Impedance:
The impedance of the earphone is the abbreviation of its AC impedance. Its size is the sum of the DC resistance of the coil and the inductive reactance of the coil: z= (R2+ ω 2L2)1/2。
Sensitivity:
The sensitivity of earphones in ordinary times is actually the sensitivity level of earphones. It is the sound pressure level generated by earphones coupled to artificial ears (artificial heads) when 1MW of electrical power is applied to earphones. 1MW of power is calculated based on the standard impedance of earphones at 1000Hz.
Distortion:
The distortion of headphones is generally very small. At the maximum power, the total harmonic distortion (THD) is less than or equal to 1%, which is basically inaudible, much smaller than the distortion of speakers.
Frequency response:
Sensitivity has different values at different frequencies, which is frequency response. The dependence of sensitivity on frequency is represented by a curve, which is called frequency response curve. The human auditory range is 20hz-20000hz, and most people cannot hear the sound beyond this range. The frequency band that headphones can replay is quite wide, and excellent headphones can reach 5hz-40000 Hz.
Diffusion field balance of back mounted headphones:
There are two kinds of equalization methods for headphones: free field equalization and diffusion field equalization. Free field equalization assumes that the environment is non reflective, such as wilderness; Diffusion field equilibrium simulates a room with reflection, and its hearing sense is more natural than free field equilibrium. See iec60268-7 for the method of testing the flatness of diffusion field by the International Electrotechnical Commission. However, the diffusion field equalization is modeled on the standard head shape and room model, which will not satisfy all users and is not suitable for some recordings, such as fake head recordings.
