Understanding Sound and Digital Audio Technologies
Sound is a vibrational phenomenon transmitted in the form of waves propagating in a determined elastic medium (commonly the air or the water). When the vibrations are produced arbitrarily, without any rhythmic sequencing, we are talking about noise.
Digital sound is the digital codification of an electric signal that represents a sound wave. It consists of a sequence of binary numbers and is derived from the digital sampling and quantification of the analogue signal that subsequently can be codified or compressed, giving rise to more compact formats (audio compression).
Key Concepts in Digital Sound
- Sampling: Consists of measuring the value of an analogue signal at a specific point in time at regular predetermined intervals.
- Quantification: For each sample, it is assigned a value that will represent the amplitude of that sample.
- Sample rate: The number of times per second that a sample is taken from a sound of the analogue signal to digitalize it. It gives an idea of the quality of the digital sound. A CD-Audio quality sound has a sample rate of 44100 Hz (44100 samples per second).
- Channels: The number of points from which the sound is emitted. A mono sound has a single channel, a stereo sound has two channels, and a 5.1 sound has five channels.
- Sample size (resolution): Indicates the amount of information bits that occupy the sample. A standard CD-Audio quality has 16 bits.
- Tone: Wave magnitude that tells us the number of complete vibrations (frequency) that take place during 1 second. The measurement unit is the Hertz (Hz).
- Intensity: Depends on the magnitude of the vibrations (wave amplitude) of the body that produces them. A sound becomes stronger the greater its amplitude.
- Pitch: Quality of the sound that allows us to distinguish between two sounds of the same intensity and tone.
Website Navigation Structures
- Linear structure: The navigation works as a book in which the pages are turned forwards or backwards. This type of pages is recommended for manuals.
- Hierarchical structure: The navigation works by means of category levels of the contents. From each individual page, it will be possible to access the upper level and the home page.
- Mixed structure: Combines hierarchical navigation with zones of linear navigation. It is the most commonly used.
- Frame structure: Consists of having a side or upper frame always visible with the access menu to the different main sections of the website. Within the same structure, hierarchical or linear relationships can be established, but the main menu of the frame must always be present.
- Web structure: All the pages provide access to the rest of the contents. The navigation can be quite confusing but offers full freedom of choice to the user.
Streaming and Multimedia
- Streaming: The possibility of playing multimedia content directly from a web server without the need to download the files to our computer.
- Traditionally, when you wanted to listen to a song or display a video that was hosted on the Internet, it had to be previously downloaded to our local computer in order to be played.
- With the new streaming techniques, whose use has proliferated on the web, this is no longer necessary. Thanks to the existing bandwidths, a continuous data flow can be assured that allows playing a video or listening to music in real time.
- Currently, most radio stations and many television stations broadcast their contents through the Internet.
- To incorporate multimedia files into a web page, different technologies based on players that support streaming are used, such as Real Player, QuickTime, Windows Media Player, or Flash Player.
Content Management Systems (CMS)
- CMS: Applications installed on the server that enable the creation of dynamic web pages and allow us to design the site independently of the content. This way, changes made in the design do not affect the contents, and vice versa.
- The CMS can be modified through the Internet, so any administrator can do it from a remote computer.
- When administering a CMS, we define an aspect in accordance with some PHP templates created by us or facilitated by user communities. These templates work as an empty presentation box into which we create the web page by adding articles, news, downloadable files, etc.
- Most CMS are freely distributable and do not require extensive programming knowledge. Another advantage of CMS is their large user communities that, selflessly, develop new modules or components that extend the possibilities of these applications. The dynamism of these pages lies in the possibility that any user can update them by adding news, downloadable files, content articles, conversations in forums, etc.
- For the creation of a web page, we will use a previously mentioned free web editor. This is the editor Kompozer, which does not require installation; we just have to double-click on its executable file to start working in the program.
- Kompozer allows the creation of Cascading Style Sheets (CSS). The CSS are standard configuration files that store information about the attributes of the different types of text that compose a web page. In this way, the content (found in the HTML document) and the format (specified in the CSS file) are separated.
- The third practice will consist of creating a full website of original theme with at least four pages containing multimedia and other elements such as lists, tables, links, etc., following a web structure. As help, the attached file “Práctica 3 – Kompozer” explains step by step how to create websites including the main “index.html” file, tables, layers, links, CSS, insertion of videos and images, etc.
Chat Applications
- Chat: Refers to the Internet service that allows us to keep written conversations instantly with other users of the Net.
- The chat includes all services able to communicate with two or more users in real time. Within the term chat service, we may encompass real-time conversations offered through instant messaging, the use of client chat programs like ChatZilla, or the use of Webchat (windows in a web page in which to read or write messages).
- Prominent amongst specific chat applications are X-Chat, ChatZilla, or mIRC, which use the Internet protocol IRC (Internet Relay Chat). To connect with a chat that uses this IRC protocol, we must have the proper client software installed on our computer (i.e., plugins).
- When accessing an IRC chat, we must register to use a username or nickname. Some chats include webcam utility and allow conversation while video is displayed; these are called video chats.
- The chat is a complementary tool in many other applications. The Web Conference or Webinar is a new communication service focused on teaching, in which a moderator gives a multimedia lecture and creates interactivity with the rest of the participants through voice, video, shared desktop, shared applications, and, as mentioned, chat.