Sound Flashcards
What does sound contain?
A large number of waves each with a defined frequency
How can we store sound?
We have to convert it from analogue into digital form (binary) where a sound encoder is used.
A sound encoder is made up of two parts:
-Band limiting filter
-Analogue to digital converter (ADC) - input
or a DAC - digital to analogue converter - output
How does ADC work?
An analogue sound wave is picked up by a microphone
and sent to an ADC in the form of analogue electrical
signals. Once the sound wave is converted into a digital form it can be stored and manipulated.
The amplitude of the wave has to be sampled at regular intervals.
We need to look at the number of bits to be used to store the amplitude values (sampling resolution).
We need to look at the sampling rate which is the number of samples taken per second - it should be sampled at least twice the highest frequency in the sample.
How is sound represented in analogue form?
represented by wave
forms; the height of these waves can be sampled
regularly with the height being represented by a bit-code
What is meant by sample rate?
number of samples taken per second
What is meant by sampling resolution?
no. of bits assigned to each sample
The sampling resolution allows you to set the range of volumes storable for each sample.
What can influence the quality of sound produced using a sound sampler?
sampling rate and sampling resolution
What will happen if too few bits are used in recording sound?
Significant quantisation error
What will happen if we increase sampling rate or sample resolution?
Increased file size and accuracy
What is meant by bit rate?
number of bits required to store 1sec of sound
How do you calculate bit rate?
Bit Rate = Sampling Rate×Sampling Resolution
How do you calculate sound file size?
File Size = Bit Rate×Length of Sound
How can sound be manipulated?
Once in a digital format it can have new sounds added to it, effects added such as fade in and fade out, and editing the sound to remove noise
