Speech

Human speech has become a system of communication requiring coordination of voice, articulation and language skills. Voice is produced by the movement of air which vibrates through the vocal cords.

Vocal chords are made of elastic connective tissue covered by folds of membrane. The pitch of your voice is controlled by the modification of the muscles that shorten the cords pulling them tight for high pitch and slack for low pitch.

Articulation is the modification of airflow. Speech is articulated by the movements of the tongue, lips, lower jaw and soft palate. Vowels come from voiced excitation of the voice tract. Articulators are kept static and all sound radiates from the mouth. Nasals are generated when the tongue is raised and the soft palate is lowered which reduces the oral passage. Plosives are generated when the vocal tract is closed by the thr tongue or lips and then the pressure built up is suddenly released. Fricatives are formed by partially restricting the vocal tract by the tongue or lips.

The Moving Image and Video

The first moving image was introduced to the television in 1926 by John Logie Baird. This was based on the old idea of Persistence of Vision (PoV). PoV is the theory that the eye has a retention of an image of about 1/25th of a second and therefore if a secondary image was viewed before this persistence ends then the observer would not notice the change of images.

The image shows an early toy called the Zeotrope which created the illusion of motion. This was invented in 180AD and then a modern version was reinvented in 1833. The viewer looked through the slits and because of the speed at which the images were rotating it created the illusion of motion despite it actually being a series of still images.


This theory is now regarded as the myth of persistence of vision. The more plausible theory now is that there are two distinct perceptual illusions in phi phenomenon and beta movement.

Bitrate is the word used to describe how many bits are required to show a video per second. This can vary from as low as 300kbps sor a low quality video, upto 8000kbps for a high quality video.
Interlacing is a way of getting the best results from a low bandwidth. It is done by alternating showing the odd numbered lines on the television first, then the even numbered lines of the next image at a speed of 25 frames per second. This gives the illusion that the images are moving.
Resolution is the number of pixels a televison can display. When analogue TV was used, typical resolution was 352x288 in Europe. Comparitively, modern televisions can display as many as 1920x1200. DVD quality is typically 720x576 for European televisions, while Blu-Ray and HD provide the highest resolution.

File Format

MPEG-1 - First designed in 1988 was the first decoder and could compress a video to about 26:1 and audio 6:1. Designed to compress vhs quality raw data with minimum loss in quality.

MPEG-2 - The improvement to MPEG-1 and is the format of choice for digital television broadcasters. It actually developed as early as 1990 before MPEG-1 was released.

MPEG-4 - Integrates many features of previous versions while adding support for 3-D rendering, Digital Rights management and other interactivity.

Quick Time - Appeared in 1991 created by Apple almost a year before Microsofts equivalent software.
It can handle playback from VLC and MPlayer both which are PCLinuxOS based.

AVI - Appeared in 1992 by Microsoft. A problem with this format was that it could appear stretched or squeezed during playback however the players such as VLC and MPlayer solved most of these problems. But a massive advantage of it is that it can be played back on almost every player and machine making it second only to MPEG-1.

WMV - Made by microsoft using several codecs and is used for BluRay discs.

3GP - Used for CDMA phones in the US. Some phones us MP4.

FLV - Used to deliver video over the internet and is used by YouTube, Google Video, Yahoo Video, Metacafe and other news outlets.

Intro to Cool Edit Pro

CoolEditPro is a piece of software which allows you to view a sound file in its digital format and then allows you to edit this wave. You can choose from which point you want to listen to the sound file or even select a specific section to play by highlighting the section.

The wave can be manipulated in various different ways such as copying, pasting and trimming the whole wave or selected parts of it. Additionally you can add other waves onto or into the file to extend it. When the wave is open it is possible to change the data about the wave being displayed on the screen such as the time, time signature or changing the scales to allow more accuracy.

It is also possible for the user to zoom in and out of the wave to allow greater detail and closer selections. Other affects available to the user are things such as reverse and invert which change the pattern of the wave and therefore how the wave sounds. The amplitude can be changed which changes the volume of the sound file and can also be faded to allow quieter sections or merges of two sounds. Other features are things such as delay, reverb, echo etc.

Looking at Light

The concepts of looking, seeing and observing are very different. The definitions of looking is readying yourself to see something, seeing is when the eye actually receives light energy and converts it into impulses and observing is when we analyse, interpret and decide what the nerve impulses are i.e. object or an effect.

On cloudy days light appears white however it has a bluish tint. The clouds actually act in such a way that they soften the light and diffuse it, spreading it out.

Front lighting occurs when the light source is behind the person observing the object which evenly lights the object. Side lighting creates strong shadows which emphasizes texture and adds depth to an image. The most dramatic lighting though is back lighting meaning the light source is behind the object creating silhouettes and other interesting effects.

Light

Light is defined as a form of energy detected by the human eye and has been observed to be able to travel as both streams of particles and in waves. Light is different from sound, sound needs a medium to pass through in outer space in order to travel, where as light can travel directly from the sun through the vacuum of space  in order to reach earth.

Light travels as a transverse wave much like a ripple on the surface of the water. It travels at right angles both up/down and right/left from the point of origin. Light works the same as radio waves, each colour is a different frequency and the eye acts like a radio receiver. The frequency range is 400THz (RED) to 750THz (VIOLET).

Light Travels at 300000000 m/s in a vacuum, it slows down a little in air and slows to 2/3rds in glass. The slowing off light in glass makes that material useful for lenses. The frequency is the vibrations per second and the frequency of the lightwave is independent of the medium which its travelling in. The same lightwave would have a different wavelength because the speed of light is slower in glass.

White light is made up of every colour of the spectrum though some colours are more prominent than others.

Above is shown the light spectrum of visible light and then both extremes of wavelength which the eye cannot detect. Each light source has a different reaction to each frequency of different colours. Waves which have wavelengths of longer than 700 nm are infrared and those with wavelengths shorter than 400nm are ultraviolet. 50% of sun energy is visible to us on the earths surface and about 3% is ultraviolet leaving the rest being infrared.

Monochromatic light (single colour) is uncommon however is used in street lighting. Under this type of lighting the world appears to be in shades of grey and completely colourless.

Brightness is measured in candela and lumen by scientists but photographers use light exposure meters that have been set up by scientists. A candela is the power emitted from the source in a particular direction. The  units of candela emitted from a standard candle is 1 candela. A lumen is the total amount emitted from a source irrespective of the the ability of the eye to see it.

Light waves once emitted from the source are transmitted, reflected, absorbed, scattered and refracted. Transmitted light is the same as emitted light, it simply describes the act of the source producing light waves. Reflected light is when light bounces off of a solid object i.e. a mirror. The angle of reflection is the same as the angle the light hits the surface (angle of incidence).

The reflection shown in the diagram is know as SPECULAR reflection however there is also DIFFUSE reflection which happen when the light waves contact a rough surface. The light can reflect in many directions which is known as Scattered light. Absorbed light is light waves that come into contact with a solid surface but do not reflect. Instead they are absorbed and disappear. Refraction takes place when light waves pass into a transparent object and then when they pass back out the other side. It is basically the act of the light bending. When the light waves pass into and out of the medium they speed up or slow down depending on
the speed of light in that particular medium. This explains why it is difficult to see things that are submerged in water and why they appear bent, because the light is bending as it passes from travelling through water to travelling through air to reach the observers eye.

The Inverse Square Law states that the intensity of the light at a point is directly proportionate to the square of the distance from the light source.