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Physics of Sound. Sound is a series of atmospheric pressure waves produced by a vibration The height (amplitude) corresponds to loudness and the wavelength to frequency. Physics of Sound. Loudness is determined by the amount of pressure produced by a wave measured in decibels

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physics of sound
Physics of Sound
  • Sound is a series of atmospheric pressure waves produced by a vibration
  • The height (amplitude) corresponds to loudness and the wavelength to frequency
physics of sound2
Physics of Sound
  • Loudness is determined by the amount of pressure produced by a wave measured in decibels
  • An increase of 10 decibels equals twice the volume
  • Threshold of hearing is the softest audible sound, threshold of pain is 130dB. A normal conversation is 65 dB above the threshold of hearing
  • Dynamic range: highest to lowest point
physics of sound3
Physics of Sound
  • Frequency determines the pitch of a sound
  • The cycles of waves are measured in hertz (Hz) or cycles per second. Western instruments use 440 Hz as a standard for the pitch A
  • Doubling the frequency = octave
  • Ear is more sensitive to midrange frequencies than to low or high frequencies
physics of sound4
Physics of Sound
  • Frequency response refers to how an audio system or microphone responds to various frequencies
  • Good audio recorders are capable of flat or equal response to all frequencies, consumer camera mics may not be
  • Using equalizers to change the frequency response for given ranges of any sound changes the nature of that sound
sound equipment
Sound Equipment
  • Camcorder mics work well for short distances, the inverted square rule
  • Professional camcorders give you audio level control, consumer ones often don’t
  • Using mics outside the camcorder offers more flexibility in shot choice and the chance to have a master soundtrack
sound equipment6
Sound Equipment
  • Microphone types

- dynamic or moving coil are quite rugged, resistant to hand noise, require no battery

- condenser mics are more sensitive and require a power source

- electret condenser mics have a permanently charged capacitor and may be small and require no power supply

sound equipment7
Sound Equipment
  • Microphone directionality

- omni-directional mics respond equally to sounds from any direction

- cardioid mics are most sensitive to sounds comimg from the front, less to the sides, and least to the back

- super-cardioid mics are insensitive to sounds not coming from the front

sound equipment8
Sound Equipment
  • Microphone directionality

- polar diagrams show sensitivity from above

- hyper/super cardiod (shotgun) mics do not magnify sound, but exclude it

sound equipment9
Sound Equipment
  • Lavalier mics or lapel mics

- useful for recording individuals in noisy environments

- the resonation of sound in the chest can make the voice sound low and unnatural

sound equipment10
Sound Equipment
  • Stereo Mics

- X-Y configurations are usually built into camcorders

  • uses two cardioid mics each pointed 45˚ to the side
sound equipment11
Sound Equipment
  • Stereo mics

- M-S (mid-side) mics uses a cardioid mic facing forward and a figure 8 mike for the sides

- useful for mixing down if you have good editing equipment

recording techniques
Recording Techniques !
  • Controlling microphone noise

- wind across the microphone creates loud rumbles, crackle, and pops

- wind screens and blocking objects help

- handling of the microphone or touching of the camera and vibrations from the tripod can also create noise

recording techniques13
Recording Techniques
  • Microphone distance

- ideally 1-3 feet, camcorder mics record speech accurately up to about 5 or six feet

- too close, breathing, s sounds, pops, bass tone proximity effect

- to far away means more ambience sound

- compromised sound perspective can be adjusted with reverb

recording technique
Recording Technique !
  • Digital recording levels and overmodulation

- overmodulated (too loud) analog sounds becomes crackly, with digital recording, it is distorted and clipped off

- digital recordings should be concerned more with recording too loud, though camcorders don’t overmodulate easily

recording technique15
Recording Technique
  • Camcorders and Automatic Level Control

- ALC or automatic gain control works by adjusting the recording level based on the signal it receives

- test the sound signal in your environment to see of any radical level changes take place

recording technique16
Recording Technique
  • Ambient sound

- the background sound in any production can be minimized by turning off appliances, choosing quiet times and spaces, or using sound blankets

- record about a minute of room tone at every location

- ambient sound should be consistent from one shot to the next

recording technique17
Recording Technique !
  • Noisy locations

- get the mic as close to the source as possible

- use lavalier mics

- use directional mics like shotgun mics and position your subject outside of a major noise source

- ideal to have two sound sources, subject and background

recording technique18
Recording Technique !
  • Acoustic space

- live spaces reflect sound and cause echos, such as empty rooms with hard smooth walls and floors

- dead spaces absorb the sound, such as carpeted rooms with lots of furniture and irregular walls.

- outdoor spaces can be dead because they have no reflecting surfaces

recording technique19
Recording Technique
  • Controlling reflected sound

- a live room can produce a muddled reverberating sound

- you can minimize reverberation:

- close directional

- deaden walls and floor with curtains/blankets

- you may use reflected sound to your advantage

recording techniques20
Recording Techniques
  • Position mics to avoid reflected sound from the camera
recording technique21
Recording Technique
  • Narration

- voice over tracks are ideally recorded in sound proof environments. A make shift one can be made out of sound blankets

- off screen narration gives the video a sense of omniscience, objectivity, and predestination

recording technique22
Recording Technique !
  • Capturing sound effects

- sounds directly captured from the environment

- sounds from a sound library or from the internet

- foley sounds

sound s impact on image
Sound’s Impact on Image
  • High pitch = tension, suspense
  • Low pitch = less tension, mystery
  • Loud sounds = intense, threatening
  • Quiet sounds = delicate, hesitant
  • Fast tempo = more tension
  • Silence = highlights, isolates image, can represent death, sticks out if a mistake
sound s impact on image24
Sound’s Impact on Image !
  • Sound effects both atmospheric and diagetic
  • Off screen sounds can expand the film world beyond the frame
  • Sounds can be used like motiffs and serve symbolic functions
  • Sounds can be used as to aid transitions and foreshadow action
sound s impact on image25
Sound’s Impact on Image !
  • Music

- sets a mood

- suggest historical references, a time period

- can suggest locales, classes or ethnic groups

- used as foreshadowing and musical warnings

- atonal music can create anxiety

- can reference other settings of music

- music can provide ironic contrasts with image

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