Analogue vs Digital Flashcards
(24 cards)
How does analogue recording represent a waveform?
Grooves in records or variation in magnetisation on tape.
How does digital recording represent a waveform?
Samples amplitude at regular intervals, storing binary values for each measurement.
What is an ADC and how does it work?
Analogue-to-digital converter.
Samples analogue waveform to create series of binary numbers.
What is a DAC and how does it work?
Digital-to-analogue converter.
Converts digital sound into an analogue format.
Why do people prefer analogue formats to digital?
Warm / vintage sound.
Like having physical rather than digital file.
What is the sample rate of a file?
Number of times a waveform is read per second (Hz).
What is Nyquist’s theorem?
Sample rate must be double the highest frequency captured.
What is aliasing?
Sampled at too low of a rate, creates a distorted representation of the original sound.
What happens when the sample rate of a recording is too low?
Aliasing.
What is an anti-aliasing filter?
Type of LPF set at the highest desired audible frequency.
What is jitter?
If samples are taken at irregular intervals.
How do you work out the number of possible amplitude measurements?
2 to the power of the bit-depth.
What is bit-depth?
Amount of possible amplitudes that can be taken by a sample.
How much dynamic range is given per bit in the bit-depth?
6dB
What is quantisation error?
Bit-depth is low so signal is rounded to incorrect amplitude measurement.
What is bit rate?
Number of bits transferred per second when streaming digital audio.
What is the difference between lossless and lossy compression?
Lossless - preserves all audio data.
Lossy - removes some data which is deemed less critical to perception (slight reduction in quality).
Name 4 compressed lossy formats.
- WMA
- AAC
- OGG
- MP3
Name 2 uncompressed lossless formats
- AIFF
- WAV
Name 2 compressed lossless formats.
- FLAC
- ALAC
What is the equation for bit rate?
Sample rate x Bit depth x No. channels
What are the two speeds of vinyl records?
33 rpm (longer play time)
45 rpm (better quality)
What is the speed of shellac records?
78 rpm
What does dithering mean and what is it used for?
Lowering bit-depth causes small amount of random noise on signal.
Can be used to mask quantisation error.
