In this golden age of technology, headphones come in all size and are almost as important as your phone charger for some of us. Going from your over the top headphones to the minuscule in-ear headphones, they all have the same basic innards. Headphones come in really handy for a bunch of reasons from privacy to sound clarity amongst other things.
So how exactly are headphones able to transport sound from your devices to your ear or reproduce sound stored on that storage card? You can consider headphones have small speakers that play sounds directly to your ear.
What are headphones made of?
The first step to knowing how anything works is to know what they are made of. For headphones, the basics include a cable whether detachable or not connecting the headset to your device. Also, there is a part called the driver that is the most important and where its similarity with speakers is more pronounced. Take a look at the driver of a headset and speaker below.
Here is a headset driver by the left and a speaker driver by the right.
That said, the way speakers works are similar to headsets than you can imagine, which is why if you know about speakers, you will probably know how a headset works. Back to how the headset works, we will be looking at how each component helps the headset to achieve its function.
Cable/ Bluetooth chip
Wired headset either use an auxiliary cable or a one-way audio jack fixed to the headset at the other end. In any case, the cable suplies electric current from your device to the headset. This electric current is then converted to sound waves by the driver through a series of processes. The cable serves as the intermediary between the headset and whatever device you are using. The media file is stored in the form of 1’s and 0’s which represent the actual sound that was recorded, be it a podcast, audiobook, music etc.
Furthermore, your smartphone or laptop’s DAC (Digital to Analog Converter). controls the behaviour of the electrical signal that passes through the cable, which can then be interpreted by the driver to produce the sound you hear. It can also mean an increase/decrease in volume or application of certain equalizer settings on your device.
For Bluetooth headsets, there is no cable rather you have a Bluetooth chip in your headset. Instead of transmitting in the form of electrical current as it is in wired headphones, audio/sound is conveyed wirelessly as a Bluetooth signal. However, compression might occur before transmission which raises another issue about audio quality but that is beside the point.
In wireless headphones, your device DAC is not needed considering the Bluetooth signal is a digital signal already.. Although, the DAC will be in the Bluetooth headphones to convert the rf signal to the electric signal that goes into the driver.
This is where most of the work is done pertaining to actually producing sounds. It receives the electrical signal which arrives at the electromagnetic coil and then polarity changes producing sound be it in speakers or headphones.
The driver itself is made up of different components which are basically the coil, magnet and diaphragm. However, not all drivers have all three but the diaphragm and coil are constant components of the headset driver.
Moving on to how they look, the diaphragm is usually made of a thin membrane that uses mechanical vibrations to produce sound waves The coil supplies the energy and is usually responsible for stimulating the diaphragm.
The driver is housed in the earcup and its design is often different from one headphone to another. Basically, how these earcups are designed that decide if a headphone is open back or closed back. We have close back headphones which are enclosed and open back headphones which are exposed allowing air to enter.
The two designs have their different advantages. close back headphones reduce sound leakage while open back headphones allows air in which can then be vibrated to give a richer sound. In open back headphones, noise from the surrounding can easily penetrate and sounds from the headset can easily leak to the surrounding which might annoy people around you. None of this happens in close back earcups.
In music studios, they normally use open back headphones because of its tendency to produce a richer sound which is why they are in a soundproof booth to avoid interference by outside noise considering it is susceptible to
outside noise. These are six different types of drivers you can find in headset:
● Planar magnetic driver
● Electrostatic driver
● Dynamic driver
● Balanced armature driver
● Magnetostriction driver
● Hybrid driver
Planar magnetic driver
This type of driver works by using an electromagnetic coil and magnet to make the diaphragm produce sound. The diaphragm has very tiny coils laid out across it. A bunch of magnets are situated behind the diaphragm to electromagnetic field and electricity is passed through the wires on the diaphragm.
As this happens, the polarity of the coils changes causing them to get attracted and repelled by the magnet repeatedly thereby vibrating the diaphragm and producing sound.
This is one of the cream de la cream of drivers, as it is often suggested to be the type of drivers high-end headphones use. It takes an entirely different approach because it does not use a magnet to move the diaphragm.
Instead, the diaphragm itself is made up of a thin sheet of charged material. This is situated between two electromagnetic plate having opposite
charges i.e. one is positive, the other is negative. When electric current is supplied by the cable into the electromagnetic plate, the polarity changes causing the diaphragm to vibrate thereby displacing the air around it and producing sounds. The electrically charged sheet the diaphragm is made of is thinner than air. So, it doesn’t disrupt the sound produced.
This is one of the most common types of driver for headsets and it is likely to be the one in your headset. It is similar to what you have in the above driver only that the electromagnetic coil is placed in a groove in the magnet.
The electric current conducted through the cable is delivered directly to the electromagnetic coil which makes the polarity change making them vibrate. Since it is attached to the diaphragm on the other end, the diaphragm begins to vibrate also and sound is produced.
In a few words, these drivers often work in the same way except for some few differences here and there. The electric current supplied by the cable changes the polarity in the driver which inadvertently causes the diaphragm to vibrate thereby producing sound waves that travels to your ears. Since sound waves can’t travel in a vacuum, and air is the medium, more air in the diaphragm leads to a richer sound. As in the case with open back
headphones but at the expense of sound leakage which is why close back headphones are preferred by some.
Balanced armature drivers
This is a different type of driver that is used in your typical small pointed tip buds type of headsets. The driver has a rod often called the armature with a coil wrapped around it and a magnet on both sides.
The diaphragm is attached to the armature at one end and once electric current is passed through the coil, the polarity of the armature changes causing it to vibrate and in turn makes the diaphragm produce sound.
This is more like a newer technology and it conducts sound through the bone which is why it is otherwise known as bone conduction driver. It conducts sound directly to your inner ear through the bone leaving the eardrum none the wiser.
You can easily hear ambient sounds from the surroundings and it works for certain people with hearing problems.
Hybrid Drivers They say two heads are better than one, right? So, that is exactly what this is about, using two types of drivers together in a headset. This involves the use of both balanced armature drivers and dynamic drivers
Since balanced armature drivers are not so good with bass, the dynamic driver is sure to complement and bring out a better sound altogether.
How do noise-cancelling headphones work?
As technology advanced, headphones were able to do more than just produce sound and noise cancelling became a thing. So it is only fitting that we also look at how it is able to this.To an extent, medium to big headphones covers most part of the ear which cancels some of the noise from your environs but not all.
On the other hand, there is active noise cancelling which is what we really want to discuss here. This means the headphone electronically cancels noise coming from your surrounding so you can have a seamless listening experience. This especially comes in handy when you’re maybe on a train, plane, bus or in public and want to eliminate outside noise interference.
You might be wondering, how is a headset able to cancel noise? Well, it is simple. As you know, sound is a wave and like all other type of wave, it has properties like frequency, amplitude, and wavelength. A noise-cancelling headset has a microphone that picks up sound waves coming from your surroundings and then generates a sound wave with equal but opposite wave properties (frequency, amplitude and wavelength) and this sound wave is said to be out of phase.
When the sound waves from the surrounding (which is noise in this case) seep into your ear, the sound wave produced by the headset cancels it out because they in anti-phase where destructive interference occurs.
Also, noise-cancelling usually comes with the requirement of having to use an additional battery to power this function. However, there have been reports that the noise-cancelling tech in some headphones tend to make disturbing sound while it works.
Conclusion The whole science behind how a headset works is pretty straight forward and besides the differences from one model to another, there is usually a common denominator involved. Sound requires a medium to be conveyed and in most headset apart from the bone-conducting ones, that medium is air. Just to be clear, sound can travel in solids and liquid as well although it is slower in those mediums.
Sound is produced when a disturbance causes the distortion of particles around it leading to its compression and rarefactions as it travels away from the source. Just like when you have ripples spreading after you throw a stone (disturbance) into the water. The pattern of this disturbance is recorded and stored as a digital file.
When this digital file is played, the sound is reproduced by your headset after passing through the DAC which has to convert it to an analog signal first. The DAC might be in the headset or the device you’re playing from. However, Bluetooth and USB headsets have their own DAC since they both receive a digital signal.
Much of the work lies on how the drive is able to reproduce the disturbance that produced the sound that was recorded at the first place. For audiophiles, you will want to get a headphone that is able to recreate the sounds stored in the media file without any distortion or omission of sound.