Headphones, earbuds and headsets have become extremely popular with the rise of portable audio players, smartphones and gaming consoles. If you’ve ever wondered how your headphones work, this detailed article is for you.
How do headphones work? All headphones act as transducers that convert audio signals (electrical energy) into sound (mechanical wave energy) via a movable diaphragm and a driver that causes movement in the diaphragm. There are various headphone types and several driver types that allow this transduction to happen properly.
In this article, we’ll discuss how headphones work in general; how each type of headphone driver functions, and how the different headphone designs work to get you the audio you need to hear. When appropriate, I’ll include diagrams/illustrations to help improve the explanation.
Related article: How Do Microphones Work? (A Helpful Illustrated Guide)
Table Of Contents
This is going to be a long and in-depth article so a full table of contents is appropriate:
- The Headphone Transducer
- Definitions Of Sound And Audio
- What Is A Headphone Driver?
- Additional Information On Headphone Audio
- How The Different Varieties Of Headphones Work & Fit
- How Do Wireless Headphones Work?
- How Do Noise Cancelling Headphones Work?
- Related Questions
The Headphone Transducer
Understanding how headphones work starts with understanding how transducers work.
A transducer is a device that converts one form of energy into another. In the case of headphones, this conversion turns electrical energy (the audio signals) into mechanical wave energy (the sound waves).
The way in which the headphones convert energy is dependent on their driver types. We’ll get to each of the 5 main driver types in the section What Is A Headphone Driver? The working principles of the headphone drivers include electromagnetism, electrostatics and piezoelectrics.
It’s important to note that headphones require analog audio (rather than digital audio) to produce sound. This is because analog audio is effectively a continuous alternating current while digital audio is a representation of the analog audio as digital information.
The main takeaway here is that the key feature of headphones is in their ability to convert audio signals into sound. In this way, the headphone drivers are like miniature loudspeakers that are worn close to our ears.
Definitions Of Sound And Audio
We’ve touched on this briefly but let’s now get a bit more detailed in our definitions of sound and audio.
Sound is made of mechanical wave energy. Its vibrations propagate as audible longitudinal waves through a transmission medium (gas, liquid or solid).
The energy of the sound wave causes variations in the localized pressure of the medium. Let’s focus on air as a medium since it is the most common medium for headphones to send sound waves through.
The sound wave causes localized variations in the ambient atmospheric pressure, oscillating through maximum compression and maximum rarefaction.
The amplitude of sound is measured as the amount of pressure variation it causes in a medium. Decibels of Sound Pressure Level (dB SPL) is the most common unit used though Pascals (SI unit) and PSI/PSF (Imerial units) can also be used.
dB SPL is a logarithmic measure of the effective pressure of a sound relative to a reference value of 0 dB SPL at the threshold of human hearing. 94 dB SPL is a common reference point as it matches with 1 Pascal of sound pressure.
Here is a short table to compare dB SPL values with Pascal values. It includes examples of common sound sources that produce each of the levels mentioned:
|dB SPL||Pascal||Sound Source Example|
|0 dB SPL||0.00002 Pa||Threshold of hearing|
|10 dB SPL||0.000063 Pa||Leaves rustling in the distance|
|20 dB SPL||0.0002 Pa||Background of a soundproof studio|
|30 dB SPL||0.00063 Pa||Quiet bedroom at night|
|40 dB SPL||0.002 Pa||Quiet library|
|50 dB SPL||0.0063 Pa||Average household with no talking|
|60 dB SPL||0.02 Pa||Normal conversational level (1 meter distance)|
|70 dB SPL||0.063 Pa||Vacuum cleaner (1 meter distance)|
|80 dB SPL||0.2 Pa||Average city traffic|
|90 dB SPL||0.63 Pa||Transport truck (10 meters)|
|100 dB SPL||2 Pa||Jackhammer|
|110 dB SPL||6.3 Pa||Threshold of discomfort|
|120 dB SPL||20 Pa||Ambulance siren|
|130 dB SPL||63 Pa||Jet engine taking off|
|140 dB SPL||200 Pa||Threshold of pain|
Sound is also defined by the frequency in which it vibrates. The human range of audible frequencies is universally defined as being 20 Hz – 20,000 Hz. Hz (Hertz) is a measure of cycles per second.
The wave illustrated above is a sine wave which represents a single frequency. In the vast majority of cases, sounds are composed of many frequencies acting together. These additional frequencies include harmonics, noise, and other sounds in the environment.
In terms of musical pitch, lower notes have lower frequencies and higher notes have higher frequencies. Lower frequency sound waves have longer wavelengths while higher frequency sound waves have short wavelengths.
Frequency and wavelength are related by the following equation:
v = f • λ
v = velocity of sound (which is dependent, though not overly, on the atmospheric temperature and pressure)
f = frequency of the sound (generally between 20 Hz and 20,000 Hz)
λ = wavelength of the sound (generally between
I talk about this more in my article Fundamental Frequencies Of Musical Notes In A=432 & A=440 Hz.
Here is a table from that post that relates frequency to wavelength (along with musical notation), assuming a sound velocity of 343.2 m/s which is the speed of sound in air at standard atmospheric temperature and pressure (20°C and 101,325 Pa).
|Musical Note||Fundamental Frequency||Fundamental Wavelength|
|E0||20.602 Hz||16.659 m
|F0||21.827 Hz||15.724 m
|F#/Gb0||23.125 Hz||14.841 m
|G0||24.500 Hz||14.008 m
|G#/Ab0||25.957 Hz||13.222 m
|A0||27.500 Hz||12.480 m
|A#/Bb0||29.135 Hz||11.780 m
|B0||30.868 Hz||11.118 m
|C1||32.703 Hz||10.494 m
|C#/Db1||34.648 Hz||9.9053 m
|D1||36.708 Hz||9.3495 m
|D#/Eb1||38.891 Hz||8.8247 m
|E1||41.203 Hz||8.3295 m
|F1||43.654 Hz||7.8618 m
|F#/Gb1||46.249 Hz||7.4207 m
|G1||49.000 Hz||7.0041 m
|G#/Ab1||51.913 Hz||6.6111 m
|A1||55.000 Hz||6.2400 m
|A#/Bb1||58.270 Hz||5.8898 m
|B1||61.735 Hz||5.5592 m
|C2||65.406 Hz||5.2472 m
|C#/Db2||69.296 Hz||4.9527 m
|D2||73.416 Hz||4.6747 m
|D#/Eb2||77.782 Hz||4.4123 m
|E2||82.407 Hz||4.1647 m
|F2||87.307 Hz||3.9310 m
|F#/Gb2||92.499 Hz||3.7103 m
|G2||97.999 Hz||3.5021 m
|G#/Ab2||103.83 Hz||3.3054 m
|A2||110.00 Hz||3.1200 m
|A#/Bb2||116.54 Hz||2.9449 m
|B2||123.47 Hz||2.7796 m
|C3||130.81 Hz||2.6237 m
|C#/Db3||138.59 Hz||2.4764 m
|D3||146.83 Hz||2.3374 m
|D#/Eb3||155.56 Hz||2.2062 m
|E3||164.81 Hz||2.0824 m
|F3||174.61 Hz||1.9655 m
|F#/Gb3||185.00 Hz||1.8551 m
|G3||196.00 Hz||1.7510 m
|G#/Ab3||207.65 Hz||1.6528 m
|A3||220.00 Hz||1.5600 m
|A#/Bb3||233.08 Hz||1.4725 m
|B3||246.94 Hz||1.3898 m
|C4||261.63 Hz||1.3118 m
|C#/Db4||277.18 Hz||1.2382 m
|D4||293.66 Hz||1.1687 m
|D#/Eb4||311.13 Hz||1.1031 m
|E4||329.63 Hz||1.0412 m
|F4||349.23 Hz||982.73 mm
|F#/Gb4||369.99 Hz||927.59 mm
|G4||392.00 Hz||875.51 mm
|G#/Ab4||415.30 Hz||826.39 mm
|A4||440.00 Hz||780.00 mm
|A#/Bb4||466.16 Hz||736.23 mm
|B4||493.88 Hz||694.91 mm
|C5||523.15 Hz||656.03 mm
|C#/Db5||554.37 Hz||619.08 mm
|D5||587.33 Hz||584.34 mm
|D#/Eb5||622.25 Hz||551.55 mm
|E5||659.26 Hz||520.58 mm
|F5||698.46 Hz||491.37 mm
|F#/Gb5||739.99 Hz||463.79 mm
|G5||783.99 Hz||437.76 mm
|G#/Ab5||830.61 Hz||413.19 mm
|A5||880.00 Hz||390.00 mm
|A#/Bb5||932.33 Hz||368.11 mm
|B5||987.77 Hz||347.45 mm
|C6||1046.5 Hz||327.95 mm
|C#/Db6||1108.7 Hz||309.55 mm
|D6||1174.7 Hz||292.16 mm
|D#/Eb6||1244.5 Hz||275.77 mm
|E6||1318.5 Hz||260.30 mm
|F6||1396.9 Hz||245.69 mm
|F#/Gb6||1480.0 Hz||231.89 mm
|G6||1568.0 Hz||218.88 mm
|G#/Ab6||1661.2 Hz||206.60 mm
|A6||1760.0 Hz||195.00 mm
|A#/Bb6||1864.7 Hz||184.05 mm
|B6||1975.5 Hz||173.73 mm
|C6||2093.0 Hz||163.98 mm
|C#/Db7||2217.5 Hz||154.77 mm
|D7||2349.3 Hz||146.09 mm
|D#/Eb7||2489.0 Hz||137.89 mm
|E7||2637.0 Hz||130.15 mm
|F7||2793.8 Hz||122.84 mm
|F#/Gb7||2960.0 Hz||115.95 mm
|G7||3136.0 Hz||109.44 mm
|G#/Ab7||3322.4 Hz||103.30 mm
|A7||3520.0 Hz||97.500 mm
|A#/Bb7||3729.3 Hz||92.028 mm
|B7||3951.1 Hz||86.862 mm
|C8||4186.0 Hz||81.988 mm
|C#/Db8||4434.9 Hz||77.386 mm
|D8||4698.6 Hz||73.043 mm
|D#/Eb8||4978.0 Hz||68.943 mm
|E8||5274.0 Hz||65.074 mm
|F8||5587.7 Hz||61.421 mm
|F#/Gb8||5920.0 Hz||57.973 mm
|G8||6271.9 Hz||54.720 mm
|G#/Ab8||6644.9 Hz||51.649 mm
|A8||7040.0 Hz||48.750 mm
|A#/Bb8||7458.6 Hz||46.014 mm
|B8||7902.1 Hz||43.431 mm
Note that, because sound is made up of frequencies, it also has phase. We can also measure sound in many ways by it interaction with its environment through the study of acoustics and by its interaction with our brains by studying psychoacoustics. These deeply complex studies are beyond the scope of an article on how headphones function.
The air molecules vibrate about their resting place at certain frequencies and amplitudes. As the sound wave passes our ears and bodies, the vibrating air molecules interact with our ears and some of the vibrational energy is even transferred into our bodies (this is most obvious when feeling high-amplitude low-frequency sounds).
Sound is caused by a vibrating object that effectively causes outward sound waves within its medium. These waves are sensed by our sense of hearing (and to some extent, our sense of touch).
Audio is made of electrical energy and is essentially an electrical representation of sound. With audio, we can effectively record, amplify, manipulate and playback sound so long as we have the proper storage, amplifiers, processors and transducers to do so.
Headphones are one of the transducers that allows audio to be created as sound waves.
Audio, too, is defined by both amplitude and frequency (and, therefore, phase). Sound waves produce increases and decreases in localized pressure. The “waves” of audio signals are due to the nature of the alternating current that makes up audio signals.
The frequencies of audio are the same as sound. Our main concern is in the range of 20 Hz – 20,000 Hz.
The amplitude of audio signals is generally given as a voltage (root mean square) or decibels relative to a voltage. Common units include:
- Millivolt (mV): one-thousandth of a volt.
- Volt (V): the difference of potential that would drive one ampere of current against one-ohm resistance.
- Decibels in reference to 1 volt (dBV): a logarithmic measure of voltage relative to 1 volt.
- Decibels in reference to 0.775 volts (dBu): a logarithmic measure of voltage relative to 0.775 volts.
To learn more about audio signals in terms of electricity, check out my article What Is A Microphone Audio Signal, Electrically Speaking? This article focuses on mic signals but applies to all analog audio signals.
Note that digital audio is analog audio/sound recorded in, or converted into, digital form and is not used to drive headphones.
Proper headphones take audio signals and effectively convert them into sound signals, maintaing the frequency response and relative amplitudes.
For more information on the differences between sound and audio, check out My New Microphone’s article What Is The Difference Between Sound And Audio?
What Is A Headphone Driver?
We’ve discussed headphones as transducers quite a bit in this article. The headphone driver is the transducer element of the headphone and is ultimately the most important part.
The headphone driver is designed as part of an electrical circuit that passes the audio source signal when the headphones are properly connected to an audio source (MP3 player, smartphone, audio interface, headphone amp, etc.).
Headphone drivers are designed to react to the alternating current audio signals in a way the effectively produces sound that mimics the characteristics of the audio signal.
Headphones can be designed with one driver for single-ear use. We see this in some headset designs. However, the vast majority of headphones are built with two drivers (one for each ear) and are wired to reproduce stereo audio.
Though the vast majority of headphones and earphones have moving-coil dynamic drivers (which we’ll get to shortly), there are 5 headphone drivers worth mentioning to fully understand how headphones work:
Let’s get into each of these in more detail to improve our comprehension of how headphone drivers work.
To learn more about headphone drivers, check out my articles What Is A Headphone Driver? (How All 5 Driver Types Work) and What Is A Good Driver Size For Headphones?
Moving-Coil Dynamic Headphone Driver
The moving-coil dynamic driver is by far the most common type of driver in headphones. It converts electrical audio signals into mechanical sound waves via electromagnetic induction.
Let’s begin with a simplified cross-sectional diagram of the moving-coil headphone driver:
The key components of the moving-coil dynamic headphone driver are:
- Voice-coil (moving-coil)
- Magnetic structure (magnets + pole pieces)
As we can see in the above diagram, the voice-coil is attached to the diaphragm. This means that as the voice-coil moves, so too does the diaphragm.
The diaphragm is a thin membrane that is nearly always circular in shape and the voice-coil is wound of electrically conductive wire (often copper).
The voice-coil is a cylindrical coil of wire suspended within a cylindrical cutaway in the magnetic structure without ever touching the magnetic structure. The magnetic structure is designed to have its north pole to the interior of the voice-coil and the south pole to the exterior of the voice-coil.
The odd shape of the magnetic structure is achievable via a main magnet and magnetic pole piece assembled together in the following manner:
The main magnet is a ring magnet with its south pole facing upward and its north pole facing downward. These main magnets are often made of strong rare earth Neodymium but can be made of other magnetic material as well.
A ring-shaped pole piece is attached on top of the main magnet to extend its south pole. A plate-shaped pole piece is attached to the bottom of the main magnet to extend the north pole with a cylindrical pole piece shooting up out of it.
This shape allows the voice-coil to be suspended in the empty space. By having opposite magnetic poles to the immediate interior and exterior of the coil, we maximize the magnetic field strength across the coil’s wire and, therefore, optimize the efficiency of the electromagnetic induction required to transduce the audio signal into sound.
All of these components are housed together in proper driver housing.
Here is a picture of two moving-coil dynamic headphone drivers:
So how do moving-coil dynamic headphone drivers work?
Each of the two ends of the voice-coil is connected to lead wires that connect to the audio source. This effectively completes a circuit with the audio device when the headphones are properly plugged in and allows the audio signal to flow through the voice-coil.
More information on headphone audio signal transfer can be found in the upcoming section Additional Information On Headphone Audio.
As alternating current flows through the voice-coil, it produces a coinciding electromagnetic field due to electromagnetic induction. The variation of the magnetic field strength and direction mimics that of the audio signal.
This alternating magnetic field interacts with the permanent magnetic field of the driver, causing attraction and repulsion between the coil and magnet which results in the voice-coil oscillating in a manner that imitates the audio signal.
As discussed, the voice-coil movement pushes and pulls a diaphragm which, in turn, moves air to create sound waves.
The Beyerdynamic DT 990 Pro (link to check the price on Amazon) is an example of moving-coil dynamic headphones.
The Beyerdynamic DT 990 Pro is featured in My New Microphone’s Top Best Open-Back Headphones Under $200.
Beyerdynamic is featured in My New Microphone’s Top 13 Best Headphone Brands In The World.
To learn more about moving-coil dynamic headphones, check out my article The Complete Illustrated Guide To Moving-Coil Dynamic Headphones.
There are also microphones that utilize moving-coil cartridges. To learn more about these mics, check out my article The Complete Guide To Moving-Coil Dynamic Microphones.
Planar Magnetic Headphone Driver
Planar magnetic headphones also transduce energy on the principle of electromagnetic induction and can be referred to as dynamic, too.
Planar magnetic headphones have been around since 1976 with the introduction of Yamaha’s Orthodynamic headphones. To this day, some still refer to planar magnetic headphones as “orthodynamic headphones.”
Let’s start our discussion of planar magnetic headphones with a simplified cross-sectional diagram:
As we can see from the above diagram, the key components of planar magnetic headphone drivers are:
- Magnets (on both sides of the diaphragm in a spaced array)
- Conductive traces (embedded on the diaphragm)
As we can see in the simplified diagram, the magnets are set up in specific arrays on either side of the diaphragm. There are multiple thin bar magnets to each side of the diaphragm with space between them to allow sound to escape from the driver.
The magnets are set up so that the empty spaces between magnets on one side match up with a magnet on the other side. The poles of the magnets change on the same plane as the diaphragm and are opposite on opposite sides.
Unlike the moving-coil dynamic driver mentioned earlier which has a large conductive coil attached to its diaphragm, the planar magnetic “dynamic” driver has its conductive element embedded on the diaphragm itself. The conductive wire is very thin and flat, like the diaphragm, and is embedded in a serpentine fashion onto the diaphragm.
Here is a picture to show the serpentine conductive traces in a planar magnetic diaphragm:
So how do planar magnetic headphone drivers work?
Electrical lead wires connect to either end of the embedded conductive traces. These wires effectively complete an electrical circuit with the audio source when the headphones are properly plugged in.
As the audio signal’s alternating current flows through the diaphragm’s conductive traces, a coinciding electromagnetic field is produced around the diaphragm.
The magnetic arrays to the front are rear of the diaphragm are set up to present a specific and concentrated magnetic field around the diaphragm. This permanent field reacts with the induces field of the diaphragm. The diaphragm will be magnetically attracted to one array and repelled by the other. As the current changes direction, so too does the movement of the diaphragm.
This results in a diaphragm movement that produces sound in a way that mimics the audio signal. Since the magnetic arrays have physical space between the magnets, the sound waves can effectively propagate from the driver.
The Audeze LDC-4 (link to check the price on Amazon) are an example of planar magnetic headphones.
Audeze is also featured in My New Microphone’s Top 13 Best Headphone Brands In The World.
For more information on planar magnetic headphones, check out my article Complete Guide To Planar Magnetic Headphones (With Examples).
Balanced Armature Headphone Driver
Balanced armature headphone drivers are also dynamic and work on the principle of electromagnetic induction. These drivers are miniature and are only found in earphones (particularly in-ear monitors).
Balanced armature drivers are notorious for their limited frequency response and many in-ear monitors require several BA drivers to effectively reproduce the entire audible range of frequencies.
To better understand how balanced armature headphone drivers work, let’s have a look at a simplified cross-sectional diagram:
So we can see that there are more parts in the BA design than in the other headphone driver types. They are:
- Conductive coil
- Drive pin
- Case & sound outlet
The BA driver, like the moving-coil dynamic drive, has a conductive coil or wire. However, this coil is not attached to the diaphragm and is not designed to move as a direct consequence of an applied audio signal.
Rather, this coil is wrapped around an armature that is balanced (hence the name) between a magnetic structure that has opposite poles to the top side and bottom side of the armature.
It is not the coil that is designed to move but the armature. This armature is mechanically coupled to a movable diaphragm via a drive pin. As the armature moves, so too does the diaphragm.
The case is an important feature that protects the sensitive components of the BA driver. Balanced armature drivers are full enclosed in a case except for a tiny opening called the sound outlet that allows the sound produced by the armature to propagate through the air.
Here is a picture of what balanced armature drivers look like:
So how do balanced armature headphone drivers work?
As we’d expect by now, there are lead wires that attach to each end of the conductive coil. These lead wires allow for an electrical circuit between the driver and the audio source when the headphones are plugged in.
The audio signal is an alternating current. When this AC signal is applied to the coil, it causes an associated changing electromagnetic field in and around the coil.
The balanced armature is also electrically conductive and since the coil is wrapped around it, the coil’s changing magnetic field is extended through to the armature.
As we’ve discussed, the armature is balanced with magnets above and below it and it does not require much force to move. These magnets produce opposite magnetic fields at the top and bottom of the armature.
As the audio signal indirectly alters the magnetic field of the armature, the magnets “push” and “pull” the armature up and down according to the audio signal.
As the armature moves, the diaphragm, connected by the drive pin, moves in tandem and produces sound waves.
So by two degrees of separation, the audio signal’s effect on the coil causes the diaphragm to produce sound that is representative of the audio.
The Shure SE535 (link to compare prices on Amazon and B&H Photo/Video) are an example of triple-driver balanced armature headphones.
The Shure SE535 is featured in My New Microphone’s Top Best Balanced Armature In-Ear Monitors Under $500.
To learn more about balanced armature earphones, check out my article The Complete Guide To Balanced Armature IEMs/Earphones.
Electrostatic Headphone Driver
Electrostatic headphone drivers, as their name suggests, do not transduce energy via electromagnetic induction but rather work on electrostatic principles.
This headphone type is fairly uncommon but can deliver incredibly accurate results and pristine sound quality.
In order to function properly, electrostatic headphones require specialized amplifiers that boost the voltage of the audio signal to seemingly extreme levels. These amps also often proivde the DC biasing voltage that is required of the conductive diaphragm.
For that reason, our simplified diagram of the electrostatic headphone driver has its amp/power source included:
So what are the key elements in an electrostatic headphone driver? They are:
- Stator plates
- DC biasing supply (external)
- Amplifier (external)
Similar to the planar magnetic driver, the electrostatic driver has its diaphragm sandwiched between two perforated “plates.” That where the similarities end, though.
The diaphragm of the electrostatic driver is conductive and designed to hold a fixed electric charged. To the front and back of the diaphragm are perforated stator plates which are designed as a sort of parallel-plate capacitor. The diaphragm is electrically insulated from the stator plates via spars around its perimeter.
Other than the housing (including the necessary damping), that pretty much sums up the physical components of the actual electrostatic driver.
In order to function properly, though, the driver must be connected to a specialized amp.
These amps vary in their design but nearly all include, at some point, a step-up transformer that will effectively drive up the voltage of the signal while simultaneously dropping the current. Of course, there are active amplification components as well (including tubes and/or transistor circuits) but the transformer is a common component that drives up the voltage to usable levels.
Here is a picture of an electrostatic headphone driver:
So how do electrostatic headphone drivers work?
First, the amplifier takes the audio signal and cranks up the voltage. A headphone signal strength of 100 to 800 volts is not uncommon when it comes to driving electrostatic headphone drivers. These voltage levels, by the way, would fry each and every dynamic headphone driver.
The bias voltage on the diaphragm of the electrostatic driver could be in the same range.
It’s important to note that the voltages can be incredibly high so long as the current is low due to the incredibly high impedance of electrostatic drivers.
The amplifier effectively boosts the voltage and drops the current of the audio signal to properly drive the driver while also providing the bias voltage for the diaphragm.
The output of the amplifier is connected to the stator plates of the electrostatic driver. An electrical circuit is completed with the stator plates acting as a capacitor.
As the high voltage audio signal applies a positive charge on one stator plate, it applies an equal but opposite charge on the other stator plate.
The positively-charged diaphragm, at any instant, is attracted to one of the stator plates and repelled by the other. This attraction/repulsion is flipped as the alternating current of the audio signal changes. Therefore, the diaphragm will move according to the audio signal and produce sound waves that mimic the audio signal.
To learn more about headphone power requirements, check out my article How Do Headphones Get Power & Why Do They Need Power?
The STAX SR-007A MK2 (link to check the price on Amazon) are an example of electrostatic headphones.
The STAX SR-007A MK2 is featured in My New Microphone’s Top Best Electrostatic Headphones.
Stax is featured in My New Microphone’s Top 13 Best Headphone Brands In The World.
For more information on electrostatic headphones, check out my article Complete Guide To Electrostatic Headphones (With Examples).
There are also microphones that utilize electrostatic transducers. To learn more about these mics, check out my article What Is A Condenser Microphone? (Detailed Answer + Examples).
Electret Electrostatic Headphone Driver
Electret electrostatic headphone drivers work in exactly the same way as regular electrostatic headphones except for the fast that their diaphragms are already charge via electret material.
Electret material (a portmanteau of electric and magnet) maintains a quasi-permanent electric charge. When electret materials are used in conjunction with electrostatic diaphragms, we may forego the need for an external bias voltage.
The electret diaphragm will effectively be permanently charged. Simply apply the high voltage audio signal to the stator plates and the diaphragm will produce sound as intended.
The STAX SR-40 are an example of electret electrostatic headphones.
Electret technology is also used in microphone designs. To learn more about electret condenser mics, check out my article The Complete Guide To Electret Condenser Microphones.
Magnetostriction (Bone Conducting)
The fifth and final headphone driver type we’ll be discussing is the relatively unknown magnetostriction (bone conducting) driver.
This driver works on piezoelectric principles and focuses on vibrating our skulls and inner ears to produce the sensation of hearing rather than on producing sound waves for our ears to hear. “Vibrating our skulls” may seem rather intense but our inner ears convert these vibration into perceived sound all the time.
With a bone conduction driver, we have a piezoelectric crystal that accepts the audio signal from the source and vibrates accordingly.
When this crystal is pressed against our jaw or cheekbones (or other bones in our head), it transmits its vibration to our inner ears which then convert these vibrations to electrical signals that our brains understand as sound.
The AfterShokz Aeropex (link to check the price on Amazon) is a great example of a bone conduction headphone.
The AfterShokz Aeropex is featured in the following My New Microphone articles:
• Top Best Wireless Earphones For Running Under $200
• Top Best Bone Conduction Headphones
For more info on bone conduction headphones, check out my article The Complete Guide To Bone Conduction Headphones (With Examples).
Additional Information On Headphone Audio
So we know that headphones require audio to produce sound. We know that electrostatic headphones require audio signals with extremely high voltage and low current. What else should we know about how headphones work with audio?
This question is loaded with many answers that are beyond the scope of this article. I will provide you with separate My New Microphone articles that discuss the important questions about headphone functioning here:
How do headphones receive their audio?
Headphones typically receive unbalanced stereo via TRS or TRRS cables to drive each of their drivers separately. However, there are other standards to get audio to headphones.
To learn more about what kinds of audio signals headphones need and how they receive them, check out my articles What Is A Headphone Amplifier & Are Headphone Amps Worth It? and An In-Depth Look Into How Headphone Cables Carry Audio.
What factors are most important in headphone design?
There are plenty of important factors in headphone design. Driver type and form factor are two critical parts of headphone design that we’ll discuss in detail in this article.
However, when it comes to the electric specifications of headphones, the frequency response, impedance and sensitivity are all important factors to consider.
To learn more about headphone frequency response, impedance and sensitivity, check out the following My New Microphone articles:
• What Is Headphone Frequency Response & What Is A Good Range?
• The Complete Guide To Understanding Headphone Impedance
• The Complete Guide To Headphones Sensitivity Ratings
How The Different Varieties Of Headphones Work & Fit
Whew, we’ve made it through the complicated part of explaining just how headphones work. There’s still more to know (and more complexities to know) which we’ll get to in this section.
We’ve discussed drivers and how headphones work with audio. Now let’s go through the various form factors of headphone/earphone design.
Supra-Aural (On-Ear) Headphones
Supra-aural headphones are designed to sit on your ears. They are typically cheaper, lighter and less noise-cancelling than their over-ear counterparts.
The Grado SR80e (link to compare prices on Amazon and B&H Photo/Video) are an example of supra-aural (on-ear) headphones. They have moving-coil dynamic drivers.
The Grado Labs SR80e is featured in the following My New Microphone articles:
• Top Best Moving-Coil/Dynamic Headphones Under $100
• Top Best Open-Back Headphones Under $100
• Top Best Supra-Aural (On-Ear) Headphones Under $100
Grado Labs is yet another brand featured in My New Microphone’s Top 13 Best Headphone Brands In The World.
Circumaural (Over-Ear) Headphones
Circumaural headphones have a cup-like form factor that fit around your ears, pressing against your head. These headphones are among the most bulky but provide superb noise-cancellation when combined with a closed-back design.
The Audio-Technica ATH-M50x (link to compare prices on Amazon and B&H Photo/Video) are an example of circumaural (over-ear) headphones. They have moving-coil dynamic drivers and are circumaural in fit.
The Audio-Technica ATH-M50x is featured in the following My New Microphone articles:
• Top Best Headphones For Podcasting Under $200
• Top Best Circumaural (Over-Ear) Headphones Under $200
• Top Best Moving-Coil/Dynamic Headphones Under $200
Audio-Technica is also featured in My New Microphone’s Top 13 Best Headphone Brands In The World.
Closed-back headphones have a solid ear cup that does not let air or sound penetrate. These headphones generally have the best passive noise-cancellation; increased bass response due to the closed-off nature of the cup, and are bulkier and more expensive.
The Sony MDR-7506 (link to compare prices on Amazon and B&H Photo/Video) are an example of closed-back headphones. They have moving-coil dynamic drivers and are circumaural in fit.
The Sony MDR-7506 is featured in the following My New Microphone articles:
• Top Best Headphones For Podcasting Under $100
• Top Best Closed-Back Headphones Under $100
• Top Best Circumaural (Over-Ear) Headphones Under $100
Open-back headphones have slits/perforations that allows air and sound to enter and exit the headphone cups freely.
These headphones often sound wider and truer than closed-back headphones but do not provide nearly as much isolation for sound entering and exiting the cans.
The Audeze LCD-X (link to compare prices on Amazon and B&H Photo/Video) are an example of open-back headphones. They have planar magnetic drivers and a circumaural fit.
The Audeze LCD-X is featured in My New Microphone’s Top Best Planar Magnetic Headphones.
For a detailed read on open and closed-back headphones, check out my article The Complete Guide To Open-Back & Closed-Back Headphones.
In-Ear Headphones (Earphones)
Earphones and in-ear monitors are placed inside the ear canal and ideally created a seal at the canal to couple the driver and eardrum.
When coupled, the diaphragms of the earphones are much more efficient at producing perceived loudness and bass in the listener’s ears.
The Westone UM Pro 30 (link to compare prices on Amazon and B&H Photo/Video) are an example of in-ear monitors/headphones. They have three balanced armature drivers (per earphone) in passive crossover network.
To learn more about the distinguishing factors of earphones and headphones, check out my article What Are The Differences Between Headphones And Earphones?
Earbuds are the loose-fitting consumer-grade earphones that sit inside our ear canals.
They are not nearly as good at noise-cancellation as their in-ear monitor counterparts and often have worse audio quality. The main benefit is that they’re cheap.
The Apple EarPods (link to compare prices on Amazon and B&H Photo/Video) are an example of earbuds. They have moving-coil dynamic drivers.
Apple is featured in My New Microphone’s Top 14 Best Earphone/Earbud Brands In The World.
How Do Wireless Headphones Work?
To fully understand headphones, we should have a comprehension of how wireless audio transmission works. I do not forsee the trend of wireless headphoens stopping anytime soon so it’s good information to have.
Wireless headphones, unlike wired headphones, receive audio signals from their connected audio sources wirelessly.
More specifically, the wireless receiver within the headphones’ receives the wireless audio signal (embedded in a radio signal or an infrared signal known as the carrier signal) from a transmitter and uses that audio signal to drive the headphone drivers.
Here are the basics of how wireless audio transmission works.
First we have the transmitter. This could be a standalone unit or, more commonly, any device that has Bluetooth capabilities.
The transmitter effectively embeds the audio signal within a carrier signal that is either a radiofrequency signal (common) or an infrared signal (rare). Both analog and digital audio signal may be embedded within these carrier signals.
Analog wireless headphone transmission typically works on frequency modulation, in which the audio signal is encoded in the carrier wave by varying the instantaneous frequency of the wave.
Note that Bluetooth is a standard that transmits digital audio via radiofrequency carrier signals in the frequency range of 2.400 to 2.485 GHz. Bluetooth works on phase-shift keying (PSK) digital modulation which transmits data by modulating the phase of a fixed frequency carrier wave. The particular transmitting frequency changes 1,600 every second while maintaining the connection and the transmission of the digital audio signal.
The transmitter then sends these carrier waves through the air (or another medium) to a receiver. Radio and infrared waves travel similarly to sound waves only at much greater frequencies which are imperceptible to human ears.
The receiver inside the headphones effectively accepts the wireless signal and decodes the original audio signal. This audio signal is then fed through an amplifier (and digital-to-analog converter if need be) in order to be brought up to a level that can properly drive the headphone drivers.
After the internal amp, wireless headphones are pretty much the same as wired headphones.
The Bowers & Wilkins PX7 (link to compare prices on Amazon and B&H Photo/Video) are an example of wireless (Bluetooth) headphones. They are feature active-noise cancelling technology. Their design is closed-back circumaural and they have moving-coil dynamic drivers.
The Bowers & Wilkins PX7 is featured in the following My New Microphone articles:
•Top Best Wireless Headphones Under $500
• Top Best Closed-Back Headphones Under $500
• Top Best Circumaural (Over-Ear) Headphones Under $500
• Top Best Noise-Cancelling Headphones Under $500
True Wireless Earphones
True wireless earphones are not connected by any wires or head/neck bands.
These user-friendly earphones work the same as regular wireless headphones except that ear earpiece has its own wireless receiver.
The Bang & Olufsen E8 3.0 (link to compare prices on Amazon and B&H Photo/Video) are an example of true wireless (Bluetooth) earphones. They have moving-coil dynamic drivers.
To learn more about wireless headphones, check out the following My New Microphone articles:
• How Bluetooth Headphones Work & How To Pair Them To Devices
• How Do Wireless Headphones Work? + Bluetooth & True Wireless
How Do Noise-Cancelling Headphones Work?
When we talk about noise-cancelling headphones, we’re talking about headphones with active noise-cancelling circuitry. This is because all headphones have some degree of passive noise-cancellation that stems from the fact that they physically block some sound from entering the ear.
Active noise-cancelling headphones actually measure the amount of noise with a built-in microphone and process this mic signal into an anti-noise signal that is then added to the intended headphone audio to be sent to the driver.
In proper noise-cancelling designs, each earcup has its own microphone and active-noise circuit that shifts the phase and amplifies the mic’s signal.
Feedforward ANC headphones have microphones to the exterior of the ear cups while feed-back ANC headphones have microphones to the interior of the ear cups. Hybrid systems use mics inside and outside the earcup for the best results.
Closed-back circumaural headphones procide the best passive noise-cancellation and are the best candidates for being improved by active noise-cancellation.
The Bose 700 (link to compare the prices on Amazon and B&H Photo/Video) are an example of noise-cancelling headphones. On top of active noise-cancelling technology, the Bose 700s are also wireless (Bluetooth). They have moving-coil dynamic drivers and a closed-back circumaural fit.
To learn more about noise-cancelling headphones, check out my article How Do Noise-Cancelling Headphones Work? (PNC & ANC).
Do headphones sound better than earbuds? Generally speaking, high-end headphones sound better than high-end earphones. However, sounding “better” is subjective and there are certainly in-ear monitors that sound better than cheap headphones.
How do headphone jacks work? Headphone jacks work by connecting the audio signal from an audio device to a compatible headphone cable that will properly carry the audio signal to the headphone drivers. Headphone jacks are the female ports in which headphone plugs connect to. Within the jack, there are multiple conductive pins to transfer the analog audio to where it needs to go.
For everything you need to know about headphone jacks, check out my article How Do Headphone Jacks And Plugs Work? (+ Wiring Diagrams).