Audio hardware is responsible for generating, receiving, and processing audio signals, which can be either analog or digital. In this context, we limit the definition of analog signals to voltage levels.
Analog Voltage Levels
Line levels: line-in/line out operates at 0.316 Vrms level.
Microphone level: analog microphone signal operates between 1mV to 10 mV
Line In/Out: Connects to devices like CD players and mixers; typically found on PCs.
Headphone Line Out: Connects to headphone or earphone jacks.
Mic In: Used for recording, voice recognition, etc.
Headphone Jack with Built-In Mic: Supports both headphone line-out and microphone in.
Commonly, a 3.5 mm stereo audio jack is used for line-in/out.
Audio Playback Device
Built-in Speaker Amplifier
Converts line-out signals to drive a speaker.
High efficient digital Class-D amplifiers are commonly used in consumer electronics.
Speakers (also known as driver or transducer)
Mono/Stereo/Multi-Channel speaker systems
Low frequency band
Subwoofer [<200 Hz]
Mid range frequency band
Woofer [20 to 2kHz]
High frequency band
Tweeter [2kHz to 20kHz]
Full Range band
Full range speaker [~ 60/100 Hz to 18 kHz]
This commonly found in consumer electronics such as phone, TV, smart speakers, etc.
Audio Capture Devices
For practical design example see this article: https://www.hwe.design/system-design/audio-system/audio-capture
An electroacoustic transducer converting acoustic signals to electrical ones.
Amplifies the low-output voltage from analog microphones to line level before digitization.
In consumer electronics, mic in is connected to the Mic-in of the CODEC chip which has internal amplifier.
Audio Processing Device
For practical design excample please this article: https://www.hwe.design/system-design/audio-system/audio-playback
Digital Signal Processor (DSP)
Main Functions of Audio Processing on DSP
A CODEC is an audio device designed to perform two main functions: encoding analog audio signals from line-in or microphone inputs to digital form, and decoding digital audio back to analog form for line-out. It interfaces with the main processor through both control and data channels.
Consumer Electronics: These devices often feature headphone line-out jacks and built-in microphones. The CODEC and digital amplifier are generally embedded in the system for built-in speakers. For an illustrative example, refer to Audio System block diagram
Digital MEMS Microphones: Most built-in microphones in consumer electronics are digital MEMS mics that output audio in a standard digital format, typically Pulse Density Modulation (PDM).
Class-D Amplifiers: These are commonly used to drive built-in speakers due to their low cost and high efficiency.
Personal Computers: PCs usually have dedicated line-in/out and microphone-in ports. These are processed by a sound card, which primarily contains a DSP, CODEC, and various audio ports. For an illustrative example, refer to Soundcard block diagram for an example.
What are the main components in audio hardware?
The primary components include Transducers, ADC (Analog-to-Digital Converters), DAC (Digital-to-Analog Converters), CODEC, and DSP (Digital Signal Processors).