Transcript how microphones hear

HOW MICROPHONES HEAR
Microphone types and how they hear
Choosing the most appropriate
microphone, or mic, and operating it for
optimal sound pickup requires that you
know the 3 basic types of sound
generating elements, their pick up
patterns, and some additional
microphone features.
SOUND GENERATING ELEMENTS
All microphones transduce(convert) sound waves into
electric energy, which is amplified and reconverted
into sound waves by the loudspeaker. The initial
conversion is accomplished by the microphone’s
generating element.
There are 3 major types of sound converting systems,
which are used to classify microphones:
a) Dynamic
b) Condenser
c) ribbon
DYNAMIC MICROPHONES
• They are the most rugged.
• Also called moving-coil microphones, they can tolerate
reasonably well the rough handling that tv mics usually
receive.
• They can be worked close to the sound source and withstand
high sound levels without damage to the microphone or
excessive input overload (distortion of very high volume
sounds).
• They can withstand fairly extreme temperatures.
• They are an ideal outdoor mic.
CONDENSER MICROPHONES
• Are much more sensitive to physical shock, temperature change, and input
overload.
• They usually produce higher-quality sound when used at greater distances
from the sound source.
• They have an in built preamplifier. It strengthens the sound signal so that
it does not get lost on the way to the camcorder, mixer, or console.
• The power supply for condenser mics is usually a battery. Always keep
extra batteries in hand especially when on ENG/EFP.
• Condenser mics can be powered through voltage supplied by the audio
console or mixer through the audio cable. This method of supplying power
to the mic’s preamp is called phantom power.
RIBBON MICROPHONES
• Similar in sensitivity and quality to condenser
mics.
• They produce a warmer sound and are
preferred by singers.
• They are strictly for indoor use.
PICK UP PATTERNS
Whereas some microphones, like our ears, hear sounds from all directions
almost equally well, others hear sound better when they come from a
specific direction. The territory within which a microphone can hear
equally well is called its pickup pattern. Its two dimensional representation
is called the polar pattern.
In television production you need to use both omnidirectional and
unidirectional microphones, depending on what and how you want to
hear. The omnidirectional microphone hears sounds from all directions
more or less equally well.
The unidirectional microphone hears better in one direction-the front of the
mic-than from its sides or back. Because the polar patterns of
unidirectional microphones are roughly heart-shaped, they are called
cardioids.
Which type of microphone you use depends primarily on the
production situation and the sound quality required. If you are
doing a stand up report (standing in front of the actual scene) on
conditions at the uhuru park, you would want a rugged,
omidirectional mic that not only favours speech but also picks up
some of the campaign sounds for authenticity.
If, on the other hand, you are video recording a singer in the
studio, you should probably choose a high quality mic with a more
directional cardioid pick up pattern.
To record an intimate conversation between two soap opera
actors, a hypercardioid shotgun mic is probably best. The shotgun
mic can pick up their conversation from relatively far away without
losing sound presence(the closeness of the sound) while ignoring
to a large extent many of the other studio noises, such as people
and cameras moving about, the humming of lights, or the rumble
of air conditioning.
MICROPHONE FEATURES
Microphones that are held close to the mouth have a built in pop filter, which
eliminates the sudden breath pops that might occur when someone
speaks directly into the mic.
When used outside, all types of microphones are susceptible to wind, which
they reproduce as low rumbling noises. To reduce wind noise, put a wind
screen made of acoustic foam rubber over the mic. To cut the wind noise
even more, you need to pull a windsock, or wind jammer, over the
windscreen. The windjammer is made from a synthetic material that
resembles a mop. Remember however that whatever you use, some wind
noise cannot totally be eliminated. The only way is to shoot when there is
no wind.
You can however use filters in postproduction that can reduce or eliminate
some wind noise, or you can cover it up with sound effects or music.
MICROPHONE TYPES BY HOW THEY ARE
USED
•
Some microphones are designed and used primarily for sound sources that are moving,
whereas others are used for stationary sound sources.
• When grouped according to how they are used, there are mobile and stationary
microphones. Of course, any of the mobile mics can be used in a stationary position,
and the stationary mics can be moved about if the production situation so requires.
Mobile mics include:
 Lavalier
 Hand
 Boom
 Headset and
 Wireless mics.
The stationary microphones include:
 Desk
 Stand
 Hanging
 Hidden and
 Long distance mics.