2.5 Sound Flashcards
Analogue signals
Continous
Digital signals
Discrete
How is sound digitised?
By repeatedly measuring and recording the sound wave
How can a computer store sound?
It must convert it into a digital form in order to be stored and processed
ADC
Analogue to Digital Converter is used to convert inputs to digital signals
DAC
Digital to Audio Converter is used to convert digital to outputs
What is a sound sample?
A measurement of amplitude of a sound wave at a given time
How is sound sampled?
Using a bit depth and sample rate
Bit depth
Determines how closely the wave is sampled on the y-axis
Sample rate
The number of samples taken per second (measured in Hz)
Sample resolution
The number of bits (audio bit depth) used to record each measurement
What is the effect of more bits per sample?
The accuracy of the recording is increased but so does the size
1Hz = ?
1 sample per second
What is the sample rate for a typical CD?
Sampled at 44,100Hz
How to calculate sound file sizes?
File size (bits) = sample rate x bit depth x duration
What does recording quality improve?
- The more frequently we sample the sound
- The more accurately we record the wave height
What does increasing the sampling rate mean?
Recording more data points
What does increasing the bit rate increase?
The accuracy of each data point
What is the human hearing range?
20-20000Hz
Lossy compression - MP3
Removes the sound that we can’t hear easily hear or that least affect the perceived playback quality
How can lossy compression affect Sound quality?
It can reduce the sound quality which is negative
What are the benefits of lossy compression?
Useful for storing, downloading or streaming
Lossless compression
Reduce the file size when compressed but do not lose any information
Give some lossless compression formats
- FLAC (Free Lossless Audio Codec)
- ALAC (Apple Lossless Audio Codec)
- WMA (Windows Media Audio)
Give some uncompressed audio file formats
WAV and AIFF
