EMI filter in headphones: what it is and what it is for

Electromagnetic interference

Electromagnetism in electronic devices spreads within a range (field) that surrounds this device and the key factor of these is the electrical voltage with which they work. The higher the voltage, the more intense the surrounding magnetic field and the interference it can cause.

EMI filter function

Explained inside, EMI filters are designed to counteract the influence of electromagnetic fields generated by external devices and avoid their interference. These types of filters have quite different uses:

Power supply filtering Noise suppression in audio circuits Motor control Sensor management Actuator management

In this article we focus on those belonging to the second category: noise suppression. These interferences are responsible for generating problems that interrupt or degrade the quality of our audio and the intensity and range of the same varies according to the devices. It is also common that the closer we are to the electronic apparatus that originates them, the more severe are the effects that their magnetic interferences cause. Another possible origin is that both devices are connected to the same electrical outlet.

How does the EMI filter work?

EMI filters are designed to have an impedance identical to that of the circuit in the band pass frequency range of the signal. Its structure consists of a passive inductor, a resistor, and capacitor components that create a filter capable of suppressing a frequency band of signals in a circuit. These filters can have many different types of internal configurations depending on the passive components used and their structure. The most common formats in which they usually appear are:

PI: parallel capacitor, series inductor or resistor and a parallel capacitor. T: inductor or resistor in series and a capacitor in parallel. RC: series resistor followed by a parallel capacitor. LC: inductor in series followed by a capacitor in parallel.

EMI Filter Types

Within the EMI filters we can find different types of them, whose application and presence in our headphones can vary depending on the model. In general we can find:

Present on the wire

They consist of a cylindrical piece through which the cable passes. Its core or inner lining is ferrite (iron-α), which is one of the crystalline structures of iron and has magnetic properties. The presence of this material nullifies the interferences because it acts as a suppression coil. We usually find this filter located on the cable near the headphones in the case of the 3.5 jack ports. For USB connections we can also find it inside the USB itself.

An advantage of this type of EMI filter is that we can incorporate it into headphones, speakers or other types of devices if noise interference is a problem that you experience frequently. RFI EMI high frequency filter, noise suppressor. Topnisus Brand Cable Clip for Samsung Galaxy S3MINI i8190, 10 pcs Ferrite Core Package includes 10 pcs Ferrite Core.; Use against interference, improve signal and filter. 9.83 EUR A Use: anti interference, improves signal and filter.; Easy to install with double pressure clips. 7.99 EUR RF Choke 31500 Ferrite Core Material 31Mix ID 1/2 "Filter, 13mm The newest 31 mix material technology for the widest range of noise suppression.; 11/2" wire diameter, 13mm

Integrated into earphone

This design allows the cable to be free of additional weight, for example the volume controller or mute button. Here we find a standard EMI filter r with passive inductor, a resistor and capacitor components. This format will usually be found in headphones with a USB connection housed next to the sound card in the headset itself.

The performance of the integrated EMI filters depends a lot on the quality of the manufacturing materials. The key is the information provided by the brand regarding the cancellation of electromagnetic interference present in your product. It is generally common for you to find data regarding noise cancellation, either passive for the headphones or active for the microphone (or active for both). Active noise cancellation and EMI filters are not the same, so keep that in mind.

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Conclusions about the EMI filter

In general, it is often very difficult to escape electromagnetic interference even today if it is sporadic. Our houses are full of household appliances and other devices that create electric fields with a tendency to create conflicts, so if you are lovers of enjoying your music or games in peace, having headphones with an EMI filter is undoubtedly a great idea.

We recommend reading: Best gaming headphones on the market.

The ferrite EMI filter is a great addition to your wired headphones, especially if they are somewhat older models whose wiring insulation is not of very high quality. Those with USB connection and gaming models usually have an integrated cancellation system, but the quality of it is something that always remains in the hands of the manufacturer.

We are generally much more aware of technologies like active or passive noise cancellation, but this is not the only factor that can help noise cancellation in our headphones. In any case, how relevant is the presence of an EMI filter to you? Do you think that active noise cancellation is enough? Leave it to us in the comments!