Sound waves travel through air and are caused by vibrating objects. They have properties of frequency, amplitude, and phase. The human ear is most sensitive to mid-range frequencies and less so for high and low frequencies. There are different types of microphones including dynamic, condenser, and directional microphones that are used for different applications like interviews, field recording, and studio work.

1. Introduction to Sound
Sound and light both travel as waves.
The properties of these waves differ quite
considerably.
Sound waves travel a million times slower than
light waves.
They have wavelengths between 1 centimeter
and 10 meters, and will easily diffract round
corners. Light waves have much smaller
wavelengths, and only diffract through very
small holes.
This difference is the reason why you can often
hear things that you cannot see.

2. What Is Sound?
All sounds are vibrations traveling through the air as sound
waves. Sound waves are caused by the vibrations of objects
and radiate outward from their source in all directions. A
vibrating object compresses the surrounding air molecules
(squeezing them closer together) and then rarefies them (pulling
them farther apart). Although the fluctuations in air pressure
travel outward from the object, the air molecules themselves
stay in the same average position. As sound travels, it reflects
off objects in its path, creating further disturbances in the
surrounding air. When these changes in air pressure vibrate
your eardrum, nerve signals are sent to your brain and are
interpreted as sound.

3. Fundamentals of a Sound Wave
The simplest kind of sound wave is a sine wave. Pure
sine waves rarely exist in the natural world, but they are
a useful place to start because all other sounds can be
broken down into combinations of sine waves. A sine
wave clearly demonstrates the three fundamental
characteristics of a sound wave: frequency, amplitude,
and phase.

4. TV Sound
sound loudness is commonly measured in
decibels (dBs )
Sound dBs
Jet Aircraft Taking Off 140-150
Rock Concert / Gunshots 135-140
Average City Street / Restaurant 70- 75
Quiet Conversation / Phone Dial
Tone
60-80
Office Environment 45
Whisper at 3 meters (10 feet) 30
"Silent" TV Studio 20

5. Two types of VU meters for measuring the loudness
of sound are in wide use
The digital type and the analog type.

6. Frequency
Frequency relates to the basic pitch
of a sound -- how high or low it is
Frequency is measured in Hertz (Hz)
or cycles per second (CPS).

7. The Frequency-Loudness
Relationship
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.

8. Major Microphone Designs
There are six common microphone designs:hand held - the type
held by on-camera talent or used for on-location interviews
personal mic (lavaliere / clip-on mic) - Whether hung from a cord
around the neck (lavaliere) or clipped to clothing, these are all
referred to as personal mics.
shotgun - used for on-location production to pick up sounds a
moderate distance from the camera
boundary effect microphone - also called PZ or PZM mics These
rely primarily on reflected sounds from a hard surface such as a
tabletop
contact mics - which pick up sound by being in direct physical
contact with the sound source. These mics are generally mounted
on musical instruments.
studio microphones - the largest category of microphone. These
include a number of application designs that we'll discuss.

9. Dynamic Microphones
Dynamic Microphones
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).

10. Condenser/Capacitor Microphones
Condenser microphones (also called capacitor or electret
condenser mics) are capable of top-notch audio quality.
Condenser mics aren't as rugged as dynamic mics, and
problems can result when they are used in adverse weather
conditions.

11. 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
Audio Quality
Prone to Weather Problems and RF
Interference

12. Ribbon Mics
Except possibly for an announce booth (shown here), 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 produc

13. Boundary Effect Mics
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.

14. Directional Characteristics
In microphones there are three basic directional categories:
omnidirectional
bi-directional
unidirectional

15. Unidirectional Mics
There are four subdivisions in this category -- each being a bit
more directional:
cardioid
supercardioid
hypercardioid
parabolic

16. Parabolic Mics
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.

17. Handheld Microphones
Handheld mics are often dynamic mics because they are
good at handling momentary sound overloads. Although
they may be called "handheld," the term is a bit of a
misnomer, because this type of mic can be mounted on a
microphone stand.

18. Personal Microphones
Personal mics are either hung from a cord around the
neck (a lavaliere or lav mic) or clipped to clothing (a
clip-on mic).
This type of mic can be either a condenser or
dynamic mic.