headphone
Headphones are small speakers that emit sound directly at the ear. The speakers are housed in padded housings and attached to an elastic headband. The padded housings enclose the ears and prevent extraneous noise from entering, as well as sound from escaping to the outside. To improve playback quality and reduce extraneous noise, many headphones work with active noise compensation, Active Noise Cancelling( ANC).
Headphones are characterized by high sound quality. They have two speakers, one for each ear. To hear stereo sound on the right side, the headphones must be put over the corresponding ear. The speakers can be dynamic voice coil speakers, but also electrostatic speakers. The latter can only be operated with an amplifier.
The operation of headphones can be wired, but also wireless with radio technologies and battery operation. The wired headphones have a jack plug as a connector, the wireless ones can be connected via Bluetooth or other wireless technologies.
The most important characteristics of headphones
The impedance of headphones is often around 50 ohms, but in some cases it can vary greatly from this value. Impedances of 5 ohms to 250 ohms are quite realistic, and there are also headphones with high-impedance impedance of up to 1 kilo-ohm. The impedance values say nothing about the playback quality. This is generally very high, which is due to the relatively amplitude- level frequency responses. The radiated frequency range extends from the lowest frequencies of below 20 Hz to beyond the listening range of 20 kHz. It should be noted that the level drops rarely exceed 3 dB in the entire audible range. Only at the cutoff frequencies, which are no longer audible to normal listeners, can the sound level drop by up to 10 dB.
A smaller version of the headphone is the earphone. The combination of a headphone with a microphone is called a headset.