
- Exposure limits − SPL vs duration
- Safe use of headphones
- Earplugs
- Trip hazards
- Safe routing of cables
- Awareness of normal & emergency access
- Use of gaffer tape
- Use of cable protectors
- Use of hazard tape
- Safe routing of cables
- Drop hazards
- Carry hazards
- Weight awareness
- Lifting technique
- Carrying height
Care of Equipment
- General
- Protection from shock and impact
- Protection from ingress of solids & liquids
- Protection from weather
- Extremes of temperature and humidity
- Flight cases
- Microphones
- Likely modes of abuse
- Drops & knocks
- Saliva & breath
- Inappropriate testing
- Resilience − dynamic vs condenser
- Care during use
- Storage
- Likely modes of abuse
- Speakers
- Driver damage
- Weight-related factors
- Cables
- Cabling damage modes
- Strain
- Abrasion, impact & compression
- Twisting
- Flexibility factors
- Connector damage modes
- Connections − dry joints, conductor/insulation strain, disconnections & shorts
- Strain relief failure
- Contact displacement & loss of contact pressure
- Contact oxidation
- Physical
- Transport & storage
- Anti-twist coiling techniques
- Avoiding tangles − Velcro® ties, cable ties, PVC tape
- Cabling damage modes
- Mixers etc
- Protection from ingress of solids & liquids
- Protection from dust
- Care in cleaning
System Design & Assembly
- Working relationships
- Professionalism
- Managing expectations of systems
- Event/Production Managers
- Venue staff
- Musical Director
- Stage Manager, DSM, ASM
- Other technical staff − sound, lighting, video
- The performers
- The audience
- Unskilled personnel
- Situations
- Installed systems
- Halls
- Theatres
- Commercial − conferences etc.
- Places of worship
- Architectural constraints
- Operator skill levels
- Outdoors
- Weather resilience − rain, wind/snow loading
- Mobile
- Limitations on space / weight / power
- Technical riders
- Contractual basis
- Typical content
- Desired vs achievable/affordable − negotiation
- System sizing
- Number of microphones
- Speakers
- Amplifiers
- Mains power
- Mixers and multicores
- Mono versus stereo
- Speakers
- Assembly sequences
- Early decisions about locations
- Staffing factors
- Rack systems
- 19 inch format
- Vertical units
- Flight case systems (SKB etc.)
- Speaker location and orientation
- Audience orientation
- Horizontal plane
- Vertical plane
- Visual analysis
- Delayed feeds
- Mixer location
- Miking vocals
- Understanding requirements
- Height
- Distance (boom required?)
- Polar pattern & its consequences
- Sufficient cable, when mics are held or stands are moved
- Identification
- Needed when mics are held or stands are moved
- Colour of windshield/cable
- Coloured markings
- Speech
- Solo
- Performer's microphone technique
- Small group
- Choir
- Understanding requirements
- Miking instruments
- Guitar
- Piano
- Woodwind & brass
- Drums
- Max SPL
- Backline
- Monitor positioning
- Target listeners
- Avoiding feedback
- Minimising spill to audience
System Operation
- Rig checks
- Main
- Left / Right connection
- Crossovers
- Speaker management
- Left / Right balance
- Phase
- Monitors
- IEMs
- Line checks
- Mics
- DI
- Talkback etc.
- Main
- System tuning
- Measurement & analysis techniques
- Setting delays
- Time/distance vs listening position
- FOH
graphics
- Analytical, pink noise
- Audio test CDs
- Listening tests, familiar CDs
- Monitor graphics
- Ringing out
- Disapplication to FOH
- Sound-checks
- Dependence on time available in venue
- Dependence on band/assistant co-operation
- The solo principle and alternatives
- Setting mixer gain controls
- Input level nominal values
- Input level dynamics
- Individual/common metering
- Use of PFL
- Indicator LEDs
- Setting EQ
- Compensation for source deficiencies
- Source modification
- Consequences for fundamentals & harmonics
- Relation to use of graphic equalisers
- System gain structure
- Backline,
monitor and
FOH levels
- Appropriate overall sound levels
- Relative contributions
- Spill
- Setting pan controls
- Audience orientation
- Left / Right power balance
- Mono centre feeds (LCR)
- Listening and looking
- Critical listening
- Overall sound level awareness
- Source activity awareness
- Balance awareness
- Changes at source
- Problem awareness
- Maintaining concentration
- Spectral balance
- Playing media
- Computer-based, tapes, CDs, DVDs, DAT, mini disc, vinyl
- Preparation
- Checking machine operation
- Readiness − track cueing
- Cues for start/stop, fade-in/fade-out
- Dynamic range
- Tapes
- Tape oxide types & equalisation
- Noise reduction
- Head magnetisation
- Head azimuth
- Media damage, skipping
- Vinyl
- Rumble
- RIAA equalisation
Problem-Solving
- Too loud!
- Evaluating the critique
- Appropriate levels
- Degree of control − sources of sound
- Room acoustics
- Sound containment
- Lack of bass
- Lack of clarity
- Source deficiencies
- Microphone deficiencies
- Speaker deficiencies
- Speaker location, orientation & directivity
- Room acoustics
- Frequency discrimination
- Distortion
- Input overload
- Internal overload
- Output overload
- Dependence on load impedance
- Faults
- In equipment/cables/connectors
- Feedback
- Acoustic
- Magnetic
- Electrical
- Hum,
buzz & crosstalk
- Origin
- Missing earths
- Safety factors
- Earth loops
- Unwanted couplings
- Equipment design deficiencies
- The 'pin 1 problem'
- Hiss
- Noise floor
- Dynamic range
- Target SPL
- Interference
- Emission levels and immunity levels
- EMI (RF)
- Mains-borne
- Induction loops
- Equipment faults
Buying to a Budget
- Quality
- Sound quality
- Build quality
- Microphones
- Quality versus number
- Speakers
- Quality, size, number & power
- Mixers
- Assessing
the requirements
- Quality
- Number of channels
- Facilities
- Future-proofing
- Assessing
the requirements
Introduction to Recording
- Differences from live mixing
- Wide variations in listening environments
- Wide variations in playback equipment quality
- Critical / casual listeners
- Importance of good stereo image
- Increased importance of FX
- Track continuity
- Live mixdowns
- Multitracking
- Tape-based
- Hard drive based
- Punch-ins
- Track isolation
- Source leakage
- Monitoring spill-over
- Recording
microphones
- Applications
- Specialist types
- Specialist mic pre-amps
- Stereo
mic techniques
- CD mastering
- Compressed formats
for Web etc.
- Studio protocol & constraints
- Producers
- Band management
- Respect for studio environment
- Time is money
- The importance of prior planning
Back to:
- Basics
- The Nature of Sound
- Electrical Fundamentals
- Electrical Signals
- Microphones
- Speakers
- Amplifiers
- Signal Interconnections
- Effects
- Mixers
- Power Distribution
- Safety
- Care of Equipment
- System Assembly
- System Operation
- Problem-Solving
- Buying to a Budget
- Introduction to Recording
© 2006-2020 Mark Phillips
This page last updated 16-Mar-2020.