Audio hardware and audio software

Audio on a computer needs hardware to capture, convert and play sound, and software to record, edit, compress and play it.

Audio hardware

• Microphone: converts sound pressure into an analogue electrical signal.
• Sound card (audio interface): the main component. It contains an ADC (analogue to digital converter) for recording, a DAC for playback, a DSP for processing, a MIDI synthesiser and a mixer. It has line-in, mic-in, line-out, speaker and MIDI/game ports.
• Amplifier and speakers/headphones: the DAC output is amplified and converted back to sound waves.
• MIDI devices: keyboard, synthesiser, sequencer connected through the MIDI interface.
• Storage: hard disk, CD/DVD and flash to keep the large audio files.

 Mic -> ADC -> Computer (DSP/CPU) -> DAC -> Amp -> Speaker

Audio software

• Device drivers and operating-system audio services (Windows WDM/DirectSound, ALSA, Core Audio) that let programs use the sound card.
• Recording and editing software such as Audacity and Sound Forge: record, cut, copy, mix, add effects (echo, reverb), remove noise, change pitch and tempo.
• MIDI sequencers such as Cubase to compose and arrange music.
• Codecs and converters: compress and convert between WAV, MP3, AAC, OGG.
• Players: Windows Media Player, VLC to play audio.
• Speech software: speech recognition and text-to-speech programs.

The software controls the hardware through drivers, and the hardware does the real-time conversion between analogue and digital forms.