Electroacoustic product testing typically uses a 1000Hz (1kHz) signal as a standard reference for several reasons:

1, the sensitivity of the human ear: in the normal range of hearing, the human ear is most sensitive to the sound of the middle frequency band, about 1kHz to 4kHz. This range roughly corresponds to the basic frequencies of human language. Using a test signal of 1kHz can provide a reference standard that meets the perception of most human ears.

2, simplify the test: In the performance test of many electro-acoustic equipment, in order to reduce the variable, usually only a single frequency signal is used, and 1kHz is just in the middle of the frequency range of human hearing. This ensures that reasonable measurements are obtained in most cases.

3, industrial standards: This has been adopted by various international and national standards, such as IEC and ANSI. Therefore, the design and testing of most electroacoustic products will be carried out in accordance with this standard.

4, the linear response of the device: the frequency response of most audio devices at 1kHz is linear, that is, the relationship between input and output is linear, without too much distortion. This makes 1kHz an ideal test signal.

5, the most important point: on the hearing curve of the human ear, 1000Hz (1kHz) is a special frequency point, and it is also an internationally recognized standard hearing frequency. At 1kHz, the relationship between sound pressure level and perceived loudness is defined as linear, that is, at this frequency, our perception of sound loudness is directly corresponding to the sound pressure level.

The perception of sound pressure levels by the human ear is not linear at all frequencies. At other frequencies, especially in the low and high frequency parts, the human ear's perception of the sound pressure level will have different degrees of deviation, which is the so-called nonlinearity. The sensitivity of the human ear to different frequencies is described by the isobaric curve (isobaric pressure level curve), which all converge at 1kHz.