Sound
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Why can’t Analogue data be stored in its original form?
Analogue data is continuous so it can’t be stored
Why can Digital data be stored?
Digital data is discrete so can be stored as an electrical voltage which can be represented as a bit pattern
How do you convert from Analogue to Digital sound
• A microphone records the analogue signals • It converts this into an electrical voltage • This is converted into binary values by the ADC which samples the data at a given frequency, to be stored in the computer
What are the steps of converting from Digital to Analogue?
DAC’s convert digital data into a continuously varying analogue signal
How do you convert from Digital to Analogue sound
-This binary data is turned back into electrical voltage by the DAC, then a speaker moves according to the electrical voltage producing analogue sound
What is the aim of taking samples at regular intervals?
To create an approximation of the original sound wave
What is Sample rate?
Sample rate is the amount of samples taken per second
State Nyquist’s Theorem.
The sound must be sampled at a rate that’s twice the highest analogue frequency to recreate an accurate representation of the original soundwave.
What is sample resolution?
The number of bits used to store each sample
How does sample rate and resolution affect the stored data form of the audio?
The higher the sample rate and resolution, the better the sound quality and the larger the file size
State the two formulas for representing file size in mono or stereo
Mono : Frequency x Sample resolution x length Stereo : Frequency x Sample resolution x length x 2
What is MIDI and what does it stand for
Musical instrument digital interface is used to synthesis musical instruments. It’s used for editing, recording and playing back music.
What are the advantages of using MIDI
• Music can easily be manipulated or transposed • Provides access to individual musicians, doesn’t require a whole orchestra • Is straightforward to create a musical score • Better sound quality (no background noise)
How does amplitude and frequency affect the sound and what is frequency stored in?
Amplitude affects the volume, frequency affects the pitch. Frequency is stored in hertz