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Sound and hearing
The University of Colorado site Audio Processing says all there is know about the subject in a two minute capsule.
Loudness ("prothetic" attribute reference):
SPL (Sound Power Levels) dB Sound Power LevelsThe Fletcher-Munson equal loudness curve:
To quote from Music and the Human Ear:
"SPL is an objective measurement of sound pressure, or power in watts, and is independent of frequency. In 1933 Fletcher and Munson of Bell Labs did a study that showed that subjective sound levels varied significantly from the SPL level. That is, when two tones were played at the
exactly the same SPL level, one sounded louder than the other. And the results were very dependent on how loud the tones were to begin with. This is illustrated by the set of Fletcher-Munson curves. The vertical axis is the objective SPL sound level. Each of the curves in the graph represents a constant subjective sound level, which are in units called "phones." The lowest curve is the minimum audible level of sound. As noted above, the ear is most sensitive around 2-5 kHz. To be audible at this minimum level, a sound at 20Hz must be 80 dB (100 million times!) more powerful than a sound at 3 kHz.
"Near the top, the curve at 100 phones is a fairly loud level. To sound equally loud at this level the sound at 20 Hz must be about 40 dB more powerful. This change in subjective level for different loudness levels means that music played softly will seem to be lacking in bass. For years pre-amps have come equipped with "loudness" controls to compensate for this. …"
Pitch ("metathetic" attribute reference):
See theories of Pitch Perception from the authoritative notes from the course on Sensation and Perception: Hearing at the University of Sussex.
See also our dicussion of Critical Bands and Psychacoustics: Critical Bands etc.
Light and seeing
The distinction between light and seeing has taken a long time to gel. See Light and Seeing: Evolution of the Concept
Brightness ("prothetic" attribute):
Brightness, Luminance, and Confusion: a March 1993 article by Charles P. Halsted in Information Displaywhich introduces and defines the "Six Light Words."
- Light
- Luminous Flux
- Luminous Intensity
- Luminance
- Brightness
- Illuminance
The following two quotes may extend the confusion:
Visual Acuity:- "The concept that is now known as 'luminance' was for many years designated by the term 'brightness.' This led to much confusion between the objective concept of 'brightness' as intensity per unit of projected area, and the subjective concept of 'brightness' which referred to a sensation in the consciousness of a human observer. The newer term). 'luminance' was adopted to avoid this confusion. - from Optics by Francis Weston Sears (Addison-Wesley, 1949)
- "Brightness (a term of photometry): The subjective description of luminance. A perceived characteristics of objects which does not vary directly in a simple mathematical relationship with their physical or measured brightness, which is corretly termed their luminance. Brightness is often misused to mean luminance. If so, it should be qualified as 'measured' brightness, to distinguish between the absolute attributes ('measured' brightness) and the perceived attributes ('apparent' or 'subjective' brightness) of the object in question."
Luminance, Illuminance, Lumens, Lux, . . .
In case you even need to use it, here is Luminance: Unit Conversion
See Visual Acuity from Webvision: The Organization of the Retina and Visual System: from the University of Utah
Color ("metathetic" attribute):Color Science: a collection of pictures and links relating to color perception -- from the Department of Physics and Astronomy, Austin State University. See in particular the material on incandescence or "backbody" radiation -- for example.The photopic luminosity function:
The "brightness" characteristics of visual perception.
Ancient telegraphic ( distant writing ) systems
In 1883 Paul Nipkow (1860-1940) envisaged and demonstrated a complete scanning system.
Broadcast Analog TV: ReferencesWorldwide TV StandardsSpatial harmonics: Picture representation in terms of spatial harmonics is a fundamentally different communication concept which is the basis of many image compression schemes.Details of NTSC
Black and white signals:Horizontal/Vertical scan
Frame Form
Luminance signal
Spectrum
Black and White Transmitter
Black and White ReceiverComposite color signals:Discussion of NTSC color system
Examples of the nonlocalized spatial harmonic view point
Examples of a localized spatial harmonic view pointGabor Function References:
Gabor Functions
Using Gabor functions to make atmosphere in computer graphics
Gabor Model
2-D Gabor Function - Interactive Visualizationl
A wonderful set of web resources on "light and seeing; sound and hearing" collected and created by George Mather and linked to the Perception Home Page. See in particular:The Joy of Visual Perception: a web book on perception by Peter K. Kaiser of the Department of Psychology, York University.
Visual Physiology: an interactive tutorial by George Mather of the School of Biological Sciences, University of Sussex.
Lance Hahn's Retina Reference
Psychology 280 Class Notes from the University of Toronto
A Computer Model of the Auditory Periphery
The Revolution in Television Technology: a exposition of new television technologies -- from the Department of Physics and Astronomy, University of Delaware.
A Guide to Digital Terrrestrial Television Broadcasting (DTTB): an extensive report of a International Telecommunications Union (ITU) study group.
Basic Video: a useful basic reference by Roger Inman & Greg Smith from the 1996 Television Production Handbook
