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TV News Reporting and Production MCM 516

LESSON 12

LIGHT AND AUDIO

Types of cameras

According to utility there are different types of cameras.

Handy camera

ENG camera

Full facility camera

Digital camera

XD camera

Beta camera

Models in use

PD 150

PD 170

D 350

D 390

D 250 P

D 35 P

16 MM

35 MM

70 MM

Types of tapes/disks

Video

VTR

U-matic

Beta

DVC Pro

DV cam

Mini DV

VHS

VCD

DVD

Audio

Magnetic tape

DAT

Importance of sound in TV

Although TV is a visual medium still the there is no video suitable for telecast without good audio.

There are dialogues, music, original or wild sound; all make a package for a complete telecast.

Use of microphone

Perhaps the best way to emphasize the importance of microphone is to say that without it audio in media

would not exist so every thing for a broadcast or telecast starts with a microphone.

The microphone is a transducer that's converts acoustic or sound energy in to electric energy. This is the

basic function of a microphone. There are different types of microphones having special capabilities

according to varied aesthetic demands of recordings and productions.

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For example, in television if a microphone is in the shot, it should be presentable but should not call

attention to itself.

For outdoor productions a microphone must be resistant to the wind sound. When distance is a factor, a

microphone must isolate the sound source and still provide acceptable quality of audio.

The special requirements make microphone selection a critical and ever present creative challenge.

When you choose a microphone, you should know four things.

What type it is?

What are its directional characteristics?

What does it sound like?

What it looks like?

Types of microphones

According to technique

Moving coil/dynamic

Ribbon

Capacitor/condenser

According to direction

Omni or Multi-directional (picking sound all around)

Bi-directional (Front and rear)

Uni-directional (from front only)

According to usage

Neck microphone

Hand microphone

Cordless neck microphone

Cordless hand microphone

Cable neck microphone

Cable hand microphone

Boom handy (outdoor)

Boom on tripod (indoor)

According to programme

Drama

Talk show

Music

Magazine show

Documentary

Television Sound: The Basics

Until rather recently, far more attention was paid to video in television than to audio. "Good sound" was

when you could make out what was being said; "bad sound" was when you couldn't.

This has changed. With the advent of stereo and 5.1 surround-sound, audiences have much greater

expectations.

Before we can discuss some of the basic audio production concepts, sound itself must be

understood. Sound has two basic characteristics that must be controlled: loudness and

frequency.

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Loudness

Although sound loudness is commonly measured in decibels (dBs), that term actually refers to two

different things.

First is DBSPL (for sound pressure loudness), which is a measure of acoustic power. These are sounds

we can directly hear with our ears.

These decibels go to and beyond 135, which is considered the threshold of pain and, by the way, the

point at which permanent ear damage can occur. If your ears "ring" after being around a loud sound, this

should be a warning sign that you have crossed the threshold of potential hearing damage. (The damage,

which is irreversible, often goes unnoticed, which probably explains why the average 50-year-old in

some countries has better hearing.)

Musicians who must be around high-level sound use musician's plugs -- special earplugs that attenuate

sound level without distorting the frequency range.

Various sound pressure decibel levels (in dBSPL's) are shown here.

Sound

dBs

Jet Aircraft Taking Off

140-150

Rock Concert / Gunshots

135-140

Jackhammer at 15 meters / Subway 85-90

Average City Street / Restaurant

70- 75

Quiet Conversation / Phone Dial

60-80

Tone

Office Environment

Whisper at 3 meters (10 feet)

"Silent" TV Studio

The second use of the term decibel, dBm (for the milliwatt reference level) is a unit of electrical power.

These decibels are displayed on loudness meters. In audio production we are primarily interested in

dBm, which represents levels of electrical power going through various pieces of audio equipment.

Two types of VU meters for measuring the loudness of sound are in wide use: the digital type and the

analog type. Below are three examples of digital meters. The scale on the left side of the large drawing

shows modulation percent (percentage of a maximum signal), and the scale on the right is in dB's.

Contrary to what logic might dictate, 0dBm (generally just designated 0dB on a VU meter) is not "zero

sound" but, in a sense, the opposite, the maximum desirable sound level. (Granted, that's a bit confusing,

but, then again, we didn't make up this system!)

The 0dB point on the meter is just a reference point. Therefore, it's possible to have a sound level on the

meter that registers in negative dBs, just as it's possible to have a temperature of -10 degrees Centigrade

or Fahrenheit.

These animated versions above illustrate how digital meters respond to sounds.

The VU meter below on the right is the traditional analog meter that has been around in one form or

another since the dawn of radio.

Although easy to read, most versions do not accurately respond to short bursts of loud sound.

The dB level going through audio equipment must be carefully controlled. If the signal is allowed to

pass through equipment at too low a level, noise can be introduced when the level is later increased to

normal amplitude (audio level).

If the level is too high (significantly above 0 dB or into the red areas on the VU meter) distortion will

result -- especially with digital audio. To ensure audio quality, you must pay constant attention to

maintaining proper audio levels.

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The animated meter shown here indicates a sound level that is a bit too high. Ideally, the needle should

not go deeply into the red area this often.

Frequency

Frequency relates to the basic pitch of a sound -- how high or low it is. A frequency of 20 Hz would

sound like an extremely low-pitched note on a pipe organ -- almost a rumble. At the other end of the

scale, 20,000 Hz would be the highest pitched sound that most people can perceive, even higher than the

highest note on a violin or piccolo.

Frequency is measured in Hertz (Hz) or cycles per second (CPS). A person with exceptionally good

hearing will be able to hear sounds from 20-20,000 Hz. (Generally, women can hear higher frequencies

than men.)

Since both ends of the 20-20,000Hz range represent rather extreme limits, the more common range used

for television production is from 50 to 15,000 Hz. Although it doesn't quite cover the full range that can

be perceived by people with good hearing, this range does cover almost all naturally occurring sounds.

The Frequency-Loudness Relationship

Even though sounds of different frequencies may technically be equal in loudness (register the same on

a VU meter), human hearing does not perceive them as being of equal strength.

The red line on the graph (roughly) shows the frequency response of the human ear to different

frequencies.

Because of the reduced sensitivity of the ear to both high and low frequencies, these sounds must be

louder to be perceived as being equal to other frequencies.

You'll note that a good-quality microphone (the green line) is relatively "flat" in the all-important 50-

15,000 Hz. range.

Listening Conditions

Equipment and listening conditions also greatly affect how different frequencies will be perceived. To

compensate for some of these problems, we can adjust bass and treble controls of playback equipment.

More sophisticated equipment will include a graphic equalizer, which goes a step further and allows

specific bands of frequencies to be individually adjusted for loudness.

A graphic equalizer may be necessary to match audio segments recorded under different conditions, or

simply to customize audio playback to the acoustics of a specific listening area.

Note that the graphic equalizer shown here can control nine specific frequency areas.

Any piece of audio equipment -- microphone, amplifier, recorder, or audio speaker -- can adversely

affect the fidelity of sound. However, it's the microphone (the initial device that transducer sound waves

into electrical energy) and the audio speaker (the device that changes electrical energy back into sound

waves) that represent the weakest links in audio quality.

To some degree it's possible to use graphic equalizers and other audio equipment to "clean up" the

frequency response of a poor microphone. However, even the most sophisticated audio techniques can't

work miracles. Thus, the better the original audio signal, the better the final product will be.

Room Acoustics

Sound, both as it's recorded and played back, is more affected by the acoustics of a room or studio than

most people realize.

In an effort to create totally soundproof studios, early radio stations used to use thick carpets on the

floors and heavy soundproofing on the walls.

Although possibly successful as soundproofing, the result was a lifeless and dead effect that we're not

used to hearing in a normal environment, such as our living rooms.

Two types of soundproofing material are shown on the left.

At the other extreme is a room with a tile floor and hard, parallel walls that reflect sound. The result is

reverberation (a slight echo) that interferes with the intelligibility of speech.

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The ideal room for recording or listening to sound has just enough reverberation to sound realistic,

similar to your living room possibly, but not enough to reduce the intelligibility of speech.

Microphones

Dynamic Microphones

The dynamic mic (also called a moving-coil microphone) is considered the most rugged professional

microphone.

This type of mic is a good choice for electronic newsgathering (ENG) work, where a wide variety of

difficult conditions are regularly encountered (such as this ENG report on a fire).

In a dynamic microphone sound waves hit a diaphragm attached to a coil of fine wire. The coil is

suspended in the magnetic field of a permanent magnet.

When sound waves hit the diaphragm they move the coil of wire within the magnetic field. As a result, a

small electrical current is generated that corresponds to the original sound waves. This signal must be

amplified thousands of times.

When small size, optimum sensitivity, and the best quality are all prime considerations, another type of

mic, the condenser mic, is often preferred.

Condenser/Capacitor Microphones

Condenser microphones (also called capacitor or electret condenser mics) are capable of top-notch

audio quality.

As shown on the left, they can be made so small that they are almost invisible. (But, the smaller they

are, the more expensive they tend to be!)

Condenser mics aren't as rugged as dynamic mics, and problems can result when they are used in

adverse weather conditions.

Condenser mics work on the principle that governs an electric condenser or capacitor. An ultra-thin

metal diaphragm is stretched tightly above a piece of flat metal or ceramic. In most condenser mics a

power source maintains an electrical charge between the elements.

Sound waves hitting the diaphragm, cause fluctuations in an electrical charge, which then must be

greatly amplified by a preamplifier (pre-amp). The pre-amp can be located within the microphone

housing or in an outboard electronic pack. Although most pre-amps output an analog signal, some of the

newer models immediately convert the output to digital.

Because they require a pre-amp, this means that, unlike the dynamic mics discussed earlier, most

condenser mics require a source of power, either from an AC (standard Alternating Current) electrical

power supply or from batteries.

An AC power supply for a condenser mic is sometimes built into an audio mixer or audio board. This is

referred to as a phantom power supply. When this type of power supply is used, the mic cord ends up

serving two functions: it delivers the signal from the mic to the mixer and it carries power from the

mixer to the pre-amp of the condenser mic.

Of course, using batteries to power the pre-amp of the condenser mic is more convenient -- you don't

have to use a special mixer or audio board connected to an electrical power source.

But, battery-powered condenser mics introduce a problem of their own: at the end of their life cycle the

batteries can go out without warning.

To get around any unexpected problems, especially on important productions, two miniature condenser

mics are often used together. If one mic goes out, the other can immediately be switched on. This

double microphone technique is called dual redundancy, a term that is somewhat redundant in itself.

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Summary of Dynamic and Condenser Mic Pros and Cons

Dynamic Mic Advantages

Condenser Mic Advantages

Rugged

More Sensitive

Lower Cost

Better Audio Quality

No Power Required

Can Be Extremely Small

Dynamic Mic Disadvantages

Condenser Mic Disadvantages

Lower Sensitivity and Power Output Higher self-noise

Larger and Heavier

More Fragile

Slower Response Time

More Expensive

Not the Best Choice for Maximum Prone to Weather Problems and RF

Audio Quality

Interference

Ribbon Mics

Except possibly for an announce booth, ribbon mics are seldom used in TV production.

Although they can impart a deep, resonant "coloring" to sound, they are fragile and highly sensitive to

moving air. This precludes their use outside the studio and on most booms, which covers most TV

production applications. Ribbon mics were primary used in radio studios.

Boundary Effect Mics

PZ (also called PZM) stands for sound pressure microphone for standard video work, which comes

under the heading of a boundary effect microphone. This mic relies entirely on reflected sound.

In specific situations, such as when placed on a tabletop, a PZ mic will provide a pickup that's superior

to that of other types of mics.

Contact Mics

As the name suggests, contact mics pick up sound by being in direct physical contact with the sound

source. These mics are generally mounted on musical instruments, such as the surface of an acoustic

bass, the sounding board of a piano, or near the bridge of a violin.

Contact mics have the advantage of being able to eliminate interfering external sounds and not being

influenced by sound reflections from nearby objects. Their flat sides distinguish them in appearance

from small personal mics.

Directional Characteristics

In an earlier module we talked about the angle of view of lenses -- the area that a lens "sees."

Microphones have a similar attribute: their directional characteristics, or, you might say, the angle of

view that they "hear."

In microphones there are three basic directional categories:

omni directional

bi-directional

unidirectional

Omni directional Mics

Omni directional mics (also called non-directional mics) are (more or less) equally sensitive to sounds

coming from all directions.

Although this attribute would have advantages in radio where several people could stand or be seated

around a single microphone, in video production it's almost always more desirable to use some form of

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directional mic. For one thing, this will reduce or eliminate unwanted sounds (behind-the-camera noise,

ambient on-location noise, etc.) while maximizing sound coming from talent.

Bi-directional Mics

In a bi-directional sensitivity pattern (bipolar pattern) the mic is primarily responsive to sounds from

two directions. Note drawing above.

Although commonly used in radio interviews for people sitting across from each other at a table, until

the advent of stereo, bi-directional (also called figure eight) sensitivity patterns had limited use in

television. We'll get into stereo and the need for this type of directional pattern in a later module.

Unidirectional Mics

The term unidirectional simply refers to a general classification of mics that are sensitive to sounds

coming primarily from one direction.

There are four subdivisions in this category -- each being a bit more directional:

Cardioids

Super cardioids

Hyper cardioids

Parabolic

Although these terms may sound as if they belong in a medical textbook, they simply refer to how

narrow the mic's pickup pattern ("angle of view") is.

Cardioids

The cardioid (pronounced car-dee-oid) pattern is named after a sensitivity pattern that vaguely

resembles a heart shape. The drawing here is a highly simplified depiction of three directional patterns.

Mics using a cardioid pattern are sensitive to sounds over a wide range in front of the mic, but relatively

insensitive to sounds coming from behind the mic.

Although this pattern might be useful for picking up a choir in a studio, the width of a cardioid pattern is

too great for most TV applications. When placed two or more meters (7 or more feet) from a speaker, it

tends to pick up unwanted, surrounding sound, including reverberation from walls.

Super-cardioids

The super-cardioid is even more directional than the cardioid sensitivity pattern. Whereas the cardioid

has about a 180-degree angle of acceptance, the super-cardioid has about 160-degrees of coverage.

When this type of mic is pointed toward a sound source, interfering (off-axis) sounds tend to be

rejected.

This polar pattern is similar to that of our ears as we turn our head toward a sound we want to hear and

try to ignore interfering sounds.

Hyper-cardioid and Lobar

Even more directional are the hyper-cardioid and lobar patterns with 140-degrees of coverage. Because

off-axis sounds will be largely rejected, they have to be accurately pointed toward sound sources. Some

highly directional shotgun mics (below) are included in the hyper-cardioid category.

Shotgun Mics

So called shotgun mics with their hyper-cardioid or narrower angles of acceptance are one of the most

widely used types of mics for on-location video work. Since they are quite directional, they provide

good pickup when used at a distance of 2 to 4 meters (7-13 feet) from the talent. Like other types of

directional microphones, they tend to reject sound that would interfere with the on-camera talent.

Parabolic Mics

Parabolic mics represent the most highly directional type of mic application. This category refers more

to how a microphone is used than to a type of mic or its basic directional pattern.

It's the parabolic reflector that creates the polar pattern for this mic, not the mic itself. In fact, the mic

used in the focus point (center) of the parabola can be any general cardioid or super-cardioid mic.

The parabolic reflector can be from 30 cm to 1 meter (1 to 3 feet) in diameter.

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Because of the parabolic shape of the reflector, all sound along a very narrow angle of acceptance will

be directed into the microphone in the center.

Parabolic microphones can pick up sound at distances of more than 60 meters (200 or more feet). These

mics are not a practical choice for general field production work, but they are often used in sports.

For parabolic mics, or any type of directional mic used on location, the person controlling the mic

should always be wearing a good set of padded earphones connected to the mic's output, especially if

subjects are moving.

A slight error in aiming a highly directional mic can make a big difference in audio quality.

Using Off-Camera Microphones

Although it may be appropriate to use handheld, lav, or RF mics for interviews, there are instances in

television production when it's desirable to use an unseen microphone -- generally one that's outside of

the camera's field of view.

Examples would be:

because seeing a mic wouldn't be appropriate, as in the case of a dramatic production

when mic cords would restrict the movement of talent, such as in a dance number

when there are too many people in the scene to use multiple personal, handheld or RF

mics, such as with a choir

Because of their nondirectional nature, omni directional or simple cardioid-patterned microphones used

at a distance of 1½ meters (five or six or feet) or more quickly start picking up extraneous sounds.

Depending on the acoustics of the location, this can also cause the audio to sound hollow and off-mic.

Consequently, only microphones with a super cardioid or narrower pattern should be used as off-camera

mics.

Just as the eye sees selectively and may not notice a coat rack "growing out of" someone's head in a

scene, the ears hear selectively and may not notice an annoying reverberation in a room, which, when

picked up by a mic, can render speech difficult to understand.

Microphone Booms

In the studio the simple fish-pole moves into the much more sophisticated category of boom mic.

Microphone booms range from a small giraffe (basically a fish-pole mounted on a tripod) to a large

perambulator boom (that weighs several hundred pounds, takes two people to operate, and can extend

the mic over the set from a distance of 100 meters (more than 30 feet).

The largest booms have a hydraulically controlled central platform where operators sit and watch the

scene on an attached TV monitor while controlling such things as the

left or right movement (swing) of the boom arm

boom extension (reach of the arm)

left to right panning of the attached microphone

vertical tilt of the microphone

Hanging Microphones

Sometimes you can get by without a boom mic, especially if the talent is confined to a limited area.

For example a mic can be suspended over a performance area by tying it to a grid pipe or fixture just

above the top of the widest camera shot. The disadvantage of this approach, of course, is that the mic

can't be moved during the production.

Both boom mics and suspended microphones should be checked with the studio lights turned on to

make sure they do not create shadows on backgrounds or sets.

Hidden Microphones

It's sometimes possible to hide microphones close to where the on-camera talent will be seated or

standing. This will eliminate both the need for personal or handheld mics and the problems that mic

cords can introduce.

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Microphones are sometimes taped to the back of a prop or even hidden in a table decoration, such as the

vase of flowers shown here.

When placing mics, keep in mind the proximity effect discussed in an earlier module. You may find

during an editing session that the audio from different mics used at different distances will not "cut

together" (edit together) without annoying changes in quality.

Sometimes several mics must be used on a set at the same time. In this case each mic not being used at a

particular moment should be turned down or switched off. This also reduces total ambient sound.

Phase Cancellation

Phase cancellation, which results in low-level and hollow-sounding audio, occurs when two or more

mics pick up sound from the same audio source.

Because the sounds arrive at the mic at slightly different times, they end up being out of phase and to

various degrees they can cancel each other out.

When multiple mics are used on a set there are four things you can do to reduce or eliminate the

resulting phase cancellation:

place mics as close as possible to sound sources

use directional mics

turn down mics any time they are not needed

Carefully check and vary distances between the sound sources and multiple mics to reduce

or eliminate any cancellation effect (A speaker's mic should be placed at one-third or less the

distance of the next nearest mic.)