SOUND CHAIN

EQUIPMENT:
Mechanical effects:
These are PROPS department
Mechanically created sounds and noises.
E.G.: Door slams and knocks, Bells, gongs, other musical instruments,
 Thunder sheets, thunder carts and thunder runs	
 Slapsticks, etc. Gunshots    Still viable for percussive sounds.

HOWEVER:
Most effects are Electrical in some fashion.
More dependable
More predictable
More controllable
Usually easier
Sound involves a chain of equipment, Small to Large.

Basic Path:
Small signal:  -->  Med. signal:    -->   Large signal:
Sources -->  Control & manipulation  --> Power amps/ Speakers


Beginning with:

Sources
Transducers:
	* Microphones:  sound pressure to electricity.
	* Phonograph:  wobbly grooves in cylinder or disk into electricity.
	* Tape:  magnetic patterns to electricity.
	* CD-ROM:  optical inferference patterns in reflective media into electricity. etc.
	* Mini-disk, hard disk: digital file on magnetic media translated to electricity
Sources must be amplified.
	* Sound inherantly a low level energy effect.
	* Originating transducers very small energy levels.
	* Translating from one form to another inefficient.
Preamps:
Transducers produce very tiny voltages. Typical levels may be around .001 volts    
Sound pressure not very powerful,    Transducers very inefficient.
Pre-amps raise sources to a standard level.

LINE LEVEL 2 standards:
   •Home: approx. 1(-) volt
   •Professional: approx. 1(+) volt, a little hotter.

Line level a good level to work with.
   •Large enough to manipulate w/o need for very robust
     power equipment.
   •Better Signal-to-Noise ratio at line level.

S/N ratio:  Amount of Signal (desired sound) to Noise (unwanted or random sound).
   •Where signal small, small noise relatively large.
   •Noise early in chain is amplified throughout sound path.

Different devices need different pre-amps.
However
Output stages are all in same range.

Next stage in chain:

CONTROL AND MANIPULATION
Line level devices
	* Mixer
	* EQ
	* Processing and effects
At this stage: most active adjustment occurs.

AMPLIFIERS, also called POWER AMPS
   (to distinguish from Pre-amps)
All amps boost smaller signal to a proportionally larger one.
	* Pre-amps raise to Line level
	* Power amps raise to Speaker level.

Final step:

SPEAKERS
Transducers that turn electricity into Sound Pressure.
Summary:

The Sound Path:
Sources --> Preamp --> EQ --> --> Mixer --> Power amps --> Speakers


NATURE OF SOUND

Sound:  mechanical movement of sound energy through a medium, e.g. air.

Sound travels through a medium; no sound in vacuum.
   Denser the medium, the faster the sound.
     1000 ft./sec. @ sea level

Sound travels in waves
   Our ears sensitive to freq. of approx.
      Pitch: 20 Hz to over 20,000 Hz.
Like eyes, Ears are approx. logarithmic.
	* Very sensitive to low volumn sound, tends to attenuate very loud sounds.
	* Doubling apparent gain of low volumn sound much less energetic than 
        doubling loud sound.

AMPLITUDE: loudness

Sound envelope: amplitude plotted over time.

Ears somewhat more prone to permanent damage from overexposure than eyes.
	* Long term exposure to sound can cause damage.
	* Eye deterioration more related to age.
     Acute exposure can damage either.

Processes different between Lighting and Sound.
	* Light: Production
     Create and manipulate light.
	* Sound: RE-production
     Recording and recreating a sound effect.

Sound is a mechanical phrenomenon
   To record and reproduce, Transducers are required.
   Transducers change energy from one form to another,
     e.g. usually to or from electricity.

Transducers:
   Mics: sound to electricity.
   Phonographs: wobbles in a groove to electricity.
   Tape and magnetic disks:  mag. patterns to electricity.
   Optical media: digital patterns to analog electricity.
   Speakers:  electricity back to sound.

MEASURING SOUND

To discuss sound, we need a unit of measure.
   The DeciBel

Basic measure:  the deciBel.  1/10th of a Bel.
Bel (as in Alexander G. Bell) = the amount of increase required to double apparent 
intensity of sound.
   Therefore:  doubling gain means increasing 1 Bel, or 10 dB.

Hearing is logarithmic, so it takes 3 dB just to make a noticeable change.

Important:  dB is a ratio;  it is always expressed compared to something else.
   dB w/o reference is meaningless.

dB can be expressed in comparison to another level, or to one of several 
standards, depending on what is being compared.    
SPL (sound pressure level): 0 dB =threshold of hearing
   Power in Watts: 0 dBm =1 milliwatt (.001 w)
   Volts: 0 dBu =.775 v. into 600 ohms
     (tends to be the same as dBm into 600 ohms,
     but is always .775 v.)
   Volts: 0 dBV =1 v. regardless of impedance.
     Used for high impedance circuits, which are voltage sensitive,
     typical of consumer electronics.

The Purpose of Sound
:
First and Foremost:  reinforce the play, just as lighting, scenery, costumes.
   As scenery & lighting add physical and emotional space to show,
   Sound adds aural texture, the sound environment
   Additional purpose:  making actors audible.

Sound has two tasks:  Effects and Reinforcement.

EFFECTS:
   Non-actor originating sounds put into show.  Includes:
   "Sound Effects"-  noise on or off stage
   "Music"-  background, incidental, and internal
   Pre-, Post- or Intermission Music, to "set the mood"

REINFORCEMENT:
   Amplifying the actor, esp. his voice.
   May include effects added to voice, but this is
     still reinforcement.

Effects involve producing, recording, and reproducing sounds.
Reinforcement usually involves mics to capture live sound for amplification.