Odisha CHSE +2 Vocational Audio Video Technique flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Wavelength formula for sound

Wavelength equals the speed of sound divided by frequency (λ = v/f). At 343 m/s, 100 Hz gives about 3.43 m and 1 kHz about 34 cm.

Decibel sound pressure formula

Sound pressure level in decibels is 20 log10(p/p0), where p0 is 20 micropascals, the nominal threshold of hearing at 1 kHz. Doubling pressure adds about 6 dB.

Inverse square law audio

In a free field, sound intensity falls to one quarter when distance doubles, a level drop of about 6 dB per doubling of distance from a point source.

Audible frequency range

Human hearing typically spans 20 Hz to 20 kHz. Frequencies below 20 Hz are infrasound and above 20 kHz ultrasound; sensitivity is greatest between about 2 kHz and 5 kHz.

Reverberation time RT60

RT60 is the time for sound to decay 60 dB after the source stops. Sabine's formula is RT60 = 0.161 V/A in metric units, with V in cubic metres and A in sabins.

Haas precedence effect

When two copies of a sound arrive within about 50 ms, the listener perceives a single sound from the first arrival direction; the delayed copy mainly adds loudness and timbre.

Equal-loudness contours

Fletcher–Munson contours show that perceived loudness depends on frequency. At low levels, low and high frequencies sound quieter than mid frequencies for the same sound pressure level.

Nyquist sampling theorem

A signal must be sampled at more than twice its highest frequency to be reconstructed without aliasing. CD audio uses 44.1 kHz, allowing content up to about 22.05 kHz.

Bit depth dynamic range

Each additional bit adds about 6.02 dB of theoretical dynamic range. Sixteen-bit audio gives roughly 96 dB, while 24-bit gives roughly 144 dB before practical converter limits.

Phantom power

Phantom power is +48 V DC supplied through the microphone cable, usually on XLR pins 2 and 3. It powers condenser microphones; ribbon microphones may be damaged and should not receive it.

Cardioid polar pattern

A cardioid microphone is most sensitive at the front and rejects sound from the rear. Its pickup angle is about 131 degrees, making it useful for reducing stage or monitor bleed.

Condenser versus dynamic microphone

A condenser uses a charged capacitor element, is sensitive and detailed, and needs power. A dynamic uses a moving coil, handles high sound pressure, and needs no phantom power.

Gain staging in mixing

Set input trim so average levels sit near nominal, often −18 dBFS, and keep faders near unity. This preserves headroom, avoids clipping, and keeps noise low through the chain.

Progressive versus interlaced video

Progressive video captures complete frames in sequence. Interlaced video captures two fields per frame, odd then even lines, giving smoother motion but visible combing on moving edges.

180 degree shutter rule

For natural motion blur, set shutter speed to twice the frame rate, equivalent to a 180-degree shutter. At 25 fps use 1/50 s; at 50 fps use 1/100 s.

HD and UHD resolutions

HD 1080 is 1920 by 1080 pixels. UHD 4K is 3840 by 2160 pixels, exactly four times the pixel count of 1080p and normally displayed in a 16:9 aspect ratio.

Additive and subtractive colour

Displays mix additive primaries red, green and blue to make white. Print and filters use subtractive cyan, magenta and yellow, which remove wavelengths from white light.

PAL and NTSC

PAL is a 625-line, 50-field-per-second analogue colour system used in India and Europe. NTSC is 525 lines at 60 fields, used in North America and Japan.

Chroma subsampling 4:2:2

4:2:2 records full luminance resolution but half chrominance resolution horizontally. It saves bandwidth while preserving more colour detail than 4:2:0, which halves colour in both directions.

F-number and exposure

The f-number is focal length divided by aperture diameter. Each standard stop, such as f/2.8 to f/4, halves the light reaching the sensor and doubles depth of field approximately.

White balance

White balance tells the camera what colour white should be under the current light. Tungsten preset is about 3200 K, daylight about 5600 K; manual balance uses a white or grey card.

Neutral density filter

An ND filter reduces light entering the lens without changing depth of field. ND 0.3 cuts one stop, 0.6 cuts two stops, and 0.9 cuts three stops.

Three-point lighting

Key light is the main directional source, fill softens its shadows, and back light separates the subject from the background. Key-to-fill ratio controls contrast and mood.

Rule of thirds

Divide the frame into a three by three grid and place important subjects or horizon lines near the lines or intersections. It usually gives a more balanced composition than centring everything.

AV script two columns

An audio-visual script has video described in one column and corresponding audio, dialogue or music in the other. Each row represents the same moment in the programme.

Shot list

A shot list is a numbered production checklist giving shot size, angle, camera movement, location and notes. It helps the crew shoot coverage efficiently and match the script.

J-cut and L-cut

In a J-cut the audio of the next shot starts before its picture. In an L-cut the audio of the previous shot continues over the next picture. Both smooth transitions.

Loudness normalisation

Broadcast delivery often targets −23 LUFS under EBU R128 or −24 LKFS under ATSC A/85. Loudness normalisation balances perceived level rather than only peak level.

Studio signal chain

A typical chain runs microphone to preamplifier, mixer or switcher, recorder and monitor. Line level is usually +4 dBu balanced, while microphone level is much lower and needs gain.

Clapperboard sync

The clapperboard creates a visible closure and a sharp sound at the same instant. Aligning that frame and waveform in post synchronises separate picture and audio recordings.

Adaptive bitrate streaming

Adaptive streaming encodes several quality levels and switches the player between them as bandwidth changes. HLS and MPEG-DASH are common protocols; this reduces buffering on variable networks.

Viva voce

An oral examination in which the candidate explains and defends project decisions, equipment choices and technical results. Clear justification and accurate terminology matter more than memorised definitions alone.