It is the "locator" for EQ regulation, determining which "frequency band" of the sound you need to adjust. The unit of sound frequency is Hz (Hertz). Different frequencies correspond to the "pitch" and "sound type" that the human ear hears, and are directly related to the core characteristics of the sound (such as human voice, bass, and treble).

1. The correspondence between frequency and sound characteristics

The audible frequency range of the human ear is approximately 20Hz to 20kHz. The frequency division of EQ regulation is highly matched with this range, and the sound functions of different frequency bands vary significantly:

2. The key logic of frequency regulation

• “Find the problem and then make the adjustment”
  ：First, listen to the defect of the current sound (such as "muffled vocalism" → it might be due to an excessive 150Hz or insufficient 2kHz), and then locate the corresponding frequency instead of blindly boosting a certain frequency band.
• “It is not widely targeted”
  ：For instance, if you want to optimize the human voice, prioritize the 150Hz to 5kHz (the core frequency band of the human voice) rather than overly adjusting the 20Hz to 40Hz (subwoofer) to avoid interfering with irrelevant sounds.
• Device/scene adaptation
  ：The "frequency response shortcomings" of different devices vary (for instance, TWS headphones tend to have excessive low frequencies, and live microphone mid frequencies are prone to blurring). It is necessary to determine the frequency in combination with the characteristics of the device.

It is the "dynamometer" for EQ regulation, determining whether to "enhance" or "weaken" a certain frequency, with the unit being dB (decibels), directly affecting the "volume" and "presence" of the sound in that frequency band.

1. The adjustment logic and effect of Gain

The adjustment range of Gain is typically -12dB to +12dB (some professional devices can reach ±18dB), and positive and negative values correspond to completely different effects:

2. The core principle of Gain regulation

• “Minor fine-tuning”
  ：The core of EQ is "correction" rather than "reconstruction". Each adjustment should be made in units of ±1dB to ±2dB, and repeated listening should be conducted to avoid making large adjustments at once (such as directly increasing by 10dB, which may disrupt the sound balance).
• “Listening experience takes priority”
  ：The Gain value is for reference only. The final value should be based on "human ear comfort" (for example, the same + 3dB, different people have different sensitivities to mid and high frequencies, so it needs to be adjusted as needed).
• “Linkage frequency”
  ：After boosting a certain frequency band, if new problems arise (such as muffled sound after boosting the bass), the associated frequency band should be simultaneously attenuated (such as by 150Hz), rather than adjusting a single parameter separately.

III、Q value (Quality Factor, quality factor)

It determines the "width of the range" of EQ adjustment, that is, when you adjust a certain frequency, how many surrounding frequency bands will be "affected along with it", which is directly related to the "accuracy" of the adjustment.

Key function combination usage tips

1. Live voice optimization
   ：HighPass (cut-off at 80Hz, noise reduction) + Peak (attenuation at 300Hz±2dB, nasal noise reduction) + HighShelf (8kHz+1.5dB, clarity enhancement)
2. The bass is enhanced when listening to music
   ：LowShelf (80Hz+2dB, overall bass boost) + Peak (60Hz+1dB, enhanced subwoofer elasticity)
3. Noise reduction processing
   ：HighPass (cut off 100Hz, eliminate low-frequency noise) + Notch (attenuate 50Hz/-15dB, eliminate AC interference)

The core logic of these functions is“first, filter out the interference (HighPass/Notch), and then optimize the listening experience (Peak/LowShelf/HighShelf)）”，When making adjustments, it is necessary to take into account the characteristics of the equipment (headphones/microphones/speakers) and the actual scene to avoid over-tuning which may cause sound distortion.