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Digital and Analog Audio

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Reece Burrows

on 21 January 2014

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Transcript of Digital and Analog Audio

Bluetooth is a wireless signal emitted by mobile phones that can connect to other devices such as other mobile phones and computers, data can be sent between the devices, the transmitted data is divided into packets and then sent.
The initial discovery of the phonograph inspired many people to create more advanced of the phonograph such as the Gramophone and the Telegraphone. Without these advancements modern digital music would non-existant.
AUDIO
Analogue audio
The first analog playing and recording device was the phonograph which was created by Thomas Edison in 1877.
Thomas Edison designed the Phonograph in a way that when the sound was recorded by a vibrating needle onto the aluminum through the cone-shaped component, it is then reversed and a needle picks it up through vibrations in the grooves and emits a sound through a diaphragm. Which functions as a sound amplification device.
Music storage and distribution
Digital Audio Editing
Digital audio
The first step in creating digital audio is a proccess known as Audio Digital Conversion or ADC.

ADC uses pulse code modulation in order to rewrite anolouge audio as digital audio.
Digital audio editing software is an application for manipulating digital audio. most music artists in the modern day take advantage of these digital audio editing suites to add effects to there music such as filters,noise reduction, reverb, flanging, equalization and compression. its at this point that the ADC conversion (audio to digital conversion) process takes place to change the audio file formats and the sound quality.
LP Record
A good example of a rather popular type of record adopted as a new standard by the entire record industry. Used from 1948 and onwards, the LP record or vinyl record had only one new feature and that was the microgroove. The microgroove was basically a smaller groove that allowed longer tracks to be fit onto the record. Originally the LP record could only fit 22 minutes of music on, it later increased by 7 minutes and later even more by playing the record at a low signal (not as loud due to less RPM).
Pulse-code modulation was invented by
British scientist Alec Reeves in 1937 and
was used in telecommunications applications
long before its first use in commercial
broadcast and recording.
You can clearly see the grooves in the record displayed below, the needle type device wobbles through the groove and this emits different sounds.
Digital audio is useful in the recording, manipulation, mass-production, and distribution of sound. Modern online music distribution depends on digital recording and data compression. The availability of music as data files, rather than as physical objects, has significantly reduced the costs of distribution.
A digital audio signal may be encoded for correction of any errors that might occur in the storage or transmission of the signal, but this is not strictly part of the digital audio process. This technique, known as "channel coding", is essential for broadcast or recorded digital systems to maintain bit accuracy. The discrete time and level of the binary signal allows a decoder to recreate the analog signal upon replay.
Communication methods
Transmission Methods
Communication through music has few different methods although I will just touch on some of the different communication methods, one of the first things I will mention is the use of the radio.
Digital audio continued
Communication can be done over the radio, where multiple people can tune into a certain frequency and talk through a walkie talkie type device.
Analogue and Digital
Fibre optic is not really used to boost any music potential but using fibre optic has its benefits for buying and downloading music from the internet. Fibre optic is an optical method of transmission it uses light that reflects through tiny tubes instead of using electricity. Fibre Optic is currently the fastest transmission method, sharing music across the internet will be phenomenally quick.
These days a radio signal is picked up wirelessly through electromagnetic radiation, radio's still heavily depend on analogue signals to work compared to TV's which now only work with digital signals.
Transmission Media and Topologies
Serial and parallel communication
Serial communication is the process of sending information one bit at a time. An example of this is a radio.
since the transition to the digital music platform it has greatly expanded the the storage potential of the music media type.

a large advantage over the anologue generation of music is that between the ability to compress the file size of music media making it smaller the storage options for music have increased in size via blu ray disc's and thumb drives.
Parallel communication is a
method of sending multiple
bits simultanteously. an example of this
is a mobile phone.
parallel communication is faster than Serial communication although multiple lines can cause slowdowns among other problems. If both Serial and Parallel channels operated at the same clock speed and lets say the Parallel could convey bits 8 times at once then it would be x8 faster than the Serial channel.
Walkie talkies are analogue two-way transeiver devices which use a half duplex channel to communicate, this effectively means than the walkie talkies share a channel instead of having their own therefore the receiver must wait for the sender to finish their message before sending thereself.
Communication methods continued
There are a few more communication methods. Such as the simplex the simplex refers to communication that occurs in one direction only, this is where all the signals can only flow in one direction and the receivers cannot send any data back such as broadcast radio or television.
A full-duplex allows the receiver and sender to communicate in each other in both directions simultaneously unlike half-duplex which is only able to be sent once the other sending end has finished their message.
Error checking
A cyclic redundancy check (CDC) is an example of an error checking method which is designed to detect accidental changes to digital data. It takes the data input and checks that the remainder result (the 8th bit of the sequence) of the receiver is correct compared to the sender.

There are 5 main types of Topologies. The main 5 are as follows...
- Tree
- Bus
- Star
- Ring
- Mesh
This image shows a few more of the topology types such as the hybrid, mesh and tree topologies.
For example we have 7 bits of information in binary coding (1011010) it would count all the 1's and then decide the remainder by checking if the added up number was even or odd. If it is even it would be 1 if it is odd it would be 0, so it would be 1 because 4 is an even number so it would be (10110101)
Transmission Media Types
Cables
also distribution methods via the use of digital distribution have improved sales drastically via downloads through sites like I-tunes allowing for larger storage capacity devices and media that requires less storage space meaning that you can get more songs on smaller, portable devices such as i-pods and phones.
DSL or Digital subscriber line is a method of providing internet access by transmitting data over telephone lines, unusable upstream and downstream channels of the DSL is split into 2 different channels where it reduces amount of interference between used lines, the amount of data sent and how quickly depends on the quality of the telephone lines among many other things.
Coaxial: coaxial cables are comparatively cheaper than the other types and as a result they have a lesser transmission distance therfore if it is used for something relativly close range such as cables used for moniter connections.
Optical Fibre: Optical fibre cables have a higher bandwith capability and can transmit larger amounts of information faster. another advantage of fibre optic cables is that they are immune to electromagnetic interference.
Twisted pair: twisted pair cables are by far the cheapest of the three and come in shielded and unshielded types. while the unshielded variety is more suceptible to electrical interference the shielded type is much larger and more expensive than the unshielded cable.
The diagram above shows 3 of the different topology types available including the star the bus and the ring type.
the hybrid topolgies are combinations of two or more of the basic topologies in order to create a more advanced network topology.
Checksums
Encapsulation
Addresses
Recording Analog Audio
The address of a computer is the location of the computer over the internet, this is called an IP address or internet protocol address. The IP address is a numerical label assigned to each device.
An analog recording is one where a property or characteristic of a physical recording medium is made to vary in a manner analogous to the variations in air pressure of the original sound.

Generally, the air pressure variations are first converted (by a transducer such as a microphone) into an electrical analog signal in which either the instantaneous voltage or current is directly proportional to the instantaneous air pressure (or is a function of the pressure).

The variations of the electrical signal in turn are converted to variations in the recording medium by a recording machine such as a tape recorder or record cutter—the variable property of the medium is modulated by the signal.

Examples of properties that are modified are the magnetization of magnetic tape or the deviation (or displacement) of the groove of a gramophone disc from a smooth, flat spiral track.
IP addresses are actually binary code converted into numbers so that it can be deciphered by humans, Static IP addresses are manually assigned to a computer by an administrator. Compared to dynamic IP addresses, which are assigned either by the computer interface or host software itself.
Above we an example of the binary being decoded into the IP address, you can clearly see that each number is 8 bits or 1 byte, we looked at an example of binary in error checking.
A frame is a digital data transmission unit that includes frame syncronization.
It does this by making a sequence of bits or symbols making it possible for the reciever to detect the beginning and end of the the packet in the stream. If a reciever is connected inbetween it will ignore the the data until a new frame is syncronized.
A checksum is a digit representing the sum of the correct digits in a peice of stored or transmited digital data, against which later comparisons can be made to detect errors in the data.
The reason binary is coded in 8 bits is because if it was to be coded 2 bits per letter then only 4 symbols could be displayed due to the lack of variety of deciphered digits whereas 8 bits could display all 256 symbols due to the complexity of the algorithm.
Grading Criteria
A packet is a collection of data that can be used by computers which need to communicate, usually as part of a network. A packet consists of two kinds of data, control information and user data. The computer uses the control information to where, how to send the data. User data is the actual information that computer is trying to send.
Sequence numbers label the packets and help the receiving machine sort and reasemble the packets into a file for instance. a real life example of this is the motorway, like the internet people may use different routes to get to a certain destination, if 6 people travelled to London we could reassemble them in a group because of their name for instance.
A checksum is a simple error checking method which is used to correct single bit data errors.

these errors are calculated by creating binary values from packet data through the use of an algorithm.
from there the results are stored with the data.

when that data is retrieved a new checksum is made and compared to the original if the binary from new checksum doesnt match the original it shows that there is an error in the data.
Sequence numbers
It is more reccomended to use cyclic redunchecks for more complicated error checking.
Ecapsulation is the process of enclosing a set of elements into a new entity. For instance a procedure encloses a series of instuctions. likewise a complex data type encloses a set of properties. Encapsulation also can be used to produce an abstraction
and/or implement information hiding.
Transmission methods
Digital Audio
A datagram is a small packet of data which carries a source and destination for routing. A datagram also travels from a source computer to a destination computer via a packet switched network.
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