Tv sound..
Transcript of Tv sound..
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.
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.
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.
TV Soundsound 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
Two types of VU meters for measuring the loudness
of sound are in wide use
The digital type and the analog type.
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).
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.
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.
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).
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.
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
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
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.
Directional Characteristics
In microphones there are three basic directional categories:
omnidirectional
bi-directional
unidirectional
Unidirectional Mics
There are four subdivisions in this category -- each being a bit more directional:
cardioid
supercardioid
hypercardioid
parabolic
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.
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.