Earphones, headsets, and Earpieces are a pair of conversion units that take radio signals from a media player or receiver and convert them into audible sound using speakers close to the ear. The earphone can be separated from the media player, and can be connected only with a plug. It can listen to the sound alone without affecting others. It can also block out the sound of the surrounding environment, which is very helpful for people who use in noisy environments such as recording studios, bars, travel and sports. Headphones were originally used for phones and radios, but with the popularity of portable electronic devices, they are used for mobile phones, walkmen, radios, portable video games and digital audio players.From the development of the audio industry as a whole, wireless earphones are still a new thing, the development time is not long, in the rising period, user demand is constantly improving, users' expectations of wireless earphones are also improving, which is a new test for the industry. Some of the most important concerns for users include sound quality, battery life, wireless transmission capability and data latency. In terms of data, the wireless transmission capacity can basically meet the needs of the vast majority of users, while the sound quality and endurance capacity still have great potential for improvement. If we improve from these two points, we believe it will be easy to attract users' attention in the future. Headphones are the symbol of people's portable sound system. There are two types of headset standards: OMTP, which is often called the national standard, and CTIA, which is called the international standard. Earphones are classified according to their energy exchange modes, which mainly include moving coil mode, moving iron mode, electrostatic type and equal magnetic type. In terms of structure and function, it can be divided into semi-open and closed. There are earplug type, hanging ear type, in-ear type and headwear type. In terms of the number of wearers, there are single-person headsets and multi-person headsets. From the sound source difference, can be divided into active earphones and passive earphones; Active headphones are also often referred to as plug-in headphones. Moving coil earphone is the most common and common earphone. Its driving unit is basically a small moving coil speaker, and the diaphragm connected to it is driven by the voice coil in the permanent magnet field to vibrate. Moving coil type earphone efficiency is relatively high, most can be driven by the earphone output on the stereo, and reliable and durable. Generally speaking, the larger the diameter of the driving unit, the better the performance of the headset. In consumer headphones, the maximum diameter of the driving unit is 70mm, which is generally flagship ear muzzle type headphones. They are headphones that vibrate and sound through a finely constructed connection rod that is transmitted to the center of a tiny diaphragm. Moving iron headphones can easily fit in the ear canal due to their much smaller unit size. This effectively reduces the area of the inner ear and allows for the deeper part of the ear canal. The geometric structure of the ear canal is much simpler than that of the auricle, which belongs to the circular type. Therefore, a soft silicone sleeve can play a better sound insulation and sound leakage prevention effect compared with traditional earplugs. Loop iron earphone is a moving coil moving iron hybrid drive sound earphone, single moving coil + single moving iron, single moving coil + double moving iron structure, the advantages of the moving iron unit lies in the electroacoustic conversion efficiency is high, light vibration body, so high sensitivity, good transient performance, so that the moving coil difficult to show the music dynamics, instant details highlighted. Low frequency and medium frequency are naturally presented by the moving coil unit, giving play to the advantages of good low frequency extension of the moving coil and full and natural transition of the middle frequency. The advantages and functions of the moving iron unit mainly undertake and supplement the high-frequency attenuation section of the moving coil. Starting from the frequency division point of 6kHz, the moving iron unit is responsible for the high frequency and extends the high frequency range to 30kHz.