Yes In summer, I am most afraid of mosquitoes. It's too heavy to smoke insecticide, and it's no fun to raise mosquito nets. Then, some people began to ponder "bad tricks." A friend of the author saw a program on a TV channel about using speakers to drive away mosquitoes. He felt good and downloaded the mosquito repellent software introduced in the program. My friend used it all night and didn't sleep well at all. He repeatedly adjusted the volume of the speaker after getting up, which affected his rest. When the noise is too loud, I am afraid it has no mosquito repellent effect. As a result, it didn't work all night, and mosquitoes were still buzzing around the house. After listening to my friend's one-night experience, the author was really in distress situation. I have explained this matter to you before, and I will tell you the mystery this time. So, how did a friend fall into this "bad trick" trap? Let's take a look at the following introduction first. A network company in South Korea recently launched a "computer mosquito-repellent incense", which can let people surf the Internet with peace of mind and relieve the suffering of mosquito bites. Empas, Korea's main portal, launched a service to drive away mosquitoes by radio waves on the 24th, the Korea Times reported on the 25th. This service drives away female mosquitoes in the breeding season by letting the computer emit sound waves with a frequency of 200 to 600 Hz. In nature, male mosquitoes do not suck blood, and only female mosquitoes bite people and animals to suck blood when breeding. According to reports, users can download the "computer mosquito-repellent incense" anti-mosquito software for free as long as they register on empas website. After the computer is turned on, the software runs automatically without adding new accessories. Because people's ears can't hear the frequency emitted by the computer driven by anti-mosquito software, using this software has no effect on people. A few days ago, SKT, a Korean mobile service provider, also launched an anti-mosquito ringtone service, which uses the same principle as "computer mosquito repellent incense". What we saw above is the mosquito repellent software released abroad, and the author also searched some domestic mosquito repellent software with similar "efficacy" on the Internet. According to the description of an electronic mosquito-repellent incense software, it can make sounds that imitate the natural enemies of mosquitoes-dragonflies and bats, creating a noisy environment that annoys mosquitoes and keeps them away. Moreover, this kind of sound is inaudible to people and has no influence on the human body. The slogan of some software is even more vowed: "Let mosquitoes give up and run away!" Seeing this, it is estimated that everyone will have a question in their hearts. This is a lot of red mouth and white teeth. So, are these mosquito repellent softwares useful? Are they harmful to us? The author will discuss this topic with you below. Principle of mosquito repellent software: ultrasonic wave? Many net bugs who like surfing the Internet late at night have been bitten by mosquitoes, and everyone is looking for a good way to repel mosquitoes. There are many softwares on the Internet, such as mosquito repellent, electronic mosquito repellent KM300V2.0, Super Mosquito King, Yitian electronic mosquito-repellent incense and electronic mosquito-repellent incense. In the download introduction of some mosquito repellent software, it reads: "A new generation of intelligent broad-spectrum mosquito repellent software! The intelligent broad-spectrum mosquito repellent software developed according to the principle of bionics sends out the sound with the same frequency as the natural enemy dragonfly, bat or male mosquito through the computer to achieve the mosquito repellent effect. " Some mosquito repellent software said: "This product emits high-frequency sound waves, not electromagnetic waves, so it is harmless to people's health. Please feel free to use it! " Do you understand, no matter what kind of software, it is ultimately necessary to "strike" mosquitoes with sound through the computer, and the speaker is the terminal component to realize electronic mosquito repellent! So what is the "high frequency sound wave" mentioned above? This so-called "high-frequency sound wave" is actually "ultrasonic wave". "Ultrasonic wave" means that when the frequency of sound exceeds the frequency limit of human hearing, people will not realize the existence of sound, so this high-frequency sound is called "ultrasonic wave". In fact, friends who like earphone products should know that the hearing limit of human ears is between 20 Hz and 20000Hz, which means that as long as the speaker can emit sound waves higher than 20000Hz, mosquitoes can be driven away. This sounds feasible in principle, but can it be realized on the speaker? After careful thinking, the question is not difficult to figure out: can our common multimedia speakers play this "high-frequency sound wave"? This has to start with the manufacturing principle of the speaker. The sound box is made according to the sound characteristics and the auditory characteristics of the human ear. Sound has three basic characteristics, namely frequency, intensity and sound spectrum. These three characteristics are subjectively perceived by human ears as tone, intensity and timbre. The number of times an object vibrates per second is called frequency. Generally speaking, the faster an object vibrates, the higher its frequency, and the higher the tone we feel. The slower an object vibrates, the lower its frequency, and the less tones we feel. But the human ear can't hear the vibration of all objects, and the vibration frequency of objects is too low or too high for the human ear to feel. Simply put, the speaker is designed based on this feature. Common multimedia speakers are composed of sound generating units in various frequency bands. Due to the limited working range of different types of units, a set of speakers is equipped with at least three parts: bass, midrange and treble. After all, the tweeter unit of a loudspeaker is not a high-frequency sound wave generator, just as the bass unit can't perfectly express the low-frequency sound effect, the tweeter unit can't emit too much ultrasonic waves, and when working in the ultrasonic section, although the upper limit of some tweeters can reach 30000Hz, the working state and efficiency of the loudspeaker will be greatly reduced. That is to say, ordinary multimedia speakers above 18000Hz are rarely attenuated.

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