RTV 332 Audio

Analog vs. digital recording Analog ‘analogous to the original waveform’ Amplitude / frequencies / magnetic recording Audio tape / video tape (amount of information) Writing speed (analog tape / video helical scan) Digital Representation of the waveform with 1s and 0s Sampling and quantizing Compression of data ‘perfect’ copy

Basic analog process Sound waves Microphone diaphragm (transducer) Magnetic recording (encoding) Noise Generations Playback (decoding) Speakers (transducer)

Basic digital process Sound waves Algorithm for encoding (PCM) Sampling (‘snapshots’) Quantizing Sampling rate Compression (MPEG variations) (lossy?) Decoding Various codecs

Sampling rates Analog: amplitude is the level component and frequency is the time -- digital, quantizing is the level and sampling is the time component 32 kHz: original broadcast digital audio 44.1 kHz: CDs ° 48 kHz: DAT and miniDV 96 kHz or 192 kHz: BluRay

Sampling rates The Nyquist–Shannon sampling theorem: perfect reconstruction of a signal is possible when the sampling frequency is greater than twice the maximum frequency of the signal being sampled,Nyquist–Shannon sampling theorem For example, if a signal has an upper band limit of 100 Hz, a sampling frequency greater than 200 Hz will avoid aliasing and would theoretically allow perfect reconstruction.band limitaliasing

Sampling rates The full range of human hearing is between 20 Hz and 20 kHz. The minimum sampling rate that satisfies the sampling theorem for this full bandwidth is 40 kHz. The 44.1 kHz sampling rate used for Compact Disc was chosen for this and other technical reasons. Aliasing: the distortion or artifact that results when the signal reconstructed from samples is different from the original continuous signal.

Digital Recording Sampling: takes periodic samples (snapshots, voltages) of the analog signal and converts that information into digital data Sampling frequency: the rate at which the signal is sampled: 44.1 kHz, 48 kHz Think of film at 24 fps – each still frame is a ‘sample’ (snapshot) of information in 1/24 of a second

Digital Recording Quantization: how many ones and zeroes to represent each sample A quantity expressed as a binary number is called a digital word. 10 is a 2-bit word, 101 is a 3-bit, 1010 is a 4- bit etc. The greater the number of the quantizing level ( an 8 bit vs. 10, a 2 bit) the more accurate the representation of the analog signal.

Sound in an environment Sound wave Compression / rarefaction Frequency / Measured in hertz Amplitude / Measured in decibels (db-spl) AM/FM, kHz / MHz (r.f.) Attack/sustain (internal dynamics)/decay -- sound envelope Acoustics / Psychoacoustics / binaural hearing Absorbed / Reflected Direct / Indirect (echo & reverberation)

Sound Frequency Spectrum Bass Low bass, 1st & 2nd octaves, Hz Upper bass, 3rd& 4th octaves, Hz Midrange 5th, 6th & 7th octaves, ,048 Hz Upper midrange: 8th octave, 2, ,096 Hz Treble 9th & 10th octaves, 4, ,384 Hz

Mics -- Review Sound Sound Frequency Spectrum Bass, midrange, treble Frequency / Hertz Amplitude / decibels Acoustics Direct / indirect sound Echo / reverberations

Microphone Directional Patterns Omnidirectional / nondirectional Unidirectional / Directional/ cardioid Super, hyper, ultra Bidirectional

Main polar patterns Omni / nondirectional Bi-directional / figure 8 Unidirectional / directional / cardioid

Cardioid range Cardioid Supercardioid Hypercardioid Shotgun mic is hyperdirectional Phase cancellation

The omnidirectional microphone is equally sensitive in all directions 16

Use a supercardioid pickup pattern whenever you want extremely selective pickup, to avoid environmental noises, or for distance sources. 17

The directional (or cardioid) mic has a broad, heart-shaped pattern that is insensitive on its rear side 18

Professional Mic types Moving coil/dynamic Ribbon Capacitor/condensor Transducer – changes energy from one form to another – in this case sound waves into an electrical current

More about mics and sound Close vs. distant miking Cross-pair, mid-side as some distant miking approaches Close mic speakers on camera / filmmaking wide shots must do ADR Wide response – range of frequencies the mic will pick up Flat response – accurately recreates frequencies Colored response – changes frequencies (lavaliere boosts high frequencies, for example

Common mic types lavaliere headset handheld studio/boom mounted TV boom types / largest to smallest Perambulator boom, giraffes, fishpole PZM (boundary mic)

Audio is as important to television as the video image.  It gives images a convincing realism.  It helps the audience feel involved.  It helps you follow the story. 22

Successful audio is a blend of:  Appropriate techniques  Appropriate artistic choices  Both of these are a matter of technical knowledge combined with experience. 23

THE VARIETY OF ANGLES OF THE SET WALLS, THE CURTAINS, CARPET, FURNITURE, AND PEOPLE HELP DAMPEN THE LIVE SOUND – BUT NOT TOO MUCH 24

Acoustic panels were placed on the walls of this audio room to reduce the “liveness” of the room 25

Mono sound:  “Single-eared” monaural representation of sound in space Stereo sound:  Creates illusion of space and dimension Surround sound:  Provides sense of envelopment when mixed correctly 26

During the shooting of a dramatic program, the boom operator gets the microphone as close as possible, while still being off camera, because open-air sound does not usually travel far 27

Shotgun mics are commonly mounted on field cameras, especially for news shooting (nat) 28

 Shotgun mics give the best quality long-distance pickup from the subject  Must be aimed accurately But, when attached with the camera:  Sometimes too far away from the subject for the best sound  Mic doesn’t zoom with the zoom lens, so the sound capture remains the same --- ‘presence’ issue  Camera mic can’t follow somebody 29

The handheld mic is widely used for interviews and commentaries, and stage work. If the mic has a cardioid directional response, extraneous noise pickup is lower. If the mic is omnidirectional, it may need to be held closer to the subject to reduce atmosphere sounds 30

Different types of wind screens are used to protect a shotgun mic from wind noise 31

A Mic Boom (or fishpole) is a regular method of mounting the shotgun mic, particularly in the field. It allows the operator to stand several feet away from the subject 32

Lavalier mics come in different shapes and sizes. Generally. A lavalier mic is clipped to a necktie, lapel or shirt. Sometimes a “dual redundancy” pair is used when a standby mic is desired 33

This lavalier clip is designed to hold two microphones, providing a backup in case one fails 34

The boundary (pzm) mic is a low-profile mic that can pick up accurate sounds from six or more feet away 35

There are many types of mic stands and mounts, from bottom-weighted telescopic stands to small versions with thin, flexible, or curved tubing intended for lavalier or miniature mics 36

Wireless (radio) belt pack and transmitter. A lavalier mic or a handheld mic can be plugged into the transmitter (XLR or other connector) 37

VU meters and bar graphs are used to monitor the audio signal 38

A large surround sound audio mixer for television productions – faders, EQ, pan pots, trim, assign 39

40 …parts of the console / mixing sound, as time permits …mixing vs. layering sound …audio console vs. DAW Chapter 10 Audio for Video