Bit Mapped Graphics and Sound

Pixel- An individual element of a picture

Resolution- Width * Height

Colour Depth- Number of bits allocated to represent the colour of a pixel in a bit mapped picture

Storage- Resolution * Colour Depth

2 ^ (no. of bits) = number of combinations

Metadata Contains: Resolution, Colour Depth and Date taken

• Just like an image, sound is stored in a computer as 1s and 0s
• The metadata tells the computer if the file is an image or a sound file
• Sound is often continously varying data (analogue) but the computer needs this in digital form as a series of 1s and 0s

• Sampling is the process of converting analogue sound waves into digital form to create what is commonly known as digitised or digital sound
• This is the analogue to digital conversion (ADC)
• An analogue sound wave is infinity variable so in order to store this digitally, a series of readings at fixed intervals are taken from the wave in order to create the discrete data values that are a defining feature pf binary data
• These readings are then stored as binary code

To calculate how large the file size will become you can use the following calculation:

Sample Rate * Length of Recording (Secs) * Sampling Resolution

e.g.

44.000 * 60 * 16 = 42,240,000 bits = 5,280,000 bits = 5.28 MB

• When deciding on the optimum sampling rate, we can refer to Nyquist's Theorem.
• "To faithfully recreate the analogue signal, you should sample at least twice the highest frequency"- [present in the original signal]
• This allows for at least two samples to take place within a complete cycle of the highest frequency wave so that you can pick up the peaks and troughs
• Samples can be edited to remove ant background noises or interferences.

• Sound synthesis is another term that is used to refer to sound which is produced digitally rather than in an analogue form
• It is synthesised or manufactured
• By definition, all sounds created by a computer are digital

• After sound has been digitally recorded, in order to hear it, we need speakers or headphones.
• In order to convert it so it can be amplified and played, we need to use a digital to analogue converter (DAC).
• Typically the DAC is embedded in the device that plays the audio data and the signal is passed in analogue form to the speakers/headphones.