Technical Description – Headphone

Be it on the subway or the street there is bound to be someone with a headphone on. At first glance, the headphone can be described as a tiara in its shape although it has a drastically different purpose. The headphone is made of two mini speakers connected with a headband. Headphones were made to provide people with their private sound stereo. In other words, headphones are electroacoustic transducers, which convert electricity to sound, or you can simply see them as mini speakers.

Headphones were first made to allow people to catch events through audio they are not able to attend. Nathaniel Baldwin created a prototype in 1910 and the U.S Navy jumped to claim some of his products. Although many could see the potential of the headphone it never took off because it had poor sound quality. It wasn’t until John C. Koss created the first stereo headphones in 1958 which allowed for commercial use. Previously only professionals in the communication industry would use headphones.

Most headphones are made of four parts. The most noticeable part is the headband. The headband serves to connect the two speakers and provide comfort while securely holding the headphone to the head. The headband is usually made of a plastic or metal strip that is covered with soft cushioning. The strip design was made to be light to not provide discomfort. The soft cushioning is usually foam-covered with leather or cheap textiles. Most headbands also have extensions that allow you to customize the position of the speakers. The speakers are made of three principal parts: magnet, an electromagnetic coil, and cone (diaphragm). The speaker allows the user to hear the sound by transferring electrical signals into mechanical waves (sound waves). The cable is made of wires wrapped around by non-conductive material (usually rubber). The cable acts as a road for the electrical signals to reach the speakers from a device. Some headphones are wireless meaning instead of a cable they have a wireless signal receiver (infrared or radiofrequency). The last part of a headphone is the headphone plug (not a jack). There are three sizes for headphone plugs: 2.5 mm, 3.5 mm, 6.35 mm. The reason for the differences in size is the applications. 6.35 mm plugs are used for professional audio machines. Some of these machines are headphone amplifiers, audio interfaces, and mixing consoles. 3.5 mm plugs are the most common since most consumer products are made for them. 2.5 mm plugs are rare and mostly only seen in some video cameras and walkie-talkies.

Speakers convert electrical energy into mechanical energy(soundwaves) with magnetism. To understand this process, we need to answer what is sound. Sound waves are vibrations that pass through a medium. These vibrations are measured in cycles or frequencies (Hertz). High pitched sound has higher frequencies and vice versa. We can hear sound when the sound waves hit our eardrums which convert the energy into electrical signals into our brain. Humans can hear from the range of 20 Hz to 20 kHz, and the diaphragms in the speakers vibrate in this range to produce audible sound. My PeohZarr headphones support 20Hz-20KHz meaning it has the entire range for human hearing. Along with frequency are sensitivity and impedance. Impedance is the resistance a circuit has against alternating currents. The lower the impedance the more efficient and loud the headphone is. Low impedance ranges from 16 to 32 ohms, while high impedance ranges from 100 to 600 ohms. My headphone has an impedance of 32 ohms with an error of 10 percent. This puts it around the range of low impedance headphones. Old audio devices have extremely high impedance and only new devices have low impedance. It is important to match the impedance otherwise audio quality is affected. Sensitivity is how efficient the headphone is at converting electrical signals to sound. My headphone has 106dB±3dB S.P.L at 1kHz which stands for sound pressure level at 1kHz. This means my headphone can have an effective S.P.L of near 109 dB which is near the volume of a dance club (not recommended for over 30 minutes). These headphone specifications are important to realizing the type of product it is meant to be used for. My headphone is meant for everyday use because of the low impedance (modern usage) and the range of frequency.

Most headphones use the moving coil design to produce vibrations in the diaphragm. Electromagnetic induction states that when an electrical current goes through a conductor a magnetic field develops around it. This force field interacts with the magnet in the speaker to produce an oscillating motion between the voice coil and diaphragm. So, when the electrical signal is passed into the headphone a magnetic field is created which interacts with the magnet. The magnets cause the voice coil to move up and down creating vibrations on the diaphragm.

There are two main types of headphones: circumoral and supra-aural. Circumoral headphones surround the ear with the ear cup. This type of headphone is used to block out outside noise. It’s great for only listening to music without any distractions. It’s usually heavy ranging up to one pound. Thus, most professionals or enthusiasts use this type of headphone.

Supra-Aural headphones press onto the ear. It has more leakage in noise, although it makes up for that in size and weight. The cheap supra-aural headphones tend to be more uncomfortable due to the pressure applied to the ears.

There are also open and closed-back headphones. Open-back headphones allow for more ambient sound resulting in a more natural sound. This is used by musicians to hear how their music would sound. Closed-back headphones offer less ambient noise resulting in better bass.

The headphone might seem to be a basic contraption with speakers attached. However, it can go further when examined in the mold. The best headphones fit beautifully over people’s heads and provide the best listening experience. The headband acts as the bridge for the entire machine and seeks to remain taut. The speakers attach themselves to the headband and place themselves right on the ear. The headband provides access for wires to connect both speakers and the cable. Sometimes the wires are seen if the headphone has an extension. The cable starts from one of the speakers allowing one direct connection with the plug. Along the cable, there might even have a mini microphone. Lastly, the plug connects with a device allowing the signals to travel through the cable into the speakers. Four simple parts to achieve a complex task for our daily convenience.