Audio signals represent sound as an oscillating waveform, usually as analogue or digital signals. The human audible range is between 20 Hz and 20 kHz.
What are some implications of this when outputting sound from a computer? When input, the sequence of numbers comes in rapidly, and a processor might miss some (resulting in degraded sound). For input and output, the processor uses a buffer (in the form of a queue) to store the numbers in memory.
Audio is input via this process:
- A microphone converts sound waves (pressure) into an electrical signal.
- This signal is amplified, which scales up the voltage for easier processing.
- The time-varying signal enters an analogue-to-digital converter, where it is sampled at a given frequency and output as a sequence of -bit samples.
- On the DE1-SoC, this is 24-bits wide.
And audio is output via this process:
- An input sequence enters a digital-to-analogue converter, which outputs a time-varying voltage signal.
- This voltage signal enters an amplifier to scale up the signal.
- This enters an audio output device (speakers, headphones) to convert voltage into sound waves.