The root of howling in KTV box is dismantled, and the problem of acoustic feedback is completely solved by microphone collocation.

In KTV entertainment scene, audio howling is the most common equipment failure problem that affects the experience. Whether it is a commercial chain KTV, a private luxury karaoke room or a family audio-visual box, there are problems such as high-frequency howling and intermittent noise feedback after the volume is raised. Most users temporarily avoid the problem by lowering the volume and weakening the sound effect, which not only greatly weakens the sound quality and atmosphere of K songs, but also can't solve the problem from the root. Long-term howling will also damage the high-pitched unit of the audio and cause equipment loss. This paper comprehensively analyzes the problem of KTV howling from five dimensions: acoustic principle, fault source, equipment selection, system configuration and on-site debugging, and provides a standardized and landing-proof feedback solution.
First, the core acoustic principle of KTV howling
The professional definition of howling is the phenomenon of acoustic feedback self-excitation, which belongs to the closed-loop gain out of control of audio signals. Its formation logic is: the microphone picks up the human voice signal, which is amplified by the power amplifier equipment and produced by the sound box. The hard wall, floor and glass in the box form sound reflection, and the reflected sound is recorded by the microphone again, forming an infinite closed loop of "picking-amplifying-reflecting-picking again". When the closed-loop signal gain exceeds the critical threshold of the system, the specific high-frequency frequency will continue to be superimposed and amplified, eventually forming a shrill scream.
The closed and narrow space structure of KTV is the core environmental factor of frequent acoustic feedback. Compared with open venues, the low sound absorption coefficient, dense sound reflection and chaotic sound field superposition are more likely to trigger audio self-excitation, which is the core reason why KTV howling is far more than outdoor performances.
Second, the four core fault sources of KTV howling
1. Microphone directivity accuracy is insufficient.
Low-end miscellaneous microphones generally adopt pan-heart-shaped and pseudo-omni-directional pickup design, and the receiving angles are scattered, so it is impossible to focus on the main body of human voice. The equipment will simultaneously record invalid sound sources such as speaker sound, spatial reflection echo, environmental noise floor, etc., and continuously fill the closed-loop gain of audio, which will easily trigger high-frequency howling even at normal singing volume. The core advantage of professional audio equipment lies in accurate directivity adjustment, which can effectively shield the sound field interference in non-vocal areas and cut off the acoustic feedback path.
2. Wrong selection of pickup equipment and unbalanced sensitivity adaptation.
Some users blindly pursue high-resolution sound quality and use large diaphragm condenser microphones in closed KTV scenes. The condenser microphone has ultra-high receiving sensitivity, which can capture all-dimensional subtle sounds. In the box without sound insulation treatment, it will completely collect the echo of the speaker, air noise and equipment noise, greatly reducing the trigger threshold of acoustic feedback. The measured data show that in the closed K-song scene, the howling trigger probability of the capacitive microphone is more than three times that of the professional dynamic microphone, which is totally unsuitable for KTV sound field environment.
3. Radio frequency band interference causes audio fluctuation.
The low-end 2.4G universal wireless microphone in the market has weak anti-electromagnetic interference ability. KTV box is integrated with lighting control system, touch-control song-ordering equipment, wireless network and large-screen display equipment, and various electromagnetic signals are superimposed and interfered, which will lead to unstable microphone transmission signals and intermittent current noise. Noise will upset the balance of audio system, accelerate the self-excitation of acoustic feedback, and cause equipment failure with howling and noise alternately.
4. Lack of equipment placement and use specifications
Non-standardized operation is an important factor to induce howling artificially. When singing, the microphone is facing the sound surface of the speaker, multiple microphones are idle at the same time, the microphone is flat to pick up the vibration noise of the desktop, and the singing station is too close to the speaker, which will continue to superimpose the system gain, disrupt the sound field balance, and artificially trigger feedback howling.

Three, KTV microphone standardized selection parameters
1. Pickup type: professional dynamic microphone is preferred.
The dynamic microphone is a special adaptation equipment for KTV scenes, which has the characteristics of low sensitivity and high dynamic margin. It can accurately amplify the close-range human voice, automatically attenuate the distant space reflection sound and speaker echo, and naturally has excellent anti-feedback ability. At the same time, it is tolerant of high sound pressure input, high volume singing, high-pitched explosion scene without sound breaking and distortion, and adapts to the complex sound field of closed box.
2. Directionality: Hypercardioid direction is the best scheme.
Compared with the ordinary cardioid directional microphone, the hypercardiac directional device has a more focused radio reception angle, and the side and rear radio reception attenuation effects are obvious, which can shield the sound field and spatial echo of the speaker to the greatest extent and cut off the closed loop of acoustic feedback from the physical level, and is the core selection standard for preventing howling in commercial KTV.
3. Transmission frequency band: UHF digital wireless frequency band is adopted.
Abandon the 2.4G general frequency band with serious interference, and choose the professional UHF digital audio frequency band. Exclusive independent audio channel can effectively avoid electromagnetic interference of various electronic devices in the box, with stable signal transmission and pure noise floor. Support multiple devices to work in parallel at the same time, and the frequency points are not cross-talk, which meets the requirements of multi-person chorus and multi-camera radio.
4. Hardware structure: double-layer blowout prevention metal net head
Equipped with high-density metal mesh head and double-layer blowout prevention structure, it can effectively filter human voice blasting sound and air jet wheat noise, stabilize the peak value of audio output, avoid high-frequency howling caused by instantaneous audio overload, protect the core components of microphone head, and improve the durability and service life of equipment.
Fourth, the whole scene anti-howling system collocation and landing scheme
1. System equipment collocation
The host computer is equipped with automatic frequency scanning and intelligent frequency locking functions, which automatically scans the blank channel of the box before use, and assigns independent fixed frequency points to each microphone to prevent frequency point intermodulation interference; With professional digital anti-howling processor, it can automatically detect and suppress high-frequency resonance points, broaden the upper limit of audio gain, and realize full-volume singing without howling and distortion.
2. Equipment placement specification
Fixed singing position, the microphone always avoids the radiation area on the front of the speaker, so that the voice pickup end is facing away from the sound generation end of the speaker; The speaker equipment is far away from the core singing area, reducing the direct superposition of sound; The antenna of the receiver is placed vertically and separately, away from metal cabinets, power amplifiers and other equipment to avoid signal attenuation and electromagnetic interference.
3. Standard for daily use
Follow the principle of "turn it on when it is used and turn it off when it is not used", and the idle microphone will be muted or turned off in time to avoid redundant radio overlapping gain; The microphone comes standard with anti-roll accessories to reduce the vibration noise caused by hand-held rotation and flat; Appropriate sound-absorbing soft clothes are installed in the box to optimize the sound field environment and reduce the intensity of spatial echo reflection.
V. Summary
KTV audio howling is not a simple problem of volume and debugging, but a comprehensive failure caused by multi-dimensional imbalance in equipment selection, frequency band transmission, sound field environment and usage specifications. Blindly reducing the volume can't cure the problem, but it will lose the sound quality and experience of K songs. By matching the hypercardiac dynamic microphone and UHF professional transmission frequency band, matching with standardized equipment placement and system debugging, the closed loop of acoustic feedback can be completely cut off, and the feedback howling can be eliminated from the root cause, and the professional K-song sound effect with transparent voice, full volume and no noise can be realized.