General Definitions

Question 1

Forensic audio

Answer 1

The scientific examination, analysis, comparison, and/or evaluation of audio in legal matters

Question 2

Soundwave

Answer 2

What sound is made of

Pressure - rarefaction

Question 3

Hertz

Answer 3

Frequency of waves/cycles over one second

Question 4

Amplitude

Answer 4

Measurement of the amount of energy transferred by a wave (represented visually by height of the wave)

Question 5

Sound (waves)

Answer 5

Vibrations that travel through the air or another medium and can be heard when they reach a living things ear

Question 6

Audio

Answer 6

Of, relating to, or employed in the transmission, reception, or reproduction of sound

Question 7

Nyquist theorem

Answer 7

To reconstruct a continuous analog signal from its sampled version accurately, the sampling rate must be at least twice the highest frequency in the signal

200 hz = 400 sample
2000 hz = 4000 sample
Etc

Question 8

Lossy audio formats

Answer 8

AAC, MP3, RM, OGG, DBB, AMR, WMA

Question 9

Lossless audio formats

Answer 9

ALAC, AIFF, DSD, FLAC, MQA, WAV, WMA

Question 10

Two ways of seeing digital audio

Answer 10

Waveform analysis, spectrogram analysis

Question 11

Three types of sound

Answer 11

Tone, harmonics, percussion

Question 12

Authentication

Answer 12

The process of substantiating that the data is an accurate representation of what it purports to be

Question 13

SNR

Answer 13

Signal to noise ratio - signal is what you want, noise is what you don’t want

Question 14

Echo/reverb

Answer 14

Live sound in an environment

Question 15

Lens distortion

Answer 15

Any kind of distortion created by defects in the lens

Barrel (wide angle), pincushion (telephoto), and mustache (both)

Question 16

Types of shutters

Answer 16

Global, rolling

Question 17

Frame averaging

Answer 17

Allows you to average luminence values of pixels over successive frames, allowing for removal of noise/distortion

Question 18

Interpolation

Answer 18

The process of determining an unknown value within a sequence based on other points in the set

Question 19

Extrapolation

Answer 19

The process of determining an unknown value outside of a set based on the existing curve

Question 20

Interpolation methods

Answer 20

Nearest neighbor

Bilinear

Bicubic

Question 21

Aspect ratio

Answer 21

The relationship of the width to the height of an image

Errors in AR can distort how an image looks

Question 22

Storage Aspect Ratio

Answer 22

The number of pixels wide by the number of pixels tall stored for the image/video

Question 23

Pixel Aspect Ratio

Answer 23

The relationship of the width of one pixel to its height (also known as sample aspect ratio!!!)

Question 24

Display Aspect Ratio

Answer 24

The relationship of the width of the full image to the height of the image when displayed correctly

Equivalent to SAR x PAR

Question 25

LEVA

Answer 25

Law Enforcement and Emergency Services Video Association

Question 26

Resolution

Answer 26

Basically the same as pixel count - the more pixels/the higher the resolution, the more data in the file

Question 27

Increasing size

Answer 27

Increasing size of an original does not increase detail Increasing size requires adding more pixels New pixels will be calculated from existing data and will not reveal additional details

Question 28

Nearest neighbor

Answer 28

Interpolation method where new pixels existing value comes from a nearby pixel No new color/luminence values are created if size increases in a whole number - 100%, 200%, etc

Question 29

Bilinear

Answer 29

Interpolation method where pixels are created based on the arithmetic mean between existing pixels/the difference between new pixels New pixel values created!

Question 30

Bicubic

Answer 30

Interpolation method that attempts to find a third order polynomial which approximates the curve represented by existing points No original values appear in this interpolated image