RTV 332 Audio

1. RTV 332Audio

2. 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

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

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

5. 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

6. 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, • 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.

7. 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.

8. 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

9. 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 (10010110 an 8 bit vs. 10, a 2 bit) the more accurate the representation of the analog signal.

10. 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)

11. Sound Frequency Spectrum • Bass • Low bass, 1st & 2nd octaves, 16-64 Hz • Upper bass, 3rd& 4th octaves, 64-256 Hz • Midrange • 5th, 6th & 7th octaves, 256 - 2,048 Hz • Upper midrange: 8th octave, 2,048 - 4,096 Hz • Treble • 9th & 10th octaves, 4,096 - 16,384 Hz

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

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

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

15. Cardioid range • Cardioid • Supercardioid • Hypercardioid • Shotgun mic is hyperdirectional • Phase cancellation

16. The omnidirectional microphone is equally sensitive in all directions

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

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

19. 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

20. 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

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

22. 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.

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

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

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

26. 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

27. 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

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

29. 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

30. 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

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

32. 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

33. 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

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

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

36. 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

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

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

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

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