Headphones are transducers that produce sound as they receive audio signals and are also often connected to computers (laptops, smartphones, etc.). To fully understand headphones, we must also understand audio signal flow in terms of inputs and outputs while also understanding the definitions of input and output devices in computer systems.
Are headphones input or output devices? When headphones are connected to a computer (laptop, smartphone, etc.), they receive information outputted from the computer. This means headphones are output devices. Headphones with built-in microphones are input and output devices according to the computer.
In this article, we’ll go through full definitions of input and output devices and address the role of headphones in the framework of a computer system.
What Are Input And Output Devices?
The terms input device and output device are computer-related.
An input device is defined as a device that inputs information into a computer for processing. In contrast, an output device is defined as receiving and reproducing information from a computer.
Headphones receive information from computers (think smartphones, laptops, tablets, etc.) and are, therefore, output devices.
Note that headphone transducers, by the very nature of their designs, are analog devices. Therefore, a digital-to-analog converter must be put inline between the computer and the headphones for the headphones to actually reproduce the outputted computer data.
The Input And Output Of Headphones As Transducers
As previously mentioned, headphones are transducers of energy. More specifically, they convert analog audio signals (electrical energy) into sound waves (mechanical wave energy). In this way, headphones “input” audio signals and “output” sound.
So relative to the computer, headphones are output devices, which is the truest answer to the question “are headphones input or output devices?”
However, if we take the headphones themselves as our reference point, we see that headphones input and output energy.
Headphones use drivers to convert energy. Typically these drivers are dynamic (moving-coil) drivers that utilize electromagnetic induction to function.
The electrical audio signal (an AC voltage) runs through a conductive coil attached to a movable diaphragm and sits inside a magnetic field. As the signal flows through the coil, the magnetic field causes it to move due to electromagnetic induction. This causes the diaphragm to move, which causes coinciding sound waves to be emitted from the headphones.
In stereo headphones, there are two separate signals. A left channel signal is sent to the left headphone driver, while a right channel signal is sent to the right headphone driver.
To learn more about headphones as transducers, check out my article How Do Speakers & Headphones Work As Transducers?
Reverse Order: Headphones As Microphones
Moving-coil headphone drivers are essentially wired the same way as loudspeakers but smaller in design. Dynamic headphone and speaker drivers are also wired the same as moving-coil dynamic microphones; only the signal flows in reverse.
As we've mentioned, headphones receive audio signals, which they then transduce into sound via a moving diaphragm.
Microphones, on the other hand, have movable diaphragms that react to sound waves. These diaphragms have an attached conductive coil that moves along with the diaphragm within a magnetic field.
The movement of the dynamic microphone diaphragm causes the coil to experience a changing magnetic field, and an electrical AC signal is induced across it. This signal is effectively the microphone's signal.
Microphones, according to computers and input devices. However, like headphones, if we take the mic as our reference point, we see that it has both an input (acoustic waves) and an output (electrical signals).
So it would stand to reason that a microphone could be set up and wired in reverse to act as a speaker or headphone. In the same way, a headphone could be set up and wired in reverse to become a microphone.
Of course, these devices are not designed to function in reverse, so they'd be very ineffective. However, the way they are designed would allow them to be used in reverse.
For more information on the close relationship between microphones and speakers, check out the following My New Microphone articles:
• How To Turn A Loudspeaker Into A Microphone In 2 Easy Steps
• Do Microphones Need Loudspeakers Or Headphones To Work?
• How To Plug A Microphone Into A Speaker
Headphones are transducers that require analog audio to drive their elements and produce sound waves. Computers, conversely, are digital devices that utilize digital audio rather than analog audio.
Therefore, if we are to use headphones as an output device properly, we must first convert the computer's digital audio to analog audio. This is done with a digital-to-analog converter or DAC.
Luckily, our computer devices have built-in sound cards that act as DACs. This is why we can plug our headphones into the headphone jacks of our smartphones, laptops, tablets, etc. and listen to the audio the computer is playing.
Let's say that our smartphone doesn't have a headphone jack (this trend started with Apple's iPhone 7 in 2016), and we connect our Lightning Earpods (link to check the price on Amazon) via the Lightning connector. The Lightning connector is a digital connection, while the headphones are analog. Therefore, there is a DAC immediately after the Lightning connector in the Earpod.
The same goes for Lightning or USB to 3.5mm (or other analog connection) adapters. There needs to be a digital-to-analog converter to have the adapter work properly.
However, other DACs may yield better results than built-in sound cards and consumer-grade headphones. These DACs come in professional audio interfaces.
An audio interface is really any device that allows a computer to connect to audio devices. These audio devices can be either input or output devices and include inherently analog devices such as headphones, monitors, microphones and instruments.
These audio interface I/Os generally have better sound quality and greater versatility than a computer's built-in sound card.
A common low-end “prosumer” audio interface is the Focusrite Scarlett 2i2 (link to check the price on Amazon):
Focusrite is featured in the following My New Microphone articles:
• Top 11 Best Microphone Preamplifier Brands In The World
• Top 11 Best Audio Interface Brands In The World
• Top 11 Best DAW Control Surface Brands In The World
As we see in the above-pictured 2i2, there is a 1/4″ (6.35mm) headphone output jack to the bottom-right of the device.
There are plenty of better professional audio interfaces on the market that feature multiple headphone outputs and the ability to provide various headphone mixes.
To learn more about audio interfaces, check out my article What Are Audio Interfaces & Why Would A Microphone Need One?
Some headphone amps connect directly to computers and act as digital-to-analog converters as well. Furthermore, there are dedicated DACs on the audiophile and consumer markets.
For more on headphone amplifiers and DACs, check out the following My New Microphone articles:
• What Is A Headphone Amplifier & Are Headphone Amps Worth It?
• Top 11 Best Headphone Amplifier Brands In The World
• Top 11 Best Desktop DAC (Digital-Analog Converter) Brands
• Top 9 Best Portable DAC (Digital-Analog Converter) Brands
Is a microphone an input or an output device? Microphones are input devices because they input information into a computer. Note that the mic signal must be converted into digital data before it can be sent to and used by a computer.
To learn more about microphones and their role with computers, check out my articles Are Microphones Input Or Output Devices? and How To Connect A Microphone To A Computer (A Detailed Guide).
What are the parts of a headphone? Headphones are made of several parts. The key component is the transducer element or driver, which may work on either electromagnetic or electrostatic principles. Depending on the type of headphone, there could be earcups or buds, various cables, a headband, microphone, noise-cancelling circuity, and more.
Choosing the right headphones or earphones for your applications and budget can be a challenging task. For this reason, I've created My New Microphone's Comprehensive Headphones/Earphones Buyer's Guide. Check it out for help in determining your next headphones/earphones purchase.